A Manual on Corrugated Fiberboard Boxes

A MANUAL ON
CORRUGATED FIBERBOARD
BOXES
WRITTEN BY-
YOGESH PANDEY &
SUSAMOY BHATTACHARJEE
(Indian Institute of Packaging, Mumbai)

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PREFACE
This manual basically is a compilation of a lot of data and information
pertaining to corrugated fibreboard boxes.
Rarely noticed, but always there, corrugated is ubiquitous.Thediry brown
corrugated box that we not only take for grantedm but are in a hurry to dispose
off after it has safely delivered its contents to us, has rarely got its due! This
manual is an attempt to change that.
Without the glamour of plastic, or the new wonder materials of today,
corrugated remains a truly unique and important material, both industrial and
domestic. Today it is one of the most important packaging materials in the
world. One of the reasons corrugated is finding favour in the current issues of
eco-friendliness.
This manual starts with a general introduction to paper and paper making
process thereby moving on to the fibre alingment. This is also packed with the
information related to the manufaturing of corrugated boxes. A brief
information has also been given regarding the various style of boxes, testing
and the various defects of corrugated boxes.
Attempt has been made to include all possible details regarding the corrugated
boxes. Hope the information provided in this manual will be useful to every
reader.

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Contents
S. no. Topics Page no.
1. Introduction 4
2. Brief Introduction about paper 5
3. Components of the corrugated board 17
4. Manufacture of the corrugated box 30
5. Nomenclature of the corrugated box 39
6. Main features of CFB boxes 41
7. Desiging & Style of boxes 42
8. Quality Parameters and their Attributes 57
9. Defects in Corrugated boxes 66
10. Testing of corrugated boxes 73
11. Future trends 91
12. Glossory 93
13. Bibliography 96

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INTRODUCTION
The corrugated industry
Corrugated boxes are everywhere. This simple yet profound packaging
medium is now ubiquitous, having emerged as the largest transport packaging
material.
By the end of the World War I, about 20% of the boxes in USA were
corrugated or solid board, and 80% of wooden construction. By the end of the
World War II, these figures were reversed !
Corrugated is used to pack live chicks, dead fish, dry onions, fresh flowers,
fruits, ball-bearings, sea shells, a complete flowers, fruits, ball-bearings, sea shells,
a complete motorcycle, a single helmet , yarn, clothes, cotton, buttons. You
name a product and a corrugated travels alongside like a dedicated companion.
History of corrugation
In the late nineteenth century (1871), Albert Jones discovered an ingenious
way of giving strength to paper.
In 1874, a fellow American named Oliver Long discovered that when a flat
sheet of paper was glued to one side of the corrugated paper, it kept its shape
even when it was stretched and subjected to pressure.
In 1920, the production speed of the machines increased to 20 m/min then
to 90 m/min in 1940 and 200 m/min in the seventies, finally exceeding 300 m/min
in recent years.

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Brief Introduction about paper
What is paper?
“Matted or felted sheet, usually made of cellulose fibres, formed on a wire screen from
water suspension”.
Or
“A substance in the form of thin sheets or leaves intended to be written or printed on,
or to be used in wrapping. It is made of rags, straw, bark, wood, or other fibrous material,
which is first reduced to pulp, then molded, pressed, and dried”.
Source materials include wood pulp, rags, and recycled paper. The fibres are separated
(by processes that may be mechanical, chemical, or both) and wetted to produce paper pulp, or
stock. The pulp is filtered on a woven screen to form a sheet of fibre, which is pressed and
compacted to squeeze out most of the water. The remaining water is removed by evaporation,
and the dry sheet is further compressed and often (depending on the intended use) coated or
infused with other substances. Types of paper in common use include bond paper, book paper,
ground wood and newsprint, Kraft paper, paperboard, and sanitary paper (for towels, napkins,
etc.).
Paper- Sources of Raw Material
Agricultural Residue Imported Waste Wood Pulp
Bagasse Wheat & Rice Straw
Virgin Kraft

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FIBER LENGTH
Approximate fiber length of cellulose used in paper making.
Long fibres produce paper with proportionately higher:-
 tensile strength
 tear strength
 fold strength
 puncture strength
 a rougher surface texture
 variations in density due to poor formation that can lead to
o uneven ink adsorption during printing
o erratic adhesive bonding
Short fibres produces paper with:-
 a smoother surface, and
 significantly reduced physical properties compared to long fibres
Recycled fibres will have properties inherited from the original fibres source, but
with the provision that every re-pulping process degrades and reduces fibre length, thus
significantly reduced physical properties compared to long fibres, and affected by extraneous
contaminants such as :-
Fiber Source Typical Fiber Length
Main Sources:
Hardwood (e.g poplar, aspen, maple) 2 mm/0.08 in.
Softwood (e.g. pine, spruce, hemlock) 4 mm/ 0.16 in.
Other Sources:
Straw, bagasse < 2 mm/ 0.08 in.
Bast (e.g. linen, cotton) > 2 mm/ 0.5 in.
Recycle paper varies depending on sources

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 water insoluble adhesives
 plastic debris
 non-removable printing inks
Pulping methods
 Mechanical pulping
o mechanical separation of fibres in refiners
 Chemical pulping
o chemical separation of fibres
o alkali sulphate extraction (kraft pulp)
 Combined processes
o semi-chemical (chemicals before refining, NSSC)
o thermo-mechanical (wood softened by heating before mechanical refining)
o chemical-thermo-mechanical pulp (CTMP)
Pulp characteristics- Mechanical pulp
 High yield from the timber
 The presence of lignin makes the fibres hard and rigid.
 Limited degree of consolidation
o Paper with high bulk (low density), bending stiffness and dimensional stability
 A sheet made solely of mechanical pulp is relatively weak but relatively stiff
Pulp characteristics- Chemical pulp
 Preserves fibre length
 Develops a high degree of consolidation (High density)
 Flexible and soft fibres
 Good creasing, embossing and cutting properties
 High whiteness, brightness and light stability properties
 High purity yields good odour and taint protection

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Final paper properties affected by
• Beating of the pulp
• Forming of the fibre network
• Wet-pressing
• Drying and drying constraints
• Post-drying operations such as
– Size pressing (starch solution)
– Surface coating
– Calendaring
Types of paper used in corrugated
industry
KRAFT PAPERS
1. Semi Kraft Paper
2. Virgin Kraft Paper/Kraft paper
(Produced by integrated Pulp & Paper Mills)
3. Multilayer Paper/Kraft liner board
4. Imported Kraft Paper / Liner Board
5. Corrugating Media

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A. Semi Kraft Paper :
 Produced from Agro based raw material, Like Baggase, Kahi, Serkanda & Hessian etc.
 Caustic soda pulping process
 Paper contains residual lignin, Pentose sand other degraded cellulose raw material.
 Due to the presence of these this paper does not have high strength.
 Gets decomposed in strength properties on storage.
 The main properties like Cobb. Tear & Breaking lengths are very poor.
B. Virgin Kraft Paper/produced by integrated Pulp & Paper Mills :
 The Kraft paper produced from forestry based raw material
 This paper contains medium strength,
 Higher GSM paper with higher Burst, and Tear cannot be produced by these mills.
Therefore, this paper is having a limitation in making boxes of higher strength in three ply.
C. Multilayer Paper/Kraft liner board :
 This is produced from imported waste paper.
 Since major quantity of waste paper is from softwood long fibre, paper produced from
imported Waste paper has comparable strength.
 This paper is made on Multilayer paper machine, higher GSM Kraft paper can be
produced having desired Strength Properties

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Paper Making Process
Process Steps of Papermaking:
 preparation of the fiber materials (dissolving, thickening / diluting, refining, cleaning,
mixing)
 addition of pigments and chemical additives (dependent on paper grade)
 sheet or web forming on an endless wire
 pressing between felts & rolls
 drying on steam heated cylinder
 possibly surface application of starch / chemical additives
 smoothing by calendaring
 converting (cutting & forming paper reels, or sheet cutting)
The Fourdrinier Machine is the basis for most modern papermaking, and it has been
used in some variation since its conception. The Fourdrinier accomplishes all the steps needed
to transform a source of wood pulp into a final paper product.
Sections of the paper machine
There are four main sections to the Fourdrinier.
Pulp preparations
Harvested tree trunks are cut into logs of four to eight foot lengths, then sent to a very
large horizontal debarking drum, which rotates and strips the logs bare; or a vertical ring
debarker which removes bark mechanically in a single pass. In some cases, whole tree length
logs can be debarked. The freshly debarked logs are then fed into a chipper, which reduces the
logs to handheld-sized chips. The chips are then passed along to a digester where they are
cooked for a number of hours, a process that softens the wood to a large degree. The digester
can be one of two types: sulfite or sulfate. In a sulfite digester, the principal chemical
constituent is calcium acid sulfite and the method is referred to as the acid process. The sulfate,
or Kraft, process is the younger of the two, and uses an alkaline system that reduces cooking
time.
After the cooking is complete and the lignin content has been removed, the softened
chips are fed at high pressure into refiners where the chips are forced between rotating steel
plates. The refiner plates shatter the chips into a soup of brown fibres. Chlorine is used to
bleach brown fibres to a brighter white colour, and calcium hypochlorite (sulfite process) or
chlorine dioxide (sulfate process) are also used for whitening. Caustic soda (sodium
hydroxide NaOH) (lye) is used to wash the pulp of any impurities, and the steps are repeated
in order to obtain the desired brightness.

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Sections of the paper machine
Diagram showing the sections of the Fourdrinier machine
There are four main sections to the Fourdrinier machine.
1. Fourdrinier forming section(80- 85% water)
2. Press Section(40- 60% water)
3. Dryer Section(5- 7% water)
4. Calender Section

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Fourdrinier forming section (80% water)
The first section is typically known as the wet end. Pulp may be delivered to the
Fourdrinier machine in a slurry form (a mixture of fiber and water) directly from the pulping
process. Alternatively, pulp may be supplied in dried sheets which are then broken down in
water to produce similar slurry, before being fed to the refiners in the wet end where the fibers
are subjected to high pressure pulses between bars on rotating refiner discs. This action causes
the fibrils of the fibers to partially detach and bloom outward. After refining the pulp is mixed
with some of the following: sizing, fillers, colors, retention aid and waste paper called broke to a
stock, and passed on. Washing is done in pressurized screens and hydocyclones and also
deaeration is done.
The stock then enters the headbox, a unit that disperses the stock and loads it onto a
moving wire mesh conveyor with a jet from an opening called the slice. The streaming in the
jet makes some fibres align. This alignment can partly be taken away by adjusting the speed
difference between the jet and the wire. The wire revolves around the Fourdrinier table, from
breast roll under the headbox over the couch to the forward drive roll, foils under the wire are
creating low pressure pulses that will vibrate and partly deflocculate the fibres while water is
removed. Later on Suction boxes below the wire gently remove water from the pulp with a
slight vacuum and near the end of the wire section the couch will remove water with higher
vacuum.

