1. Soil Classifications
There are 3 main classifications of soils:
1. Type of Soil
2. Solubility Characteristics of Soil
3. Types of Cleaning Compounds
These classes are helpful about understanding cleaning processes. They are parts of one unit.
1. Type of Soil
1.1 Inorganic Soil
Matter that was never "alive", and thus contain no carbon.
a) Hard-water deposits such as water spots, calcium and magnesium carbonates (Scale and
lime deposits )
b) Metallic deposits such as rust, corrosion, and oxidation.
c) Alkaline deposits such as films left by improper rinsing after use of an alkaline cleaner.
d) Minerals and rock formation. ( Sand, silt, clay )
Oftentimes acidic cleaners are used to remove inorganic deposits. Minerals are often cleaned
with general purpose cleaners.
1.2 Organic Soil
Matter that once “lived” and that does contain carbon.
a) Fat & Grease ( Body oils and animal fat )
b) Carbonhydrates & Proteins ( sugar, honey, chocolate, jelly, chicken, milk, beef, … etc.)
c) Living matter ( mold, yeast, bacteria)
Most of the time organic soils are best removed using alkaline cleaners or solvents.
1.3 Petroleum Soils
Motor oils, axle greases, wax, gums and other products made from petroleum. These soils
contain no water - in fact they repel water - and thus do not have a pH. They often require
another petroleum based solvent to remove them.
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2. 1.4 Combination Soils
These are soils that contain an organic plus an inorganic soil and/or a petroleum substances.
These soils are difficult to remove because they are hard to identify. Proper identification is
critical. Most combination soils are removed with a very concentrated, highly built
combination type cleaners - alkalines and solvents or acids and solvents.
It is important to select the appropriate solvent and the correct cleaning compound for
removing a specific soil. An acid-cleaning compound is most appropriate for the removal of
inorganic deposits. An alkaline cleaner is more effective in removing organic deposits. If
these classes are subdivided, it is easier to determine the specific characteristics of each type
of soil and the most effective cleaning compound. Table 1–1 gives a breakdown of soil
subclasses
Table 1-1 Classification of Soil Deposits
Type of Soil Soil Subclass
Hard-water deposits
Inorganic soil Metallic deposits
Alkaline deposits
Food deposits
Organic soil Petroleum deposits
Nonpetroleum deposits
2. Solubility Characteristics of Soil
2.1 Water-soluble Soils
These soils will dissolve in tap water and in other solvents that do not contain a cleaning
compound. They include many inorganic salts, sugars, starches, and minerals. Soils of this
type present no technical problem because their removal is merely a dissolving action. The
greater part of food soil can either by suspended in water or can simply be removed from a
surface by the force of a water spray. Any soils not directly soluble in water will be left
behind as a thin film or as a deposit.
2.2 Acid-soluble Soils
Acid-soluble soils are soluble in acidic solutions with a pH below 7.0. Deposits include films
of oxidized iron (rust), zinc carbonates (ZnCO3), calcium oxalates [Ca(COO)2], metal oxides
(iron and zinc) on stainless steel, waterstone (reaction between various alkaline cleaners and
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3. chemical constituents of water having noncarbonate hardness), hard-water scale [Calcium
carbonates (CaCO3) & Magnesium carbonates (MgCO3) ], and milkstone (a waterstone and
milk film interaction, precipitated by heat on a metal surface).
2.3 Alkali-soluble Soils
Alkali-soluble soils are basic media with a pH above 7.0. Fatty acids, blood, proteins, and
other organic deposits are solubilized by an alkaline solution.
2.4 Insoluble Soils
Soils insoluble in the cleaning solution are insoluble throughout the range of normal cleaning
solutions. However, they must be loosened from the surface on which they are attached and
subsequently suspended in the cleaning media.
Table 1-2 Solubility Characteristics of Food Soils
Surface Deposit Solubility
Sugar Water-soluble
Fat Alkali-soluble
Protein Alkali-soluble
Starch Water & Alkali Soluble
Monovalent Salts Water & Acid Soluble
Polyvalent Salts Acid Soluble
3. Types of Cleaning Compounds
Soil deposits are characteristically complex in nature and are frequently complicated by
organic soils being protected by deposits of inorganic soils, and vice versa. Therefore, it is
important to identify correctly the type of deposit and to use the most effective cleaning
compound or combination of compounds to effectively remove soil deposits. It is frequently
essential to utilize a two-step cleaning procedure that contains more than one Cleaning
compound to remove a combination of inorganic and organic deposits. Table 1–3 illustrates
the types of cleaning compounds applicable to the broad categories of soil.
