|
| |
|
Saving the Finish
© Copyright 2000 by Jeff Jewitt
Not reproducible in any form, written or electronic, without permission
Sooner
or later, every woodworker is faced with the prospect of refinishing an old
piece of furniture. Whether it's a treasured "find" at a flea market or
auction, or a favor for a relative or friend, etc., most people consider
stripping off the old finish and refinishing the only option of successfully
restoring the appearance of the piece.
Although I am a professional finisher, stripping
furniture is the most thankless task in our shop. Despite the fact that we
have proper application and exhaust equipment for handling the chemicals
used, the process is messy and time consuming.
For do-it-your-selfers, or woodworkers with limited shop space, the
process is now a littler easier with the advent of "safer" strippers, but
nonetheless, I don't know anyone who relishes the idea of spending a weekend
with a couple gallons of stripper and a paint scraper.
When many woodworkers see an old dirty
finish, their first thought is to remove it.
In some cases this is the best approach as I will explain below.
However, most old finishes do not need to be completely removed to
restore the appearance of old furniture.
Much of the patina on old pieces is on the outer surface of the wood
under the finish and is the result of exposure to sun and air.
The chemicals in most strippers "pull out" some of this patina which
can affect the desirable characteristics of an old piece. Strippers can also
affect the glue in joints and loosen veneer.
Museums and conservators of antique and historically important
furniture rarely remove a finish and will only do so when the finish has
degraded to the point that the stability of the piece is jeopardized. Most
of the time, the finish is partially removed which involves the removal of
the damaged surface layer only. Almost all techniques involve some type of
cleaning and removal of accumulations
of dirt, oils, and old polishes from years of use.
Since many of the pieces that come into my shop
are antiques, most of the work that we do centers on saving the original
finish. While some techniques call for specialized solvents and chemicals,
there are several techniques for cleaning and restoring an old finish to the
point where the piece once again looks good. My background and research in
conservation has taught me several cleaning and conservation techniques that
can be used by most woodworkers to restore a piece of furniture without
stripping the finish. In this article, I'll detail several of these
techniques that can be done by most woodworkers with a minimum of
specialized materials. Before we start, I'd like to discuss those finishes
which shouldn't be saved.
FINISHES THAT CAN'T BE SAVED
Not all old finishes can be saved. Finishes that
are severely damaged or degraded to the point where they can no longer
effectively do a good job of protecting the wood should be removed. Although
most conservators would like to save the original finish when possible,
finishes that have degraded to the point where the wood is in jeopardy
should be removed. These situations include severe water or heat damage,
large losses of the finish where the wood is exposed and situations where
the finish is severely discolored. Another finish that cannot be saved is a
finish that is sticky. Sticky finishes are those that have become chemically
altered to the point where they will never fully harden, and finishes
applied over them shortly become soft and sticky. Severe water or heat
damage appear as large white areas where the finish is peeling or flaking
off. Large exposed areas of
wood are very difficult to blend in without highly developed skills so
removal of the entire finish is called for. Another problem finish is one in
which the finish has been mixed with pigment and applied thickly. Old
varnishes and shellacs applied in this manner may develop large cracks or
"islands" which show the bare wood below. This finish should be removed in
most cases. An exception are crazed or cracked finishes where the cracks do
not go all the way through to the wood below. I'll explain how to deal with
this later.
The goal in restoring an old finish is not to
make it look brand new. At best, this treatment should restore as much of
the original condition as possible and prevent further deterioration. While
by no means is restoring a finish a "quick-fix" type of repair, on most
pieces it should be less time-consuming and expensive than a complete
stripping and refinishing. In addition, you do not run the risk of ruining
the value of an old piece of furniture by removing a piece of its history.
The following are the steps in saving an old finish. Sealing damage,
cleaning, abrading the old finish (if necessary) and finally waxing.
SEALING DAMAGE
Damage that needs to be sealed are dents,
scratches and small areas of finish that have been worn away. The cleaning
process involves water and solvents that could possibly affect bare wood and
it should be protected. For sealing, I use a 2 lb. cut
light-colored shellac.
Using a red-sable artist's brush, I brush several light coats of shellac to
the damaged area and then let the shellac dry overnight. Do not try to match
the color to the surrounding finish at this point. The cleaning will lighten
up the color so blending in at this point will result in a mismatch.