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Major Functions of the fourdrinier forming section:
 Form the sheet of paper by a filtration process
 Dewater the sheet to approximately 20% solids.
Press section (40-60% water)
Large Fourdrinier-style paper-making machine.
The second section of the Fourdrinier machine (or any modern paper machine) is the
press section, which removes the most water via a system of nips formed by rolls pressing
against each other aided by press felts. This is the most efficient method of dewatering the
sheet as only mechanical pressing is required. Press felts historically were made from cotton.
However, today they are nearly 100% synthetic. They are made up of a polyester woven fabric
with thick batt applied in a specific design to maximize water absorption.
Presses can be single or double felted. A single felted press has a press felt on one side
of the press, the sheet being exposed to a felt on one side and a smooth roll on the other.
Double felted is where both sides of the sheet are in contact with a press felt. Single felted nips
are useful when mated against a smooth top roll, which adds a two-sidedness—making the top
side appear smoother than the bottom. Double felted nips increase roughness, as generally,
press felts.
Conventional roll presses are configured with one of the press rolls is in a fixed position,
with a mating roll being loaded against this fixed roll. The felt run through the nips of the

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presser rolls and continues around a felt run, normally consisting of several felt rolls. During the
dwell time in the nip, the moisture from the sheet is transferred to the press felt. When the
press felt exits the nip and continues around, a vacuum box known as an Uhle Box applies
vacuum (normally -60 kPa) to the press felt to remove the moisture so that when the felt
returns to the nip on the next cycle, it does not add moisture to the sheet.
Pickup roll presses are vacuum assisted rolls loaded against plain press rolls (usually a
roll in a centre position). While out of favour, these are generally found in machines built in the
1970s–1980s. Pickup roll presses normally have a vacuum box that has two vacuum zones (low
vacuum and high vacuum). These rolls have a large number of drilled holes in the cover to allow
the vacuum to pass from the stationary vacuum box through the rotating roll covering. The low
vacuum zone picks up the sheet and transfers, while the high vacuum zone attempts to remove
moisture. Unfortunately, centrifugal force usually flings out vacuumed water—making this less
effective for dewatering. Pickup presses also have standard felt runs with Uhle boxes. However,
pickup press design is quite different, as air movement is important for the pickup and
dewatering facets of its role.
Crown Controlled Rolls (also known as CC Rolls) are usually the mating roll in a press
arrangement. They have hydraulic cylinders in the press rolls that ensure that the roll does not
bow. The cylinders connect to a shoe or multiple shoes to keep the crown on the roll flat, to
counteract the natural "bend" in the roll shape due to applying load to the edges.
Extended Nip Presses (or ENP) are a relatively modern alternative to conventional roll
presses. The top roll is usually a standard roll, while the bottom roll is actually a large CC roll
with an extended shoe curved to the shape of the top roll, surrounded by a rotating rubber belt
rather than a standard roll cover. The goal of the ENP is to extend the dwell time of the sheet
between the two rolls thereby maximizing the dewatering. Compared to a standard roll press
that achieves up to 35% solids after pressing, an ENP brings this up to 45% and higher—
delivering significant steam savings or speed increases.
Major Functions of the press section:
 Dewater the sheet to 35- 45% solids
 Consolidate the web
 Decrease the surface roughness

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Dryer section
The dryer section of the Fourdrinier machine, as its name suggests, dries the pulp by
way of a series of steam-heated rollers that stretch the web somewhat, removing the moisture.
Additional sizing agents, including resins, glue, or starch, can be added to the web to alter its
characteristics. Sizing improves the paper's water resistance, decreases its ability to fuzz,
reduces abrasiveness, and improves its printing properties and surface bond strength. Some
paper machines also make use of a 'coater' to apply a coating of fillers such as calcium
carbonate or china clay. Paper leaving the machine is rolled for further processing.
Major Functions of the dryer section:
 Dewater the sheet to 94- 97% solids.
 Set the interfiber bonds.
 Modify the surface characteristics of the sheet.

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Calender section
A calender consists of a number of rolls, where pressure and heat is applied to the
passing paper. Calenders are used to make the paper surface extra smooth and glossy. It also
gives it a more uniform thickness. The pressure applied to the web by the rollers determines
the finish of the paper.
After calendering, the web has a moisture content of about 6% (depending on the
furnish). It is wound onto a roll called a tambour, and stored for final cutting and shipping.

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COMPONENTS OF CORRUGATED BOARD
1. LINERS
2. FLUTING MEDIUM
3. ADHESIVES
4. INK
5. May contain any surface treatment or coating.

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LINERS
In corrugated board, top and bottom liners should be heavier and stronger than the
fluting medium. Internationally, there are separate qualities of paper for either application.
Paper meant for top and bottom liners is very strong and expensive whereas recycled cheap
grade paper is used for fluting medium. Linerboard gives strength, medium gives rigidity and
stiffness.
Broadly, linerboard could be classified into two main categories: Kraftliner, and
Testliner. Kraftliner is made using virgin fibres whereas Testliner is made using recycled fibres.
KRAFTLINERS (VIRGIN LINER or VIRGIN PAPER):-
Kraft liner is that which is made from 100% virgin wood fibres. This is not really true
now, upto 25% recycled content is allowed, though most mills, for technical reasons, are unable
to use more than 10- 15% recycled content. The best kraftliner is made from softwood e.g.
pine, fir, spruce, hemlock, cedar, etc. It has long fibres and gives higher strength to paper
because of more criss crossing of fibres. Kraft means strength in German and Kraftliner is one
with high mechanical strength. It is completely unbleached and made from wood fibres by
Sulphate process.
The natural colour of the product is a shade of brown derived from the wood fibres. It
varies slightly according to the mix of tree species and growing areas. It is popularly known as
Brown Kraft and denoted by abbreviation BK. Bleached Virgin pulp produces White Top liner
denoted as WT. A thin layer of bleached pulp on top of unbleached pulp results in mottled
white linerboard sometimes called oyster white or marble/mottled Kraft denoted as MK. Dyes
can be added to bleached pulp to produce other colours.
Generally linerboard is specified in terms of its basis weight. Basis weight is measured as
weight per unit area. By varying the amount of pulp spread on the mesh, the basis weight of
the paper can be varied.
Kraft liner can be characterized by:
1. Its smooth surface
2. Relatively brighter luster.
3. The burst factor will be more than 35
4. Generally, its RCT (Ring Crush Test) is 0.9 times gsm of the paper divided by 100. Say,
RCT of 200 gsm Kraft liner could be (0.9 x 200)/100= 1.8 KN/m. (This is an approximate
thumb rule and may not be expected to hold good in all cases especially for high
performance liners).

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5. Dirt Content (can be seen as dark black spots) are less and smaller in size.
6. Its moisture absorbing capacity measured as cob value is less (around 30-50 gm /sq
m).
In India paper is made from Baggasse and such other agricultural wastes. It has short fibre
length and high silica content. Being very feeble, this paper offers little strength. While in
advanced countries most of the boxes are 3- ply with 200/150/200 combination, in India, for
the same strength, 5- ply boxes with 150/120/150/120/150 combination are employed. Total
gsm of paper consumed in former case is approximately 600 whereas in latter case it is 775.
Poor quality of paper has resulted in use of 30% additional paper for same strength.
TESTLINERS:
Testliner is made from recycled fibre. It is very difficult to make paper from 100%
recycled fibres because of pulping and beating problems. However, the aim is to use maximum
amount of recycled fiber. The quality of testliner depends on the quality of recycled fibres
(source of recycled fibers) and number of times these fibers have been recycled earlier.
Every time fibers are recycled, their length reduces during pulping and beating
operations. After certain number of recycling, fibers are no longer good enough for making
linerboard.
Testliner is manufactured using the multi-ply process in 2-3 layers from:
 Purely secondary fibers with and additional treatment.
 Secondary fibers and Kraft pulp.
For this reason, there is not always same colour on either sides as well as there can be
significant variation in strength depending upon virgin to recycled fibres ratio. A thin layer of
bleached fibres give mottled or marble testliner (MT). White duplex (WD) is a combination of
whit tip layer and grey bottom layer. Bottom layer looks grey as it is made from the unsorted
paper waste fibers.
Testliner is characterized by:
1. Slightly rough and dull surface
2. The burst factor is around 25-28
3. RCT is almost same as that of Kraftliner.
4. Dirt spots are more but smaller in size.
5. Cobb value is marginally higher. Around 40-60 testliners are becoming increasingly
popular these days because of following reasons

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a. Source reduction: Source reduction is a reduction in dependence on and
depletion of virgin raw materials. The use of recycled materials is a goal of
many box users today. However, for certain food packaging, use of virgin fibers
is recommended.
b. It offers RCT almost same as that of kraftliner. Latest carrier laws emphasize
more on RCT than on BS.
c. Testliner is not as expensive as Kraftliner.
d. It consumes less virgin fibers hence it is more eco-friendly.
HIGH PERFORMANCE LINERS: HIGH DENSITY LINERS
High performance, High density Liners or High Ring Crush Liners are a lightweight grade
of linerboard that has very high Ring Crush Test value. BF is in between 28-30.
These new liners are manufactured on paper machines equipped with the new “High
Intensity Nip Press” also known as the “Extended Nip Press”. These shoe- type hydraulic presses
improve the compression by rapidly removing water from the sheet.
Board with high ring crush liners gives high edgewise compressive test value (ECT). Of
late, high density liners are becoming increasingly popular. However, there are some peculiar
problems with these liners. Because of compact bonding and lesser porosity, these liners do not
absorb glue effectively. This results in poor bonding. Also being dense, they become hot faster,
resulting in brittleness of fibers. Boxes with these liners often exhibit cracking at crease lines.
Use of high performance liners requires change in almost all process variables like viscosity of
glue, temperature, steam etc. this has not made them very popular in box plant
FLUTING MEDIUM
Fluting medium in corrugated board is like bracings in a truss. It should have just enough
strength to connect both the liners without buckling or stretching. Main strength of corrugated
board, however, comes from the liners; this is the reason why recycled fibres are used for
making fluting medium. Generally, in paper mills, material not suitable for liner is used for
manufacturing fluting medium.
Fluting medium can be further classified, depending upon the nature of the recycled
fibers, into three categories: fluting medium (FM), semi- chemical (SC), and schrenz. While
fluting medium is made from fibers of old boxes and other containerboard wastes, Semi-
chemical is made using hardwood like wood-chips etc. and schrenz is made from fibers derived
from general paper waste including domestic wastes.