Table 1-3 Types of Cleaning Compounds for Soil Deposits
Type of Soil Required Cleaning
Compound
Inorganic soil Acid-type cleaner
Organic soil
Nonpetroleum Alkaline-type
cleaner
Petroleum Solvent-type
cleaner
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4. Cleaning Process
The major functions of a cleaning compound are to lower the surface tension of water so that
soils may be dislodged and loosened and to suspend soil particles for subsequent flushing
away. To complete the cleaning process, a sanitizer is applied to destroy residual
microorganisms that are exposed through cleaning.
Cleaning process has three sub-processes.
1. Seperation of the soil from the surface
Soil separation can occur through mechanical actions; through alteration of the chemical
nature of soil; or without alteration of the chemical nature of the soil.
The soil and surface must be thoroughly wet for a cleaning compound to aid in separating the
soil from the surface. The cleaning compound reduces the energy binding the soil to a surface,
permitting the soil to be loosened and separated.
2. Soil dispersion in the cleaning solution
Dispersion is the dilution of soil in a cleaning solution. Soil that is soluble in a cleaning
solution is dispersed if an adequate dilution of cleaning medium is maintained and if the
solubility limits of the soil in the media are not exceeded. The use of fresh cleaning solution
or the continuous dilution of the dispersed solution with fresh solution will increase
dispersion.
Some soils that have been loosened from the surface being cleaned will not dissolve in the
cleaning media. Dispersion of insoluble soils is more complicated. It is important to reduce
soil to smaller particles or droplets with transport away from the cleaned surface.
A synergistic action of the energy reduction activity of the cleaning compound and the
mechanical energy can break the soil into small particles and separate it from the surface.
3. Prevention of redeposition of dispersed soil.
Redeposition can be reduced by removal of the dispersed solution from the surface being
cleaned. Other reduction methods are continued agitation of the dispersed solution while still
in association with the surface to stop settling of the dispersed soil; prevention of any reaction
of the cleaning compound with water on the soil; elimination of any residual solution and
dispersed soil that may have collected on the surface by flushing or rinsing the cleaned
surface; and maintenance of soil in a finely dispersed condition to avoid further entrapment on
the cleaned surface.
Adsorption of surface-active agents on the surface of soil particles causes similar electrical
charges to be imparted to the particles. This condition prevents aggregation of larger particles
because like-charged particles repel each other. Surface redeposition is minimized because a
similar repulsion exists between surfactant-coated particles and the surfactant-coated clean
surface.
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5. The best “rule of thumb” to consider when selecting a cleaning compound is that “like
cleans like.” Therefore, an acid soil requires an acid cleaner, and an alkaline soil should be
removed with an alkaline cleaning compound.
Factors Affecting Cleaning Performance
Time: contact time on the surface being cleaned
Action: physical force exerted onto the surface (velocity or flow)
Concentration: amount of cleaner used
Temperature: amount of energy (as heat) used in the cleaning solution
Water: used to prepare cleaning solution
Individual: worker performing clean-up operation
Nature: composition of the soil
Surface: what material is being cleaned
These factors spell out the acronym TACT WINS and describe important factors involved in
cleaning.
Energy Equation For Cleaning
There’s actually an equation that determines the total amount of energy it takes to properly
clean something:
There are three types of energy that combine to create a clean surface. Mechanical energy
comes from you, scrubbing away. It is
Mechanical Energy external forces. While scrubing with
sponge , you exert on soil to leave it on
Thermal Energy Total Energy surfaces. Thermal energy comes from the
(Cleaning) temperature of the cleaning solution. At the
Chemical Energy
optimum cleaning solution temperature
alkali or acidic cleaning solutions are more
effective. Their solubility and chemical activity increase. Chemical energy is what the
chemicals in cleaning products bring to the equation. Mechanical and thermal energy vary
with chemical energy.
Detergents’ cleaning formulas provide chemical energy through :
• Wetting of the surface and soil
• Emulsification of oils
• Saponification, or creating water soluble soaps with basic or alkaline compounds
• Softening of water to neutralize the negative effects of calcium and magnesium
• Adding enzymes and/or bleach to attack stains
• Cleaning with solvents in combination with or in place of water
These factors are often used together to maximize effects.
There are 3 parameters that gets the dirty surface 100% clean which keeping the balance with
each other. For example if you don’t want to scrub very hard, but still want the same Total
Energy (cleaning), you need to raise either the Thermal energy or the Chemical energy.
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