Finishing methods

Finishing Finishing Methods

WOODFINISHING
Surface Preparation

The first step to a good finish is to make sure the surface the finish will be applied
to is free of all defects such as dents, gouges, scratches and milling marks. Most
finishes bring out the natural grain and beauty of the wood. Unfortunately, they
may also magnify any defects that may have gone unnoticed. What appears to
be a minor defect on raw wood will stand out like a sore thumb when a stain or
finish is applied.

Common Sense.

Surface preparation should begin before the project is assembled. A fair amount
of common sense should be used during construction. For example: any surface
that can't be easily reached after assembly should be sanded before assembly.
In general attention to detail such as tight joint lines and excess glue squeeze out
should be addressed during construction. Excess stain will accumulate between
poorly fitted joints and will appear as unsightly dark lines when the finish has
been applied. The glue squeeze out should be left to dry and then removed by
using a scraper. During construction I am constantly asking myself, "How will this
affect the surface when I apply a stain or finish"? Ask yourself this while you
work.

Mill Marks

If you wish to build a quality piece of furniture, I recommend buying good quality
lumber, free of knots, sap, blemishes etc. If you do so, about the only defect you
will have to deal with on the board will be mill marks. When boards are run
through a planer, the rotating planer knives take shallow bites out of the wood.
Mill marks appear as a series of repeating raised bumps that run across the grain
of the board. If the knives are very dull, the marks really stand out, but more often
they are less pronounced, in some cases invisible to the naked eye. It's important
to note that mill marks are present on every board that has been run through a
planer, regardless of quality or source.

Sometimes mill marks are very hard to see. If you don't detect and remove them,
they will really stand out once a stain or finish has been applied. The best way to
sight mill marks or any other minor flaws or defects is to use reflected light.
Position a lamp above the work surface at about a 30 degree angle to the
surface. You will be surprised when the marks you could not see before now look
like mountain peaks and valleys. Overall, the best way to remove mill marks and
other minor defects like small surface scratches is by sanding.

zaini@selectvest.com Wisdom Management Services (M) Sdn. Bhd. 1


Sanding

Choosing The Right Paper

There are several types of sandpaper, some are designed for sanding finishes
like lacquer and varnish while others are best for sanding raw wood. Garnet
Paper is an orange colored sandpaper that is made of a natural abrasive. It is
excellent for sanding raw wood. Another type of paper that is favored by furniture
and cabinet makers for sanding raw wood is Aluminum Oxide paper
(sometimes known as production paper). This is the standard brownish colored
paper found in most hardware and paint stores. Aluminum Oxide is a man made
abrasive and will last a little longer than Garnet paper. Either of the two will
produce excellent results. The types of paper you want to stay away from for
sanding raw wood are the Silicon Carbide (Wet or Dry) paper which is black in
color, and the light gray colored papers which are lubricated and used to sand
lacquers and other topcoats.

Grits.

Sandpaper is graded by using a number system. The finer the paper, the higher
the number. Garnet and Alum. Oxide paper range in grit sizes from 36 (Very
Corse) to 240 (Fine).

Choosing A Sander

Over the past few years a variety of sanders have been introduced onto the
woodworking market. Some work very well, while others, not so well. The three
most common sanders used for surface prep are a belt sander, orbital sander
(pad sander) and the most recent random orbital sander. Each sander produces
a distinct surface finish. A belt sander is best used when a lot of material has to
be removed from the surface. For example when glued up boards have to be
leveled. It is a dangerous tool, make one mistake and you may wind up ruining
the workpiece. Even though a belt sander removes stock quickly, I don't think it's
worth the risk. The belt sander leaves straight lined scratch pattern.

While orbital sanders do not remove stock like belt sanders, some of the
heavier models like the Porter Cable Model 330 Speed Bloc will do a great job of
removing scratches and milling marks when a piece of 80 grit sandpaper is
mounted to it. These sanders leave small orbital scratch patterns that are nearly
invisible to the naked eye. When using an orbital sander, don't press down too
hard on the worksurface. Let the weight of the machine do the job. Although you
can initially sand across grain make sure you take your last passes with the grain
to avoid leaving scratch marks on the stock. The random orbital sander is the
machine I most often use. Because it creates an orbital as well as revolving
motion, it removes stock much quicker than a pad sander and at the same time
leaves a scratch pattern that is almost swirl free, even when sanding across



grain. To properly use this sander, start it while it is on the wood. If you wait until
it is running at full speed before you set it on the work, it may gouge out the
surface.