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The common gsm for fluting medium is 120, 140 and 150. It is characterized by:
 Dull surface with fibrous look.
 BF in the range of 18-22.
 RCT could be (0.4 x gsm)/100.
 It has very high moisture carrying capacity on either side. Cobb value is more
than 100 gsm. This allows efficient glue absorption and penetration.
 Dirt spots are more and prominent.
FLUTE PROFILES:-
The flutes form a series of connected arches. An arch with the proper curve is the strongest way
to span a given space. It can support many times its own weight, especially when the ends of
arch are anchored.
In a corrugated board they are anchored to a facing. At the end, arches from columns.
These structures can support even more load than arches. Although the columns are hollow,
the material is unbroken from top to bottom. Strength is maintained by facings, which hold the
columns perpendicular to stacking pressure.
The flute profile is characterized by:
H: the flute height measured as distance between crest and trough.
P: the flute pitch, measured as distance between two successive crests or troughs.
n: the number of flutes per meter.
m: take up factor.
When a paper having length of one meter is converted into corrugations, its effective length
reduces. Reduction in the length depends upon flute profile. It flutes are broader; reduction in
length would be more. Say, for making 1 meter long C flute, we require approximately 1.4
meter long flat sheet. The coefficient 1.4 is known as the take up factor.
The following table, based on an internationally recognized classification, shows the various
flute profiles in existence with their geometric characteristics

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NOTE: “Take-up factor” is the length of medium per length of finished corrugated board.
K flute (also known as Jumbo flute) is rare and is used in heavy duty boxes. F and N
flutes are recent inclusions in the flute table. They are very small and a corrugated board with N
flute is almost as flat as a solid board. Before the introduction of F and N flutes, corrugated
board was not considered suitable for primary boxes where high quality of printing and
aesthetics are more important than protection to the product. Small flute has the unique ability
to offer structural strength without sacrificing print quality, and many companies now have the
chance to service software and other high- end consumers, previously not attainable by
corrugated industry.
Application of flutes
Selection of an appropriate profile depends on use of the packaging. It is well known
that the broader flutes are used for shipper cartons whereas narrower flutes are used for
primary or smaller cartons.
In this context, it would be interesting to not behavior of flutes in various type of load
situations. During its journey from the packing line to the end user a corrugated box undergoes
various types of load. All these loads can be broadly classified into two categories:
FLUTE PROFILE PITCH (MM) HEIGHT (mm) FLUTES PER
METRE
TAKE UP FACTOR
K - JUMBO 12.0-21.0 6.5-10.0 68-80 1.60-1.80
A - BROAD 8.0-9.5 4.0-4.8 105-125 1.48-1.53
C- MEDIUM 6.8-8.0 3.2-4.0 125-147 1.42-1.50
B- NARROW 5.5-8.5 2.2-3.0 153-181 1.28-1.43
E- MICRO 3.0-3.5 1.0-1.8 285-334 1.22-1.29
F- MINIMICRO 2.0-2.5 0.7-1.0 400-509 1.18-1.21
N 1.5-1.9 0.5-0.7 526-670 1.13-1.18

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a. Load along the flutes. It is measured by Edge Crush Test (ECT)
b. Load perpendicular to flutes. It is measured by Flat Crush Test (FCT)
ECT is proportional to square of the caliper. Broader flute gives more thickness and therefore,
they give higher ECT value. They are used for boxes where higher stacking strength is
important.
During Flat Crush the load comes on to the flute tips. If value of the load is the same
because of lesser numbers of flutes per running meter load on each flute is higher in broader
flutes than that on narrower flutes. Flutes tend to buckle under the load. It is well known that
taller structures are always mores slender and they buckle faster. Broader flutes are taller and
therefore they buckle faster. This makes broader flutes vulnerable to flat load. Broader flutes
have lesser Flat Crush Test (FCT) value than narrower flutes.
During transportation broader flutes get crushed faster. As soon as they are crushed,
thickness of board reduces and ultimately loads carrying capacity (ECT) varnishes. The board
then fails to behave as it was anticipated to. Also a 3- ply box of broader flute is uncommon. If it
is to be used in 3- ply then it is always used with heavy gsm of liner and fluting medium.
Broader flutes are uncomfortable for printing. In modern technology, printing is done after
manufacturing the board. When printing plates are pressed on the top surface of the board,
two phenomena takes place:
1. The top liner tends to deflect in between two successive flute tips.
If all other parameters are the same, the deflection of top liner is a function of
unsupported length is in between two successive flute tips. Broader the flute, more the
span and more the deflection. As a matter of fact, deflection varies to the power of four
of the span. Once the top liner deflects, printing plate loses contact with it and
ultimately it ends up with poor quality of printing. Printing sometimes exhibits bands on
flute tips, dull impressions etc.
2. The flutes tend to buckle.
Because broader flutes buckle faster, sufficient pressure could not be applied resulting
in a very light impression. Should the pressure be increased to obtain sharper and
clearer images, the board get crushed.

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Broader flutes are not comfortable for making fancy geometries because of their higher
stiffness. Very rarely die cut boxes are made using broader flutes. Also broader flutes look less
harmonious with delicate products where aesthetics of the box is also a part of overall appeal.
A Flute
A flute is one of the broadest of all the available flutes. An A fluted board has substantial
thickness and therefore offers highest bending stiffness. Such board when made with heavy
grammage paper can take very high compressive load. The A flute is very uncommon in 3- ply
boxes. It is more commonly used in 5- ply construction with B or C flute on the outer side
C Flute
C flute is replacing A flute for its less paper consumption and caliper. It offers reasonable
stiffness and compressive strength. Its ECT is lower than that of the A flute board, however,
because of tits lesser caliper, its strength in crushing load is much higher. This makes it and
extremely suitable profile to be used in 5 – ply construction. It is generally, provided on the
inner face of the board. It contributes in stacking load bearing and also provides cushioning to
the product inside.
B Flute
B flute is the most popular profile. It is used in 3- ply as well as 5- ply construction. Because of
its lower4 caliper, it has quite high flat crush strength. The flutes can effectively withstand the
pressure of plates during printing operation. The B flute has spacing sufficient enough to
provide reasonable flat crush strength makes it extremely suitable for small sized 3- ply boxes.
It is also put on the outside of 5- ply box.

25
E Flute
This flute has minimum compressive strength (ECT) and maximum crushing strength (FCT). It is
predominant used as primary packaging where printing and aesthetics are more important
compared to strength requirements. The smallest thickness and closely spaced flutes makes it
very suitable for printing operation. It can withstand printing pressure without noticeable
deflection of top liner. E flute is also very comfortable in folding and making fancy geometries.
This makes it versatile for designing attractive packaging or displays.
ADHESIVES
An adhesive is a compound that adheres or bonds two items together. Adhesives may
come from ether natural or synthetic sources. Natural source is always cheaper than synthetic
source. Starch is a natural polymer.
Why starch adhesive?
Starch based adhesives are cheaper than other natural sources i.e Animal Glue, Gilatin,
Fish Glue and they are also abundantly available around the world. Starch is made from the
natural souces like Maize, Tapioca, Potato, With. In Paper Box making Maize and Tapioca
Starches are preferred to use than other starches because of their better adhesive properties.

26
Bond is formed between the adhesive with the adherend (Paper) by the application of light
pressure. Adhesives are designed with a balance between flow and resistance to flow. The bond
is formed because the adhesive wets the surface of adherend. Once the adhesive and the
adherend are in close proximity, molecular interactions involved in the bond contribute
significantly to its ultimate strength.
Characteristics of Starch Adhesives:
1. Solubility:
The starch adhesive must be completely soluble in water without giving any residual matter.
The starch must form a stable suspension in water.
2. Viscosity:
It is most important property of starch adhesive. In general terms it can be visualized as fluidity
of the adhesive. High viscosity means low fluidity and vice versa. It can be measured by many
instruments. Viscosity measured by B4 cup which is the cheapest and simplest way. The unit of
measurement for B4 cup is ‘seconds’. The method is described in ‘Indian Standards’ briefly.
3. Tack:
Tack-adhesion strength should be enough as per application and material.
4. Solid content:
It specifies as amount of soluble active solids material formerly known as ‘Gum Powder’. More
the solid content in liquid gum more will be the strength of bond. So if you want a nice high
strength box simply use high solid content adhesive.
5. Shelf life:
The adhesive should have optimum shelf life.
GENERAL COMPOSITION OF ADHESIVES
The “Stien- Hall” process is the most popular process to make the glue. The glue made by this
process has the following ingredients:
Water: this allows the grains of starch to become hydrated when the heat renders them
gelatinous, developing the adhesive power.
Starch: the viscosity depends on the starch content of the primary solution. The concentration
of the glue is determined by the amount of starch in the secondary solution.

27
Caustic soda: this is used not only to prepare the base but also to lower the gel temp of
secondary starch to 50- 55⁰ C. It also helps the glue be absorbed into the paper thanks to its
wetting effect.
Borax: this increases the initial viscosity of the base and has the effect of considerably
increasing the viscosity produced when the secondary starch becomes gelatinous during gluing.
Formaldehyde: starch is a substance which is liable to ferment. To protect it from bacteria and
yeast, protective agents are added to the glue.
Adhesive formulation:
Each corrugated board manufacturer uses his own glue formula. Here is the general
formulation:
- 76% water
- 21% starch
- 2% formaldehyde
- 0.6% caustic soda
- 0.4% borax
This formula gives the following characteristics:
- Solids- 21%
- Stein- Hall viscosity: 40-50 sec (40-45 on single facer, 45-50 on glue unit)
- Gelatinizing temperature: 50⁰C on single facer, 50- 55⁰C on glue unit at a bath
temperature on the machine of 30-35⁰C.
MECHANISM OF BONDING:
Step 1: The wetting of the paper by liquid gum:
In this step gum spreads uniformly over the surface of paper. It penetrates in the surface
cavities. The viscosity of the starch adhesive is responsible for the wetting.
Step 2: Development of tack:
As the liquid gum spreads on the surface of paper. The water in the adhesive gets absorbed in
the paper (cellulose fiber web) due to applied pressure and surface tension. Thus viscosity of
the starch paste increases and initial bonds are formed. This initial weak bonding is known as
‘Initial Tack’ or ‘Green Bond’.
Step 3: Solidification:
As more and more water is absorbed in web of cellulose, fiber solidification takes place with

28
increase in interaction between molecules of starch and cellulose (paper). This interaction gives
rise to the adhesive bond. These interactions can be classified as
1. Mechanical Engagements
2. Electrostatic Interactions
3. Chemical Interactions
IMPORTANT FACTORS FOR BONDING
Quality of adhesives:
Quality of adhesives is dependent upon the quality and quantity of starch. The adhesive should
must have initial tack and optimum shelf life.
Viscosity:
Viscosity of liquid adhesives should be optimum to achieve right penetration in paper. It also
determines machine speed and is one of the most important factors in board making.
Solid content:
A starch adhesive should have minimum 16% of solid content (Active solid matter). Higher solid
Content gives more tack; lower solid content gives low tack. In order to achieve high strength
bond, 20-25% solid content is sufficient but this value may vary in specific circumstances.
Cobb value:
Absorption capacity or liquid gum penetration capacity of paper.
Application of singlewall, doublewall and triplewall boxes
Single-wall is generally used for either a display dispenser type of a primary box or as a
shipper carton. Generally, for a dispenser type box, E flute board with whit liner is chosen. Box
with this board can be attractively printed. Whereas for shippers carton B flute is chosen.
General gsm configuration is 200/150/200 or 150/127/150. C flute is uncommon as it has
limited flat crush test value. Also it is difficult for die cutting.
Double wall is generally chosen for heavier shipper carton. General flute combination is
BC with gem configuration of 150/127/150/127/150. The BC combination offers best of both
worlds, as B offers sturdy outer surface whereas C offers higher load carrying capacity and
cushioning to the contents inside. Varying the gsm of the liners and fluting medium, wide
spectrum of shipper cartons are covered by this board.
Triple- wall board is used rarely, only for heavy machineries and products with sharp
projections.