CLEANING
Before cleaning, it helps to know what the
finish is so that the appropriate cleaners can be used. I test the finish by
a three step process using various solvents. Find an inconspicuous spot such
as behind a leg and dab a little
denatured ethyl alcohol on the finish with
a small brush or cotton swab. After thirty seconds tap the area with your
finger - if it's sticky the finish is shellac. If the alcohol doesn't affect
the finish try a little lacquer thinner. If the finish still isn't sticky,
it is probably an oil-based varnish or polyurethane. Knowing which finish
you have minimizes possible damage from cleaning solvents as we will see
later.
Cleaning is a two step process which removes
both water-soluble and oil-soluble dirt and grime. The first cleaning step
uses a hydrocarbon based cleaner like mineral spirits or VM&P Naphtha. I
prefer to use VM&P Naphtha rather than mineral spirits because it flashes or
evaporates much quicker. It's important to test a small amount of the
cleaner on an inconspicuous area. Certain oil-based finishes varnishes can
irreversibly whiten on exposure to some hydrocarbons so testing is crucial
and it's important to know what the finish is. Oil finishes may soften and
be completely removed, but in most cases VM&P Naphtha has proved the best
all-around solvent in my use. Dampen a clean cloth with the Naphtha and rub
a small surface at a time. Do not saturate the surface. Switch to clean
cloths frequently.
The next step involves using a detergent mixed
with distilled water. Professionals use a wide variety of specialized
products, but I've found an alternative is Dawn®
- a commercial dish-washing detergent that is readily available. I use a
solution of one capful in a pint of lukewarm water. Apply the solution with
a dampened clean cloth, (not dripping wet) and rub a small area at a time.
Some grime comes off quickly, while others may take a little longer. You'll
see your progress by the dirt on the rag, so change the surface frequently.
Afterwards, wipe all the excess detergent off with clean water and proceed
to the next step.
ABRADING
The cleaning above removes the surface dirt from
the finish but it still may be hazy or whitish. Part of this problem may be
from small crazing or cracks in the finish which reflect light - making the
surface appear dull. If this is the case and the cracks do not go all the
way through to the wood, abrading part of the finish will remove most of the
cracks. I use non-loading sandpaper like
3M's Fre-cut®Gold,
(sandpaper manufactured to minimize clogging), to abrade away a portion of
the finish. I start with 240 grit and proceed to 320 grit and finally 400
grit. I back the paper with a felt or cork block and avoid the edges since
it's easy to cut completely through the finish. I strongly recommend wearing
a dust mask since the dust is irritating. Sand in straight lines with the
finish and wipe the residue off frequently with a Naphtha dampened rag. You
can stop sanding when the grain of the wood is visible or when the cracks
have disappeared. Patience is required because a heavy hand will cut through
the finish and you'll have no choice but to strip at that point. Wipe the
piece with Naphtha and let dry overnight.
At this point you have the option of
applying more finish, which may be necessary to restore luster and depth, or
to blend in and protect repairs. Pigments or dyes mixed with shellac can be
used to touch up and light areas and applied with a small brush. Afterwards,
several coats of shellac can be brushed or padded on. You don't have to
apply any finish though, and it's recommended that you don't if you're
unsure of whether this will detract from the value of the piece.
WAXING
The piece is now ready for the final step. I
prefer to wax and buff out, but if you want, you can apply a light coat of
whatever finish you prefer. Shellac or varnish will both work over most
finishes but shellac should be used if the piece is an antique. I would
avoid polyurethane because it will not bond very well to an old finish.
Either way, you may need to do a little touch-up first. There may be small
areas where the finish is removed down to the bare wood. These should be
sealed with several coats of a 2 lb. cut shellac applied with an artist's
brush or a small varnish brush. After drying these, areas can be blended
into the surrounding area using shellac mixed with dry artists pigments.
After drying, seal all repaired areas again with a 2 lb. cut shellac.
For the final waxing, I prefer a good quality
furniture wax like
Antiquax. All these waxes come in clear and brown. I prefer the
colored waxes because any wax that lodges in crevices or small defects will
not be noticeable when dry. Put a scoop of wax inside a clean cloth and
apply the wax in a small circular motion. On turned areas, carvings and
other irregular areas, work the wax in with a stiff bristle brush. Work on a
manageable area at a time and when the wax hazes buff it out using a clean
cloth. After drying overnight, give it a second waxing.
When the second coat dries you'll have a
restored finish without the bother or hassle of stripping. You'll find it's much less work and the result is that you
haven't possibly detracted from the value if the piece is an antique. As an
added bonus, you find that the entire process can be done in one weekend,
rather than two or three weekends. And finally, the piece will have retained
the patina that took so long to acquire with time.
Related Products
BACK TO TOP |
© Copyright 2001-2004 Homestead Finishing
Products
|