Sanding Sequence

Many woodworkers believe that if you sand the work to a super fine grit, you will
achieve a better finish. This is not true. The only purpose for sanding is to
remove mill marks, tool marks, other defects and to smooth the surface. When
sanding, sandpaper leaves small grooves relative to the grit size of the paper you
are using. By sanding with progressively finer grits you are making these grooves
smaller. Once the grooves are small enough so they can't be seen with the
naked eye, you do not need to go any further. While it is not necessary to
progressively sand using every available grit, you should not skip too many grit
sizes. Use a grit that is just small enough to remove the grooves left by the
previous paper. I usually use 100 grit to remove milling marks and any other
surface defects, then move to 180 to refine the grooves and finish up with 240
grit. If mill marks are very pronounced, I will start with 80 grit, then use 120 and
finish with 220. Sanding up to 220 or 240 on most woods will make the grooves
small enough so they are naked to the invisible eye. However, there are some
species of wood that may require sanding to a finer grit before the grooves are
not visible.

SAFETY NOTE! PLEASE WEAR A RESPIRATOR OR FILTER MASK WHILE
PERFORMING ANY SANDING OPERATION.

Sanding should proceed as follows:

1. Remove mill marks and other surface defects using 80 or 100 grit paper.

2. Once mill marks are removed, move up to a medium grit paper (120 or 180
grit). This will refine the scratch pattern. To see if you have removed all of the
deeper grooves left by the previous grit paper, first blow off the sawdust then
mount a lamp above the worksurface (at about a 30 degree angle). The reflecting
light will show any deeper grooves that may have been left. Continue to sand
until all the deeper grooves are removed.



3. Continue on using 220 or 240 grit. On most woods the scratches left by 220 or
240 grit paper will be small enough as not to be seen by the naked eye. If you
can still see scratches under reflected light, move up to a finer grit usually 280
grit.

Sanding Method

Regardless of the type of sanding machine you use, there are some basic rules
to follow. Many texts and articles tell the reader never to sand against the grain.
This is not always true. When you first start to sand using coarse paper it may be
necessary to remove a lot of material because you have to remove mill marks
and level the surface. Initially sanding against the grain will remove stock much
quicker. Once mill marks are removed and the surface has been leveled, finish
up by sanding with the grain before moving up to a finer grit. Also there are some
cases where you are forced to sand against the grain. One such case is at a joint
line where two pieces of wood meet at an angle. In this case it is also o.k. to
sand against the two pieces, just make sure you finish by sanding with the grain
up to the joint line.

Removing excess glue squeeze out.

As mentioned previously, you should use a good amount of common sense
during the construction process. Removing excess glue squeeze out is a perfect
example of this. Many woodworkers have a number of theories about how and
when to remove glue squeeze out. One theory I do not agree with is to remove
the glue while it is still wet by using a damp cloth. By doing this, you are forcing
the glue down into the pores. Furthermore, if you use a damp cloth, you are
thinning the glue out thus it will penetrate even deeper into the pores of the
wood. This method also makes it difficult to determine if all of the glue has been
removed. If the glue has not been totally removed in some areas, it will act as a
sealer and prevent a stain or finish from penetrating into the wood.

When the stain or finish is applied, the area in question will appear light and
blotchy. Another method that works much better is to let the glue set up before
removing it. As white or yellow glue dries, it first starts to skin over and form a
blister. If you don't wait long enough before removing the glue, the skin will break
open and deposit wet glue onto the work surface. If you wait about 45 minutes to
1 hour, the glue should be dry enough to remove easily with a paint or glue
scraper. There is a way to test the glue in order to determine if it has setup to the



point where it should be removed. Take a pin and prick one of the globs of glue,
if the blister breaks and fresh glue comes out it is not yet ready to be removed.
Wait a while longer. If the glue is left to dry hard it could be difficult to remove,
however not impossible. I would still recommend using this method over the
method of removing the glue with a damp cloth while still wet. A good paint
scraper is the best tool for glue removal. The scraper should have a solid blade
and sharp edge. It should also have a large heavy handle.

Some Final Tips!

Removing Sawdust. Use a tack cloth to remove sawdust from the worksurface.
Lightly wipe the surface, don't rub hard or press down or the resin in the tack
cloth will be deposited on the worksurface and may contaminate it. Start the
finishing process immediately after the surface has been prepared.
Humidity in a shop can start to raise the grain and if you handle the workpiece
too much after it has been sanded, the natural oils in your hands may also
contaminate the workpiece. Hinges, pulls and other hardware. Drill all
mounting holes for hinges, pulls and other hardware before you sand and then
mount the hardware to test the fit and location. Once satisfied remove all
hardware before you start to sand. Do not remount the hardware until the whole
finishing process is complete.



Furniture repair

As an introduction, a few words about the author of this column. While I now do
furniture repair and refinishing only as a hobby and for a "sideline" income, I
worked at it full-time for a number of years, both in furniture stores that had their
own shops, as well as establishments whose sole business was to repair and
refinish furniture. I make no claim to being an authority on furniture periods or
styles, but I do know a little about furniture work, which I’ll try to pass on in these
columns. I have learned over the years there’s a lot of mystery associated with
furniture repair and refinishing (probably promoted by those in the business!) that
needn’t be. Hopefully, some of the "tips and tricks" you read here will bolster your
enthusiasm for what can be a very rewarding and productive hobby. If you have
any specific questions, address them to me at the Enterprise, with a self-
addressed, stamped envelope, and I will answer. If your question has enough
general appeal, I’ll use it in this column.