29
Manufacturing of CFB Boxes
3 Ply Combined Automatic Corrugated Board Making Plant
1
2
3
4
6
7
12
13
11
10
5
8
9
14
14
14

30
Details of the Parts:-
1. Self loading reel stand - Fluting medium.
2. Corrugator and Glue Applicator (Adaptor/Fingerless) - Formation of the single facer.
Fingerless Gluing unit is used as a modified version.
3. Self loading reel stand - Liner 1
4. Overbridge- post corrugation
5. Self loading reel stand- Liner 2
6. Tension Roller
7. Glue Applicator- Pasting of the third ply
8. Heating cooling and drying chamber
9. Heating plates(nine to ten)
10. Pneumatic valves used for Heating the plates
11. Heavy duty pull unit which is a belt usually made up of Polyester-nylon and can
withstand higher temperature.
12. Rotary Cutter
13. NC Cutter- Pneumatically Controlled Cutter
14. Preheaters which can be maintained at variable temperature.
THE MAIN STAGES ARE:
 BOARD FORMATION IN AN AUTOMATIC LINE
 PRINTING, SLITTING AND SCORING – TRIMING & CREASING THE
BOARD
 SLOTTING – FORMATION OF FLAPS
 MANUFACTURER’S JOINT (1¼ inch): EITHER STAPLED OR GLUED

31
View of an automatic Plant:
3 Ply Combined Automatic Corrugated Board Making Plant

32
REEL UNWINDING SECTION
CORRUGATORS

33
FINGERLESS GLUING UNIT
OVERBRIDGE: POST CORRUGATION UNIT

34
AUTOMATIC DRYING SECTION
ONLINE ROTARY

35
NC- CUTTER
AUTOMATIC STACKER

36
2- COLOR PRINTING, SLOTTING, DIE-CUTTING & STACKING UNIT (Close view)
2- COLOR PRINTING, SLOTTING, DIE-CUTTING AND STACKING UNIT

37
LEAD EDGE PRINTER SLOTTER AND DIE- CUTTER

38
Technical Specifications
5 ply corrugated box making plant:
 High speed bearing mounted corrugation Machine with variable speed drive- 2
nos.
 Drum type heaters: 4 nos.
 Self loading reel stand: 5 nos.
 Triplex heating unit before gluing
 On line duplex pasting unit
 Heating cooling and drying chamber (consist of fourteen hot plates)
 Heavy duty pull unit
 On line creasing and slitting unit
 Heavy duty cut off unit
3 ply corrugated box making plant:
 High speed bearing mounted corrugation Machine with variable speed drive
 Drum type heaters - 2 nos.
 Self loading reel stand- 3 nos.
 Duplex heating unit before gluing
 On line simplex pasting unit
 Heating cooling and drying chamber (consist of nine hot plates)
 Heavy duty pull unit
 On line creasing and slitting unit
 Heavy duty cut off unit

39
Nomenclatue of Corrugated
fiberboard
Single Face Corrugated Board or 2-Ply board :
Singlewall Corrugated fiberboard or 3-Ply board:

40
Doublewall Corrugated fiberboard or 5-Ply board:
Triplewall Corrugated fiberboard or 7-Ply board:

41
Main features of corrugated
fiberboard containers/boxes
• Versatility
– Materials possessing a wide range of properties
– Flat sheets with a large range of structural and decorative properties
– Minimum space before erected
• High strength to weight characteristics
• Ready adaptation
– Suitable for a wide range of production techniques
• Production containment and protection features
– Contains and protects from producer to customer
• Low set up and tooling costs
– Many styles of boxes can be made by conventional converting equipment
• Low storage and handling costs
• Quick change characteristics
– Changes in style, graphics etc. can readily be made to suit changes in need
• Suitable for graphics design
– “smooth” easily printed surface (Washboarding is a problem.)
• Use of renewable resources and suitability for recycling
– made of wood fibers
• Contribution to the effectiveness of all handling and storage operations
• Smooth snag free surfaces
• Closely toleranced dimensions
• Secure closure method

42
Designing & STYLE OF BOXES
DESIGNING OF CFB BOXES
For designing the CFB boxes, one should know the following national & International Standards
on Corrugated Fiber Board Boxes & also the details of the factors which influence the
compression strength:
1. IS: 2771 Part (1) on ‘Corrugated fiberboard Boxes-Specifications’ is the core standard relevant
to design & manufacturing of corrugated boxes
2. Over all Requirements of Corrugated constructions as specified in alternative Rule 41& Item
222 (Singlewall Corrugated Boxes)
3. Factors affecting the compression strength
3. ASTM D4169: Safety Factors for Calculating Stacking loads
1. IS 2771 Part (1) on ‘Corrugated fiberboard Boxes-Specifications’ is the
core standard relevant to design & manufacturing of corrugated boxes.
(Indian Standards)
Board Product Weight in kg Perimeter(L+B+H) in
mm
BS in kg/cm²
Singlewall
(3-ply)
5 635 6
8 750 8
10 1025 9
Doublewall
(5-ply)
15 1275 10
20 1525 12
25 1575 13

43
Triplewall
(7-ply)
30 1650 14
40 1775 17
45 1900 24
75 2150 29
2. Over all Requirements of Corrugated constructions as specified in
alternative Rule 41& Item 222 (Singlewall Corrugated Boxes)
The American Association of Railroad (AAR) & the American Trucking Association (ATA)
collaborated with the corrugated fiberboard industry’s trade association (which eventually
became the Fiber Box Association) to institutionalize the use & standardize the properties of
corrugated fiberboard.
This alliance between carriers & the corrugated industry resulted in burst strength & ECT
becoming the standard way to specify corrugated fiberboard in United States today.
Max Wt.
Lbs(kg)
Max Perimeter
(L+B+H) in inch.(mm)
Min Wt of all
liners (GSM)
Min BS of Board
(kg/cm²)
Min ECT of
Board(KN/m)
20(9) 40(1016) 250 9 4.0
35(16) 50(1270) 320 10 4.6
50(22) 60(1524) 360 12 5.1
65(29) 75(1905) 410 14 5.6
80(36) 85(2159) 540 17 7.0
95(43) 95(2413) 670 19 7.7
120(54) 105(2667) 880 24 9.6

44
3. Factors affecting the Compression Strength
1. Relative humidity
2. Storage time
3. Stacking Pattern
4. Overhang or Wide deck spaces
1. Relative humidity
The most significant factor that weakens box walls is relative humidity. Humidity affects not
only the paper, but also the structure, since the board, joint & closures are usually bonded with
water- soluble adhesive.
High-humidity storage conditions can severely degrade the strength of a stack of boxes in
a matter of hours. At 85% RH, a box loses about 40% of its compression strength. At 90% RH,
the board’s moisture content is about 20% of its total weight & it even feels soft & damp to the
touch.
2. Storage time
A related factor is the time in the supply chain. The board weakens over time under load, &
with amount of transport and handling. A box under load loses about 40% of its strength in the
first 90 days of storage at TAPPI conditions i.e. at 65% RH and 27 ⁰C. Longer duration reduces
the strength to about 50%, but when coupled with high humidity (90% RH at 35 ⁰C for 6
months), the compression strength is reduced by 90%. Long-term storage, especially when
coupled with high humidity, can dramatically reduce stacking strength as shown in table below.
Effect of Relative Humidity and Time on load as percentage of initial CS at TAPPI conditions as
per Institute of Paper Science and Technology, from McKee & Whitsitt (1972)
90 days 180 days 360 days
50% RH 60% 55% 51%
65% RH 43% 40% 37%
75% RH 32% 29% 27%

45
80% RH 23% 21% 20%
85% RH 16% 15% 14%
90% RH 12% 11% 11%
3. Stacking Pattern
Third important factor is the stacking pattern on the pallet. Since the strength of a box is in is
walls & upright edges, perfectly aligned column-stacking best uses a box‘s compression
strength. Alignment of the edges & corners creates a support beam structure within a pallet
load.
If boxes are misaligned or an interlocking pattern is used, stacking strength will be lower.
While column stacking retains 85% of a box’s original compression strength, interlocking
reduces it to 50%. When boxes are interlocked, most of the supporting corners & edges rest on
the weakest part of the box below it. However, an interlocking pattern is often preferred for
the stability it lend to a load as it is handled & transported, especially if is not stretch-wrapped
or otherwise stabilized.
Columnar Stacking
4. Overhang & Wide deck spaces
Pallet overhang & wide deckboard gaps also reduces stacking strength, since they affect the
level surface of bottom-most boxes in the stack, which are expected to carry the heaviest load .
A 1-inch overhang can result in a 32% strength loss & wide deckboard spacing can strength by
as much as 15%.

46
4. ASTM D4169: Safety Factors for Calculating Stacking loads
ASTM D4169 has greatly simplified the effect of humidity, time, sacking pattern ect. Into a
factor called Safety factor or Environmental factor
CS = SL X F
Where, SL= Stacking load
CS= Compression strength
F =Safety/Environmental factor
And Stack load = weight of boxes on lower most box + weight of pallet, if used
1. ASTM D4169 recommends applying a higher set of factors when the contents don’t supports
the load i.e. items which are flexible or irregularly shaped may add none at all like flexible
pouches.
Whereas plastic bottles & folding cartons is considered as partially supported product
2. ASTM D4169 recommends applying a lower set of factors when the contents totally supports
the load i.e. items which are durable & can add considerable strength to overall such as metal
cans , glass bottles and appliances.
ASTM D4169: A higher set of Safety factors for unsupported product
Level Safety/Environmental
Factor
Conditions
Assurance Level 1 8 Worst storage condition
-Frequent high humidity(80%and above)
-Long-term storage(6-12 months)
-Interlocked
-Misaligned, overhang or wide deck space

47
Assurance Level 2 4.5 to 5 Average storage conditions
-Occasional high humidity (60-80%)
-Medium-term storage(3 months)
-Interlocked stacks
Assurance Level 3 3 Best storage conditions
-Humidity above 70%
-Storage: 6 weeks or less
-column stacks
ASTM D4169: A lower set of Safety factors for totally supported product
Level Safety/Environmental
Factor
Conditions
Assurance Level 1 3 Worst storage condition
-Frequent high humidity(80%and above)
-Long-term storage(6-12 months)
-Interlocked
-Misaligned, overhang or wide deck space
Assurance Level 2 2 Average storage conditions
-Occasional high humidity (60-80%)
-Medium-term storage(3 months)
-Interlocked stacks

48
How to specify BCT value?
Optimum Stack Height:
Example:
Considering the Product weight of pack is 15 Kgs.
So total stack load on lower most boxes is
=weight of 7 boxes + weight of pallet
= (15x7) + 25
= 130 kg
Now, since BCT =Stack Load x Safety Factor
Assurance Level 3 1.5 Best storage conditions
-Humidity above 70%
-Storage: 6 weeks or less
-column stacks

49
Hence BCT = 130 x 2 (considering the least SF)
BCT= 260 kg
STYLE OF BOXES
International Box Code: 01 - Commercial rolls and sheets
International Box Code: 02 - Slotted-type boxes
International Box Code: 03 - Telescope-type boxes
International Box Code: 04 - Folder-type boxes
International Box Code: 05 - Slide-type boxes
International Box Code: 06 - Rigid-type boxes
International Box Code: 07 - Ready-glued boxes
International Box Code: 09 - Interior fitments

50
Styles and the manufacturers joint:
The drawing style layouts as shown in this Code may need to be re-arranged depending on the
Manufacturers Joint chosen. Some styles may have manufacturer Joint which may be glued,
stitched or taped. A glued or stitched Joint may be an extension of either the short or the long
panel. The sketches show how these would be indicated on a drawing:
Example for all styles:
This applies to all designs in this Code.
Manual of Automated erection
Each design style includes one of the following indications
M - Usually manual erection
A - Usually automated erection
M/A - can be either manual or automated
M+A - requires a combination of both
These indications are based on current practice and are intended to give additional information
to specifiers and users. Some manually erected cases can be closed automatically (e.g.: 0216 or
0712)

51
International Box Code: 01 - Commercial rolls and sheets
Commercial rolls and sheets.
Description: 0100
Montage:
Description: 0110
Montage:
International Box Code: 02- Slotted-type boxes
• All flaps with same depth/height
• Only outer flaps center meeting
• Minimum waste-Thus highly efficient design but requires a gap plate

52
The most economical design
The most economical design is achieved when relative length, width, height ratio
is 2:1:2.
Regular Slotted Container – RSC - (International Box Code: 0201)
Full-Overlap Slotted Container – FOL - (International Box Code: 0203)

53
• All flaps with same depth/height
• Depth of all flaps = width of box
• Outer flaps overlap each other completely in closed condition
• Efficient in rough handling
• More stable bottom surface
• Used for selected products.
Lock-Bottom or Snap-bottom Box - (International Box Code : 0216)
• Top RSC with bottom die-cut having a portion to snap inside the provided
slot.
• Useful for smaller size or light weight product as bottom can not hold heavy
load.
• No plane surface at bottom

54
International Box Code: 03 - Telescope-type boxes
Full-Telescope Design-Style Box – FTD - (International Box Code: 0301)
Double-Cover Box – DC - (International Box Code: 0310)
Half-Slotted Box with Cover – HSC - (International Box Code: 0312)
Full-Telescope half-Slotted Box – FTHS - (International Box Code: 0320)
Normally Multiple piece boxes with separate top & bottom and the top overlap
the bottom at least 2/3

55
OTHER BOX CODES ARE-
International Box Code: 04 - Folder-type boxes
International Box Code: 05 - Slide-type boxes
International Box Code: 06 - Rigid-type boxes
International Box Code: 07 - Ready-glued boxes
International Box Code: 09 - Interior fitments
Liners, tubes, pads, build-ups, dividers, partitions and other inner pieces can be made in an
infinite variety of ways to separate or cushion products, to strengthen the box or to prevent
product movement by filling voids. This may be simple rectangles, or scored, slotted, scored
and slotted, or die cut shapes. Many of the common interior forms have been given
International Fibreboard Case Code numbers. The carrier classifications provide specifications
for some pieces used in the packing of glassware and other fragile articles.
0900 Pads
Pads are plain shapes of corrugated or solid fiberboard. They can be used to fill the space
between the inner flaps of an RSC, to completely cover the bottom or top of a box, or to
separate layers of product. Vertically, they can be used to separate products.
Tubes are scored rectangles, folded and sometimes joined with tape to form a multisided
structure open at both ends. When used as sleeves for individual items such as glassware,
adjacent shell provide double protection.

56
Partitions:
Partitions or divides provide a separate cell for each item in a box. They are used primarily for
glassware and other fragile articles.

57
QUALITY PARAMETERS & THEIR
ATTRIBUTES
1. Grammage
2. Thickness
3. Flute type
4. Bursting Strength
5. Ring crust test
6. Edge crust test
7. Flat crust test
8. Box compression strength
9. Moisture content
10.Cob Value
11.Solid content

58
GRAMMAGE & BASIS WEIGHT
Grammage (GSM) is mass of paper in grams for one square meter of paper i.e. g/m².
Or Grammage is a metric measure of paper weight based on the same square meter sheet of
paper, regardless of paper grade.
Basis Weight is also mass of paper but in pounds per 1,000 square feet
(abbreviated lb/MSF).
All the strength properties of paper are directly related to grammmage. Grammage has
its significance in strength, stiffness, opacity etc.
Another aspect of Grammage is cost factor. Grammage is directly proportional to cost
factor. Higher the grammage, higher will be the cost of paper.
THICKNESS OF CORRUGATED BOARD
Reduced board thickness (caliper) is an excellent indicator of reduced compression
strength; Caliper can be reduced by improper manufacture, excessive printing pressure,
improper handling and storage.
FLUTE TYPES
Flutes & their Charecteristics:
Characteristic A-Flute* B-Flute C-Flute E-Flute
Stack strength best* fair good poor
Printing poor good fair best
Die cutting poor good fair best
Puncture good fair best poor
Storage space most good fair least

59
Score/bend poor good fair best
Cushioning best fair good poor
Flat crush poor good fair fair
BURSTING STRENGTH
Bursting strength of a corrugated fiberboard is defined as the maximum hydraulic pressure
required to burst the paper when a controlled and constantly increasing pressure is applied
through a rubber diaphragm to a circular area.
Burst strength is the most useful as a measure of containment, for predicting internal resistance
to the kind of force that occurs when a box is dropped & the contents rupture the box wall (or
something from outside pushes in).
BURSTING STRENGTH OF THE 3- PLY BOARD= (BURST FACTOROF UPPER LINER X GSM OF
UPPER LINER) + 0.5(BURST FACTOR OF FLUTING MEDIUM X GSM OF FLUTING MEDIUM) +
(BURST FACTOR OF BOTTOM LINER X GSM OF BOTTOM LINER)

60
COMPRESSION TESTS
These are following test, which is used to estimate the compression resistance of Paper,
CFB boards & CFB Boxes.
FOR PAPERS RCT
FOR CFB BOARDS
VERTICAL(EDGEWISE) ECT
HORIZONTAL FCT
FOR CFB BOXES BCT
RING CRUST TEST (FOR PAPER)
Ring crush testing is used to measure the edgewise compression of paper and board
materials.
A short cylinder of material is inserted into an annular groove and axially loaded to
failure. Results are quoted in kN/m.
EDGE CRUST TEST (FOR CFB BOARD)
Edge Crush Test is carried out by applying the pressure on the edges of sample, at the
same time the applied force, which caused the crush of the material, is determined.
It is measured in kN/m; this value is proportional to the stacking strength. (Maximum
amount of packages, which are vertically placed on each other).

61
ECT= 1.28 x (RCT of liner-1 + (m x RCT of fluting medium) + RCT of liner-2)
Where,
m- Take up factor.
FLAT CRUST TEST
Similar to the edge compression test except the specimen is compressed in the flat.
Flat crush testing is a measure of the load bearing capability of corrugated board to loads
acting perpendicular to the fluting. The test provides a measure of flute rigidity.
Flat Crush Test is carried out by applying the pressure on the flat surface. Failure is
defined as the maximum load sustained before complete collapse. It is measured in kPa or
lb/in² (psi) or kg/cm².
The FCT test is generally used only for singlewall board. Doublewall measurements are
not meaningful because the middle liner shifts as the load is applied. A typical FCT for singlewall
C-flute is 20 psi.
Flat crush is another useful quality-control test in a corrugator plant. A high value
indicates good flute formation & a stiff medium. Low flat crush values can indicate weak
medium or flutes that are crushed, leanig or poorly formed. Too much roll or printing pressure
during manufacturing can reduce flat crush resistance. Board with a low FCT value is more
subjected to crushing in converting & printing equipments.

62
BOX COMRESSION TEST
The box compression test (BCT) measures the compressive strength of boxes made of
corrugated fiberboard. It provides a plot of deformation vs. compressive force.
• BCT is most important test to estimate the performance of the boxes. Compression
Strength is the “Dynamic” load applied on a compression Tester at the rate of 12.7 mm
per minute.
• Compression Strength is related to Stacking Strength but is actually quite different.
• Stacking strength is a key requirement of most transport package.
What is Box Compression Strength?

63
• Top to Bottom Loading.
• Load applied at constant rate until box collapses.
• C.S is the maximum load attained at or before critical deflection is reached
• The ability to carry a top load is affected by
• The structure of the container.
• The environment it encounters.
• The ability of the inner (primary) package.
• The dividers and corner post, etc.
• To sustain the load.
Factors affecting the load distribution……….
• The factors that have a bearing on the manner in which loads are distributed on a
corrugated box are:-
– Box Geometry
– Allocation and position of the material from which the box is made.

64
The compression strength is a function of
– Box perimeter (2L + 2W)
– Edgewise compression strength of the board.
– Flexural stiffness of the board.
McKee Formula:
BCT = K x ECT x Square root of (Z x T)
• K - is Constant having Value 0.599.
• BCT - is Compression strength (Kgs).
• ECT - is Edgewise Crush test value (kN/m).
• Z = (2*L+2*W) is Perimeter of box (mm).
• T - is Thickness of board (mm).
MOISTURE CONTENT
Moisture content is amount of water present in the paper/board. It is generally
expressed in %.
The amount of water contained in paper expressed as a percentage of the paper's total weight.
The primary constituents of paper, fibers of cellulose, have a strong affinity for water, and will
gain (or lose) it readily, depending on the amount of moisture in the air, or the relative
humidity of the surrounding environment. This hygroscopic characteristic of paper makes it
dimensionally unstable, as the length and/or width of a paper can change depending on how
much water the paper has gained or lost.
The moisture content of paper also affects its various mechanical, surface, and electrical
properties, and contributes to the qualities of printability and runnability in the various printing
processes. Generally, a range of 5% to 7% is average for the moisture content present in paper
stock.
There are a variety of ways to determine a paper's moisture content.