Unless your home has recently been entirely refurnished, you’ve probably got at
least one piece that has a "watermark" that ugly white blotch left from water
standing on the surface too long before it was wiped up. It may be just a few
dots, or a ring left by a glass or planter. If the mark is white there’s good news
(Black watermarks are another problem we’ll deal with later).

To fix 1 piece of furniture, or 15, you’ll have to spend about $10.00. You’ll need
0000 (called four oh) steel wool; Turtle Wax polish and Scratch remover for cars
(This product has a very fine abrasive mixed in with the wax which will let you get
a super shine.); some clean rags, and some oil. Whatever oil you cook with will
work, Puritan, Wesson, etc. makes no difference.

Pour about 1 teaspoon of oil directly on the watermark. It should fade
considerably and may disappear. Don’t be deceived, it’s still there. Rub the mark
gently with the steel wool, moving with the grain of the wood, not across. After a
minute of this procedure, wipe it clean to see how much of the mark you have
removed. Repeat this procedure, using as little pressure as necessary to scratch
the surface, until the mark is gone. Apply the Turtle Wax according to the
directions on the can. This will remove the abrasion marks left by the steel wool
You’ll have to do the entire surface in order to get a uniform sheen, so be ready
for some work when you start to remove that mark on the dining room table!

On a large piece, there’s a lot of "elbow grease" involved, but not a lot of
expense. There are other products that will work as well as Turtle Wax, but that’s
the one I use. Just be sure it’s not a polishing or rubbing compound. Those
products have an abrasive grit that’s much too rough for furniture finish work.

A little background: 99% of factory made furniture is finished with lacquer, which
will absorb standing water, and in some cases of constant high humidity, directly
from the air! The white marks are caused by water that has become trapped in



the finish. The procedure described above simply removes the very top layer of
finish, getting rid of the water(mark).

Furniture stripper

The primary requirement for furniture work is patience. Nowhere is this
characteristic needed more than in stripping furniture. Let’s see if we can make
this messy task any easier.

First, what do you need? Specific items will vary from piece to piece, but the
following list should get you through most jobs. You’ll need stripper, of course.
What kind? You basically have two options, and then two choices within each
option. Here are the options. If you’re really keen on the environment, you’ll want
a water-base stripper. They work fine, and as the label suggests, you can wash
the residue off with water. The downside is that using a water based stripper
means you must. sand the piece completely before you do anything else. A
solvent based stripper doesn’t raise the grain of the wood, but you have to be
more careful with it. Sanding is kept to a minimum. Whether you choose water or
solvent base, your next choice is going to be liquid or semi-paste. Liquid usually
strips faster, but the semi-paste is excellent for adhering to vertical surfaces and
carved material to remove the old finish from all the cracks and crevices.

Other items you’ll need include a flexible blade drywall knife, 3", with a dull edge
and slightly rounded corners. No, you can’t buy it that way, except for the 3" and
flexible part. Dull the edge and round the corners slightly with a file. This will help
prevent gouging the wood when you scrape off the old finish. Steel wool, both XX
and 00 grades, to help remove what the putty knife doesn’t get, as well as to
work on carvings and legs. Industrial grade rubber gloves. The kind sold for
washing dishes won’t last - don’t bother. When I worked where cotton rags were
plentiful and cheap, that’s what I used. Now I use paper towels, and buy them in
the 12 pack when they’re on special. If you’re using a solvent base stripper, you’ll
also need some lacquer thinner - a quart will be plenty. Get a natural bristle
brush, not synthetic, preferably the cheapest one you can find, 2" wide, for
applying the stripper. Lots of old newspapers to cover the floor under and around
the area you’re working in and a quart of paint thinner. If you buy a length of 1/4"
or 5/16" dowel rod and cut it into 5-6" lengths and then run both ends through a
pencil sharpener, you’ll have some great tools for digging in cracks and crevices
that won’t chew up the wood. Some disposable foil pans for pouring the stripper
into and catching the mess as it comes off will also be handy.

Now what? A well-ventilated, well lit and well ventilated area to work in; old
clothes that you can afford to throw away if necessary; and patience. Every
stripper I’ve seen says put it on (in such-and-such manner) and let it stand for at
least 15 minutes...and nobody does. Read the directions and follow them. The



people that made the stuff know more about it than you do. They put directions
on the can so you’ll get good results and use their product again, instead of
something else. If you don’t have a watch, borrow one. Time yourself when
applying stripper. It will save you a lot of work and frustration in the future.

By the way, the paint thinner is used to clean the piece before you do anything
else. Stripper won’t cut through grease, oil, or wax. Paint thinner will remove
them all. The lacquer thinner is used as a final wash (with solvent strippers) after
you’ve finished stripping. It will remove the last traces of stripper (so it won’t
attack the new finish) and will neutralize any left in the cracks and crevices.


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