65
One method is the "oven-drying method," in which a sample is weighed, placed in an oven at
105-107⁰C for an hour, and weighed again. The difference in weight divided by the original
weight times one hundred is the percent moisture of the paper.
Quick determinations of moisture content made during papermaking are accomplished with
infrared or microwave sensors. Results from these sensors can be used to alter the moisture
content of the paper if necessary. A moisture meter, containing sensors that use measures of
electrical resistance or electrical holding power, can also be used to gauge moisture content of
paper.
COBB- VALUE
It is the amount of water absorbed by the paper when it is brought into contact with water
for specified period of time.
Higher Cobb- Value indicates, paper is more susceptible to absorb the water & vice-versa.
If the paper is not sufficiently water resistant, it will absorb water and may affect the
printing adversely. Moreover it will also tend to open the joint by dissolving the adhesive used.
This test is done on either side of the paper. Thus, the rate at which linerboard will absorb
water can affect the quality of corrugators bonding, manufacturer’s joints, and the glueability
of boxes on packaging lines.
To improve cobb-value of paper, during paper making ‘Sizing’ is done (water repellent /
resistant materials added or fibers are chemically treated to reduce affinity.)
For reasonable protection 150-180 gm/m² Cobb. For severe exposures 80-100 gm/m².
SOLID CONTENT
Solid content is specifies as amount of soluble active solids material formerly known as ‘Gum
Powder’. More the solid content in liquid gum more will be the strength of bond. So if you
want a high strength box simply use high solid content adhesive.
A starch adhesive should have minimum 21 % of solid content (Active solid matter). Higher solid
Content gives more tack; lower solid content gives low tack. In order to achieve high strength
bond, 28-32% solid content is sufficient but this value may vary in specific circumstances.

66
DEFECTS IN CORRUGATED
FIBREBOARD BOXES
VARIOUS ASPECTS OF CORRUGATION BOARD DEFECTS:
Defects in corrugated boxes are a result of combination of various aspects such as:
1. Adhesives: Adhesives, Solids, Viscosity, Tackiness
2. Paper: Cobb-value, Calendaring Surface uniformity, Sizing, Moisture content, Absorption
capacity of paper
3. Machine: Corrugating Roll alignments, Pressure gum line registration, Gum intake, heating of
rolls and hot plates, Speed of machine, Pressure
4. Processing
5. Tuning
6. Manual
General Defects in corrugated boards:
• De-lamination
• Wash-boarding
• Blisters on corrugated board
• Cockles-wrinkles
• Warping
• Delay in Drying or Setting time
• Foaming

67
De-lamination of Corrugated Board
Reasons Remedies
• Inadequate solid content: Less solid
means less adhesive thus giving lesser
strength bond
• Improper Viscosity: Too low or too high
viscosity
• Poor tack: Poor tack could lead to de-
lamination while processing
• Insufficient Adhesive
• Solid-Active water soluble gum powder should be
more than 16% preferably 20 to 25% considering the
type of paper to be used. Low solid cannot give
tackiness and thickness of film which can hold two
papers together
• If viscosity is too low then whole of adhesive will soak
into the paper and there will be no film between two
papers to hold them together and if viscosity is too high
then it will not allow the gum to go inner matrix of the
paper thus there is no formation of adhesive film
• One must ensure that adhesive is applied uniformly
over the flutes
Wash-boarding
It is appearance of wet marks on the liner along flute edges across the liner.
Reasons Remedies
• Use of excess adhesives
• Very thin liner medium
• Improper Viscosity
• High alkaline adhesive
• Excess moisture in liner
• Adjust the viscosity
• Check the pH of adhesive before the application
(should not be greater than 9)
• Adjust doctor roll
• Tune machine speed and pressure
• Increase wrap of liner on pre-heat
Blisters on corrugated board
Appearance of bubble like loose, unbounded, uneven areas over the liner.
Reasons Remedies
• Use of highly alkaline adhesives
• Spotty gum application at fingers
• Uneven moisture in paper
• Check adhesive pH
• Adjust the fingers
• Use pre-heater

68
Cockles-wrinkles
Appearance of wrinkles in the liner between flute tips
Reasons Remedies
• Excess adhesive application • Reduce the adhesive by tuning
Delay in Drying
Reasons Remedies
• Excess water in glue (low solids)
• High viscosity
• Moisture content in paper
• Atmosphere humidity
• Solids to water ratio should be at least 1:4
• Viscosity should be 25 to 30
• Use pre-heater
N.B. - Sometimes operator assumes that low viscosity gum has low tack hence he releases
excess gum. This excess gum on paper increases drying time. When there is higher moisture
in the air and paper, gum should have low viscosity and higher solids.
Foaming
Due to foaming in liquid gum there is uneven spreading of adhesive, which could cause
bubbling, de-lamination, shabby floor, wastage etc.
Reasons Remedies
• It’s a result of bacterial growth
• Paper and starch have affinity of
moisture, which causes bacterial
growth
• Other machine related problems
• Insist gum manufacturers to use biocides
• Regular cleaning of water storage tanks and gum
vessel. We suggest formaldehyde (2%) for cleaning of
storage tanks
Warping
It’s a bending of corrugated board after complete drying
Reasons Remedies
• Could be the difference in moisture
percentage in liner and single or
double facer
• Use high solid content gum
• Increase the wrapping of liner on pre-heater

69
COMMON CONVERTING DEFECTS
S.
No.
Defect/
Problem
Cause Remedy
01 Panel overlap - Box panel too long
- Box not folding
correctly
- Cut box down t size or operator must
manipulate box to get correct gap.
- Operator must manipulate box to get
better fold. Printer-slotter must score
deep enough without excessive pull
roll or slotter head pressure to get
good fold
02 Blocking of
finished glue
lap boxes
- Excess adhesive
- Excessive pressure
on conveyer belt
- Improper adhesive
viscosity
- Improper timing of
glue roll or extrusion
head
- Adjust feed gauges
- Reduce pressure on conveyer belt
- Correct for smooth flow
- Re- adjust glue roll or extrusion head
03 Fish-tailing or
box- crooked
- Improper alignment
of scores and or
slots on folder-
gluers
- Uneven feed or pull-
roll pressure
- Blank folded
improperly
- Check and adjust scores and/or
slotting heads on folder- gluer
- Adjust for correct pressure
- Check and adjust folding arms or belts
04 Failure at
glue-lap joint
- Weak surface fiber
bond
Use liner with adequate surface fiber bond.
05 Glue- lap not
adhered to
board after
press section
- Poor penetration of
glue
- Insufficient glue
- Warped board
- Insufficient
compression time
- Adjust speed of machine. Change
adhesive
- Adjust adhesive applicator roll
- Increase hold down pressure
- Increase compression time or use
faster setting adhesive
06 Trim adhered
to glue-lap
- Dull knives or
slotting heads
- Trim removal
system blocked on
folder- gluer
- Check, resharpen or replace knives or
heads
- Check and clean system

70
07 Weak glue-
lap bond
- Insufficient glue
application
- Poor glue
penetration
- Too short a
compression time
- Glue setting up
either too slow or
fast
- Check board for glue pattern and
enough glue in reservoir
- Check glue viscosity, tack and setup
time
- Either lengthen compression or slow
down
- Change adhesive
08 Board
crushed after
die cutting
- Inadequate
clearance for
rubber; also, light
gsm or dried out
paper
- Reduce height of rubber and/ or
width. Humidify board if possible. Use
lower durometer rubber
09 Slotted cuts
or leading
edge trim ”
hange” on
die
- Nicking in die to
retain paper
attachment is
burred
- Bend or crushed
rule
- Remove burr at nicking point of die
- Re- rule.

71
Common printing defects
Sr.
No.
Defect/
Problem
Cause Remedy
01 Improper
intensity and
amount of
printing ink
applied to a sheet
- Unevenly adjusted
form roller causing
uneven ink
distribution across
press
- Fountain keys
improperly adjusted
causing excessive or
light ink application.
- Washboard stock
- Adjust form rollers for even
pressure across rollers
- For optimum conditions,
increase ink flow by adjusting
fountain keys until minimum
amount is being used that will
provide good coverage
- Decrease print cylinder
clearance
02 Poor legibility or
clarity of outline
of printed matter
- Printing plates not
uniform in thickness
- Excessive print
pressure
- Excessive pressure
between form rollers
and printing plate
- Excessive ink
application
- Dirty printing plate
- Replace defective printing plate
- Use only enough print cylinder
clearance between rollers and
printing plate
- Increase clearance between
form rollers and printing plate
- Reduce ink application
- Clean printing plate
03 Dirty printing - Dry and dusty board
- Ragged slitter edge
- Get board with better surface
finish
- Adjust or sharpen slitter knives
04 Ink-fill in - Ink viscosity too high
- Insufficient metering
of ink film on anilox
roll
- Reduce viscosity
- Check with machinery
manufacturer for
recommended material or
practice.
05 Distorted image - Too much printing
pressure
- Reduce pressure
06 Halo on edge of
plate
- Too much anilox roll
pressure
- Reduce pressure
07 Poor (light) ink
coverage
- Ink viscosity too low
- Printing plate surface
glazed
- Improper printing
plate hardness
- add stronger fresh ink
- Clean or replace plate
- Check with plate maker for
proper hardness
08 First colour down - First down (solid - Reduce viscosity of first down

72
(solid) bleeding
though second
colour down
(new)
colour) not dry colour. Run press slower
09 Ink coverage void - Low spot in printing
plate
- Use makeready to elevate low
spot
10 Smearing - Ink does not dry
properly
- Board not very
absorbent
- Anilox roll has cells
which are too large
- Consult ink supplier
- Print using an ink with a lower
viscosity, or add and additive to
the ink to improve its
penetration into the board
- Consult the supplier.

73
Testing on corrugated
fiberboard boxes
1. Burst Strength test
Definition:
Bursting strength of a corrugated fiberboard is defined as the maximum hydraulic pressure
required to burst the paper when a controlled and constantly increasing pressure is applied
through a rubber diaphragm to a circular area.
Introduction:
The oldest & most common corrugated board test is the Mullen burst strength test.
Bursting strength is related primarily to the tensile strength of the liners, & is sometimes
preferred as a quality control test by paper mills because it is simple & quick.
Bursting Strength Tester

74
Test Methods:
TAPPI T810: Bursting strength of corrugated & solid fiberboard
ISO 2759: Board- determination of bursting strength
Conditioning:
27± 3⁰C & 65% Relative Humidity
Procedure:
1. With a sharp razor blade slitter test pieces are from the board.
2. The sizes of the test piece shall be at least 100mmx 100mm.
3. The test piece is fixed in a bursting strength tester. The lower platen has a rubber
membrane stretched across the opening which expands until it is bursts a hole through
the sample.
4. In this way the load is applied & the pressure requires for bursting of paper/ board is
read from the pressure gauge. It is measured in kg/cm² or psi (lbs/in.²).
Precaution:
The test is subjected to error if the instrument, diaphragm, & gauges are not properly
maintained or if the procedures are not strictly followed. The measurement is sensitive to
clamping pressure. When the pressure is too low, sample will slip & higher readings will result.
When it is too high, the flutes will be crushed, resulting in low reading.
Controversy about this test:
Historically bursting strength was considered to be an important indicator of shipping container
adequacy, but this is a matter of debate. Also it does not necessarily simulate a generalizable
form of package damage, & does not reflect a package’s overall strength.
Burst strength is the most useful as a measure of containment, for predicting internal resistance
to the kind of force that occurs when a box is dropped & the contents rupture the box wall (or
something from outside pushes in).

75
2. Ring Crust Test (RCT)
Ring crush testing is used to measure the edgewise compression of paper and board materials.
A short cylinder of material is inserted into an annular groove and axially loaded to failure.
Results are quoted in kN/m.
Principle & Equipment for Ring Crush Test
Test Methods:
TAPPI T822: Ring crush of paperboard (rigid support method)
Conditioning:
Procedure:
1. A test strip with a width of 12.7 mm (1/2inch) is cut with a sharp blade from a paper
sample previously cut in the machine direction to the length of 152.4 mm (6 inches).Its
edges have to be straight, clean & parallel.

76
2. The test strip is placed in a circular slot forming a ring. It is essentially a metal block
containing an annular groove, 6.35mm ± 0.25 mm deep & with an outer diameter of
49.30 mm ± 0.05 mm. The centre island is exchangeable & a series of center islands
with different diameters allow the slot to accommodate different thickness of the
paper.
3. The holder with a test strip is placed between the platens of the crush tester.
4. These platens are moved together at a speed of 10±3 mm/min as per Indian Standard &
12.5±2.5 mm/min as per ASTM Standard & the loading registered on a recorder.
Thickness of test piece in mm Diameter of disc in mm (Tolerance ± 0.05 mm)
0.15 -0.17 48.80
0.17-0.20 48.70
0.20-0.23 48.60
0.23-0.28 48.50
0.28-0.32 48.30
0.32-0.37 48.20
0.37-0.42 48.00
0.42-0.49 47.80
Precaution:
The test is prone to errors if the samples are not cut or prepare properly. If the edges are
not straight and parallel, the RCT value will be reduced. Samples should be cut with a
precision sample cutter or some other method that will cut perfectly clean, parallel &
perpendicular edges.

77
3. Edge Crust Test (ECT)
Introduction:
Edge Crush Test is carried out by applying the pressure on the edges of sample, at the same
time the applied force, which caused the crush of the material, is determined. It is measured in
kN/m; this value is proportional to the stacking strength. (Maximum amount of packages,
which are vertically placed on each other)
The ECT is the best material test to predict a box’s stacking strength. This is the reason that, the
U.S. transports carriers & the fiberboard industry agreed to accept the ECT as an alternative to
the Mullen Burst test for the standard way to differentiate corrugated board grade.
ECT measures the columnar strength of the board & also called as short-column test. It
measures the amount of the force require to crush the piece of board standing on its edge with
its flute vertical.
Principle & Equipment for Edge Crush Test
Test Method:
TAPPI T811: Edgewise compressive strength of corrugated fiberboard (short column test).
ISO 3037: Corrugated fiberboard- Determination of edgewise crush resistance
Conditioning:

78
Procedure:
1. Samples are cut 2 inches long and the load bearing edges must be cut squarely with
precise, straight parallel edges. The hight depends on the flute type: 1.25 inches for B-
flute, 1.5 inches for C-flute, & 2 inches for A-flute, doublewall & triplewall.
Sample Dimensions
Flute type Length in inches (mm) Height in inches (mm)
A or Doublewall or
Triplewall
2(51) 2(51)
B 2(51) 1.25(32)
C 2(51) 1.50(38)
2. The corrugation runs in short (height) direction.
3. The long edges i.e. loading edges are dipped into molten paraffin wax (approximate
melting point, 52⁰C to a depth of ¼ inch (6mm) & held until the absorbed paraffin, to
stiffen & prevent the edges from crinkling or rolling over.
4. Normally, a 3 second dip in molten paraffin at a temperature 69- 74 ⁰C is satisfactory. If
excessively rapid migration is encountered, reduce the temperature of the molten
paraffin. This forces the failure to occur in the body of the board (the column of the
flutes) rather than edges.
5. The test strip is placed vertically between the platens of crush tester.
6. These platens are moved together at a speed of 10±3 mm/min as per Indian Standard &
12.7±2.5 mm/min as per ASTM Standard & the loading registered on a recorder.
Specimen for Edge Crust Test

79
Precaution:
The test is prone to errors if the samples are not cut or prepare properly. If the flutes are
crushed when cutting or the edges are not straight and parallel, the ECT value will be
reduced. Samples should be cut with a precision sample cutter or some other method that
will cut perfectly clean, parallel & perpendicular edges.
4. Flat crush testing (FCT)
Introduction:
Flat Crush Test is carried out by applying the pressure on the flat surface. Failure is defined as
the maximum load sustained before complete collapse. It is measured in kPa or lb/in² (psi) or
kg/cm². Board with a low FCT value is more subjected to crushing in converting & printing
equipments.
Flat crush testing is a measure of the load bearing capability of corrugated board to loads acting
perpendicular to the fluting.
Principle & Equipment for Flat Crush Test
Test Methods:
TAPPI T825: Flat crush test of corrugated board (Flexible beam method)
ISO 3035: Single faced & singlewall corrugated fiberboard- Determination of Flat-crush
resistance

80
Conditioning:
Procedure:
1. Round test piece are cut from the corrugated board.
2. The test piece shall have a surface area of 10 square inch (64.5 cm²) in accordance with
FEFCO- Standard & 5 square inch (32.25 cm²) in accordance with TAPPI-Standard
3. The test piece is placed between the platens of crush tester. The platen should move
together at a speed of 10±3 mm/min as per Indian Standard & 12.5 ±2.5 as per ASTM
Standard & loading is registered on a recorder.
Conclusion:
The FCT test is generally used only for singlewall board. Doublewall measurements are not
meaningful because the middle liner shifts as the load is applied. A typical FCT for singlewall C-
flute is 20 psi.
Flat crush is another useful quality-control test in a corrugator plant. A high value indicates
good flute formation & a stiff medium. Low flat crush values can indicate weak medium or
flutes that are crused, leanig or poorly formed. Too much roll or printing pressure during
manufacturing can reduce flat crush resistance
5. Puncture Test
Introduction:
The puncture test is a more violent form of the burst test. The puncture test measures a
board’s resistance to penetration by sharp & solid objects, such as the corner of a pallet. It is
commonly uses in place of the Mullen burst test for heavier grade of corrugated board, like
triple wall (7-Ply), because of the Mullen diaphragms will not pop through the thicker boards.
It uses a Beach test Apparatus with swinging pendulum that has a special pyramid shaped
puncture point that breaks through the corrugated board. Weight is added to the pendulum
until it is sufficient to puncture the board. The apparatus used has a scale that gives the
puncture reading.

81
Puncture Tester
The results are given by the test apparatus in Beach units (named for the inventor of the test),
& reported to three significant figures. Beach units can be converted to joules, a measure of
mechanical energy, using the following;
1 Beach unit ₌ 0.0299 joules ₌ 0.305kg-cm
Test Method:
TAPPI T803: Puncture test of containerboard
ISO 3036: Determination of puncture resistance
Conditioning:
Procedure:
1. With a razor blade slitter, the test pieces are cut from the board in a size of minimum
175mmx 175mm.
2. The test piece is clamped between the plates & they are pressed against each other
with the handle.

82
3. The pendulum is freed & the pointed head penetrates the test piece. The energy
consumed for the penetration is indicated by the pointer & noted. The pendulum can be
loaded with different weights & for each weight there is corresponding scale.
Precaution:
The test is subjected to errors if the puncture point is damaged or if the apparatus is not level.
Another way to use the apparatus is to keep the weight constant & simply release the
pendulum from increasing heights until a failure height is identified (force = weight x height),
although this is not the standard method.
Comparison of puncture test & bursting strength test:
Although the puncture test is used for specifying triplewall board in same that the Mullen test
for single or doublewall board, the two tests are not the same & do not yield comparable units
(Mullen results are reported in psi or kg/cm²).
Both tests stress the board in similar way, by a force perpendicular to the surface. However,
they differ in two significant ways
First, Puncture test uses a concentrated point stress, while the Mullen uses a stress distributed
over an area. Second, the puncture test uses a rapid loading, While in the Mullen test, the load
increases slowly.
The result is affected most by the tensile & tears strength of the board’s linerboards & the
stiffness of the combined board. The puncture test results for singlewall board can be as low as
100 Beach units (3 joules) & triple wall board ranges from 700 to 1,300 or more Beach units.
6. Box Compression Test
Test Methods:
ASTM D642: Standard Test Method for Determining Compressive Resistance of Shipping
Containers, Components, & Unit Loads
Scope:
1. This method covers compression tests on shipping containers (for ex ample, boxes &
drums) or components or both. Shipping containers may be tested with or without
contents. The procedure may be used for measuring the ability of the container to resist
external compressive loads applied to its faces, to diagonally opposite edges, or to

83
corners. This test method covers testing of multiple containers or unit loads, in addition
to individual shipping containers, components, materials, or combination thereof.
2. The test method of applying load may be used to compare the characteristics of a given
design of container with a standard, or to compare the characteristic of container
differing in construction.
3. This method is related to TAPPI T 804, which is similar for fixed platen machines but
does not recognize swivel platen machines. This test method fulfills the requirements of
International Organization for Standardization (ISO) Test Methods 2874 & 2872. The ISO
standards may not meet the requirements for this test method.
Reference Documents:
ASTM D 4577: Test Method for Compression Resistance of a Container Under Constant Loads
TAPPI T804: Compression testing of fiberboard shipping containers
ISO 2872: Packaging – Complete, filled transport packages- Compression test
ISO 2874: Packaging – Complete, filled transport packages- Stacking test using compression
tester.

84
Apparatus:
Compression testing machine (Swivel- Platen Testing Machine):
Swivel platen testing machine- a testing machine equipped with two platens, one is rigidly
restrained from while the other platen is universally mounted & allow to tilts freely.
Two platens, flat to within 0.01 inch (0.25mm) for each 12 inch (304.8 mm) in length & one
which is moveable in the vertical direction so as to compress the specimen between the
platens. One is the load measuring platen, and both should be of sufficient size so that the test
container does not extend beyond the edges of the platens. One platen is fixed in the horizontal
direction so as to have no lateral movement greater than 0.05 in (1.3 mm). The second platen is
attached to the machine by a swivel or universal joint directly centered on the platen, thus
allowing the platen to tilt freely.
Significance & Uses:
1. Compressive resistance is one of the properties use to evaluate the ability of shipping
containers, components & unit loads to successfully survive the compressive forces
which are subjected to during storage & distribution.
2. Compressive resistance may be determined with swivel –platen- type testing machines.
Also unit load are generally tested in top-to-bottom orientation.
Conditioning:
Procedure:
1. Center the specimen on the bottom platen of the testing machine so as not to incur
eccentric loading.
2. Significant errors may result during testing, if the specimen is placed off-center on the
platen. Also, estensive damage to equipment may occur if test specimens are putted
off-center on the platen.
3. Bring the platens into contact with the specimen by applying initial pressure or pre-load.
4. For single-wall (3-Ply) corrugated container, an intitial pressure or pre-load of 50lbf
(222N) on the specimen is recommended. For Double-wall (5-Ply) & triple-wall (7-Ply)

85
boxes the pre-loads of 100lbf (445N) & 500lbf (2220N) respectively are recommended.
For other type of test specimens a suitable pre-load may or may not be selected.
5. If the testing machine is not fitted with a deformation recorder, record the test load for
every 0.1 inch or2.5 mm of deformation of the container. See the load deformation
recorder to display zero deformation.
6. When testing full containers and the load sensing device is located under the bottom
platen, ensure that the test machine is adjusted to zero.
7. Apply the load with a continuous motion of the movable platen of the testing machine
at a speed of 0.5 ± 0.01 in (12.7 ± 2.5 mm)/ min until failure or a specified load has been
reached.(As per IS speed should 10±3mm/min)
8. Prior to testing for each type of loading, critical points shall be established, where
applicable. Record the compressive load at these critical deformations, together with
the maximum load and deformation.
Result:-
Box compression of given corrugated box is kg (lbs) at mm (in) deflection.
7. GRAMMAGE OF CFB BOARD
Definition:
Grammage or basis weight is mass of a unit area of paper and expressed in terms of grams per
square metre. Grammage has its significance in strength, stiffness, opacity etc.
Another aspect of Grammage is cost factor. Grammage is directly proportional to cost
factor. Higher the grammage, higher will be the cost of paper.

86
Procedure:
 Use a specimen or cut a test piece in the form of a rectangular to only convenient size of
not less than 10cm x 10 cm.
 Measure the sides correct to 0.5% for each dimensions.
 Determine the area of specimen the test piece correct to the nearest 0.25% of the area.
 Weigh the specimen/ test piece correct to 3 significant figure. Use a template of this
accuracy is permitted.
Working Formula:
Weight (gm) Weight (gm)
GSM = Or GSM = x 100
Area (m²) Area (1 m²)
The maximum, minimum and average is calculated and in expressed in gm/ m².

87
8. WATER ABSORBANCY (COBB VALUE) OF PAPER
Definition:
This test indicates the amount of water absorbed by the paper when it is brought into contact
with water for specified period of time. It is also known as the Cobb- value of paper.
Introduction:
If the paper is not sufficiently water resistant, it will absorb water and may affect the printing
adversely. Moreover it will also tend to open the joint by dissolving the adhesive used. This test
is done on either side of the paper. Thus, the rate at which linerboard will absorb water can
affect the quality of corrugators bonding, manufacturer’s joints, and the glueability of boxes on
packaging lines. Sizing may also affect the printability of linerboards with water-based
flexographic inks. While adhesive and ink formulations can be modified to suit high, moderate,
or low levels of substrate sizing, problems generally arise when the range of linerboards used
varies widely in sizing characteristics.
There is confusion between moisture content & Cobb value of paper. Both are
completely different thing. Moisture content is the amount of water contained in the paper
inherently. It is expressed as %. While Cobb value is the amount of water absorbed by paper for
a particular duration of time.
In normal conditions, it stabilizes at around 7% in the reels of paper. A 10% variation in the
relative humidity of the ambient air leads to a 1% variation in the moisture content of the paper
leading to a difference in length of the paper of approx. 0.1% in the Cross Direction.
SIGNIFICANCE & USES:
1) Paper constitutes 80-85% cellulose, 8-10% hemicellulose, carbohydrates, and 8-10% lignin all
being hydrophilic.
2) First 3-4% moisture absorbed is inseparable hydrogen-bond. Even in absence environmental
vapors / external water source, this level is achieved by dry cellulose by picking up water
from drying agent during paper making (ph.pentoxide).
3) To improve cobb-value of paper, during paper making ‘Sizing’ is done (water repellent /
resistant materials added or fibres are chemically treated to reduce affinity.
4) Ash contents in paper reveals presence of fillers and hence indicates cobb-value.

88
5) Paper prone to quick absorbtion is difficult to dry & difficult to wet is easy to dry.
6) For reasonable protection 150-180 gm/m2 cobb. For severe exposures 80-100 gm/m2.
Procedure:
 Sample is placed on the rubber plate of the cob tester and wet it.
 The test piece is placed on rubber sheet in such a way that the surface to be tested
should be faced uppermost.
 The ring is fixed, clamped so that there is no leakage.
 Then clamp it firmly so that there should be no leakage.
 Then pour the water up to 1cm height and start the stop watch
 After 45 seconds, pour off the water.
 Unclamp the cylinder, allow draining surplus water and pressing tightly with blotting
paper.
 After this, weight the sample immediately as there is chance of evaporation of water
which would fluctuate the result.
COB TESTER
Note- This test method is as per ISO but per TAPPI 441, the time duration is 2 minutes for paper
and 30 minutes for board.

89
Working Formula:
One minute Cobb test reflects amount of water absorbed by 1 square meter of exposed
surface in 1 minute, hence the formula is
(Final weight – Initial weight)
% Weight Gain = x 100
(Initial weight)
The unit of Cobb value is GSM i.e. gm/m².
9. Determination of Flute Type
Objective: To determine the flute type
Significance:
Different flute type has their different properties as listed below:
Characteristic A-Flute* B-Flute C-Flute E-Flute
Stack strength best* fair good poor
Printing poor good fair best
Die cutting poor good fair best
Puncture good fair best poor
Storage space most good fair least
Score/bend poor good fair best
Cushioning best fair good poor

90
Flat crush poor good fair fair
Test Methods:
I. S.: 2771 - 1977 (I) - To identify the flute type
Procedure:
1. Cut the board into 10mmX10mm.
2. Cunt the number of flutes.
Result:
Tested corrugated board has Flute.
FLUTE PROFILE FLUTES PER 10 cm
A - BROAD 10.5-12.5
C- MEDIUM 12.5-14.7
B- NARROW 15.3-18.1
E- MICRO 28.5-33.4

91
FUTURE TRENDES
RCT PAPER Vs BURST GRADE PAPER
There are two grades of corrugated liners.
These are the RCT and burst grade paper.
Differences in the manufacture of the two grades:
Basic paper making principals and equipment are the same regardless of mill location. Both
types of paper can be made with the same raw material on the same equipment. To do
this, process and machine adjustments are made to differentiate the two grades.
RCT PAPER
The fibers used for ring crush paper are refined to a higher degree than those used of basis
weight paper. These fibers are ‘frizzed’ in much the same way we tend to get split ends in our
hair. These frizzed parts of the fiber allow the fibers to better interlock with one another when
the fibers are laid out on the Fourdrinier Table. These frizzed parts of the fiber also have an
opportunity to align themselves in the cross machine orientation of the produced paper.
Secondly, the Wire mesh on the Fourdrinier Table is slowed to almost match the velocity of the
stock being put out from the head boxes. This helps the fibers maintain their random
orientation on the wire mesh thus permitting more fibers to align in the cross machine
direction.
Lastly, ring crush grade paper receives additional calendaring and finishing

92
Burst Grade Paper
In contrast to this, Basis weight or Burst Grade paper is ‘pulled’ onto the Fourdrinier table with
the wire mesh traveling at a much higher velocity than the fibers causing them to align in the
machine direction (perpendicular to a container’s top to bottom compression).

93
GLOSSORY
Adhesive- Material capable of adhering one surface to another.
Bale- A shaped unit, usually containing compressible materials.
Basis Weight-Weight of linerboard or corrugating medium expressed in terms of pounds per
1,000 square feet (MSF).
Board-Component used in the manufacture of corrugated.
Box-A container that completely encloses it contents.
Boxboard-A general term designating the material used in the manufacture of corrugated..
Box Maker-A establishment that has the equipment and the capabilities to manufacture
corrugated containers.
Built-Up-Term describing inner packing that has multiple layers glued together for maximum
protection.
Bulk-Loose items not packed or bound within a container.
Bundle-Two or more items fastened together suitable for shipping.
Bursting Strength-The ability of material in pounds per square inch, as measured by the Cady of
Mullen tester, to withstand burst through.
Cardboard-A thin material used for signs, shoeboxes etc.
Carton-A folding box made from boxboard, used for shipping and warehousing.
Case-A filled container, or could be used to describe a bulk pack.
Chipboard-A thin paperboard usually made for display, or small size containers and partitions.
Container-A item used to contain or hold goods for shipping or warehousing.
Corrugated Medium- Corrugating material that has been formed into flutes and glued to faces
of linerboard.
Corrugators- The machine that is used to produce, manufacture and corrugate fibreboard.

94
Die Cut-A style of packaging that is stamped out using steel rule cutting dies, and is usually
perimeter stripped. Die cut containers are especially useful for displays.
Dimensions-As used in describing the inside or outside size of a sheet or container generally
stated as length, width, and depth in that sequence.
ECT-Known as edge crush test, this is the standard for testing the linerboard’s ability for
stacking performance.
Facings-Also called liners which are the outer sheeting which is glued to the center flute.
Fibreboard Box-A box made from corrugated material.
Flaps-The part of the shipping container that is folding on top and bottom creased by scores.
Flaps are then usually closed with tape, glue or metal staples.
Flute- The material in the center of a corrugated sheet that resembles a waved sheet of paper.
Fluting is expressed in letter form: A, B, C, E, F, and B/C.
Flute Direction-Direction of fluting material usually in the vertical direction. Fluting direction is
usually determined by how the container will be stacked.
Glue-The material used to adhere one side of the linerboard to the other.
Inner Packing-Items used inside the container to support, and protect the item, or items that
the container contains.
Joint- The part of the container that is used to form a four sided box. The joint is usually in the
form of glue, tape of wire stitch.
Kraft, Fourdrinier-Containerboard, made from kraft pulp on a fourdrinier machine.
Label- A sheet of paper that is applied to the surface of a corrugated sheet. Labels are usually
described in terms of full labels which are usually the full size of the corrugated sheet, or spot
labels which are usually smaller.
Laminator-A machine that adheres two or more sheets to a piece of fibreboard.
Master Pack-A shipper designed to contain a number of inner containers
Pad-A corrugated sheet used as a separator, or used in the container as extra protection.
Panel-A side of a container.

95
Partitions-Corrugated or chipboard sheets that are slotted to form cells when assembled.
Printer-Slotter-A machine that takes a flat corrugated sheet, prints, scores and slots the sheet
to form a box when joined.
Sheet-A square or rectangular piece of corrugated.
Shipping Container-A container that is used in conjunction with commercial shipping.
Slip Sheet-A sheet that is used as a base on which other material is transported or shipped.
Slit-A cut used in the corrugated in place of a score.
Slot-A cutout in the manufacture of a corrugated container usually on top and bottom, which is
used to form the flaps of the container.
Stitches-Metal staples used in the sealing of the joint of a container.
Tape-A strip of paper sometimes reinforced with material used to form the joint of the
container. Can be used also for closure of the top and bottom flaps of the container. Common
sizes of tape are 2" and 3" widths.
Taper- The machine that applies the tape joint to a container.
Tube- A multisided form that has no top or bottom sides usually used as a form of inner
packing.

96
Bibliography
 Corrugated Box Handbook by P. V. Narayanan.
 Technical Association of Pulp and Paper Industry.
 European Federation of Corrugated Box Manufacturers.
 Bureau of Indian Standards.
 Institute of Packaging Professionals.
 Fibre Box Association.
 The Wiley Encyclopedia of Packaging Technology.
 Fundamentals of Packaging Technology
 International Organization for Standardization (ISO).

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