Finishing Oily Woods
by Sal Marino
Traditionally, some of the world’s most colorful
woods like rosewood, teak, ebony and cocobolo are often used to build
musical instruments, decorative boxes, jewelry, accents and trim on
furniture. Recently though, many of these woods are being used to build
whole pieces or sets of custom furniture. As more are being used by not
only professional but amateur woodworkers, many people are running into
difficulty when it comes to finishing these woods.
The main problem lies in the natural oils and resins that are contained
within woods like rosewood, teak cocobolo, etc. The oils create two main
1. When oil based finishes like varnish, polyurethane, danish oil
and others are applied over the wood, the finish sometimes
takes a very long time to dry. All of these types of oil based finishes
dry by absorbing oxygen. The natural oils and resins contained in exotic
woods will slow down the drying time by retarding the absorption of
oxygen into the finish. Sometimes, if you happen to get stuck with a
very oily piece of wood, the finish may stay tacky for weeks.
2. Adhesion. While other finishes like nitrocellulose lacquers,
pre-catalyzed lacquers and water based finishes dry better over oily
woods, the oils may prevent these finishes from adhering properly to the
Below, I have included a few different types
of finishes and finishing techniques that I have had success with, but
first, before applying any finish, you must perform the following steps
to remove any oils that may be on the surface of the wood.
Preparing the Surface
1. After preparing the wood by usual methods of sanding, clean all
sawdust off the surface.
2. Using a rag lightly dampened with a quick evaporating solvent like
acetone, lacquer thinner or denatured alcohol, wipe the whole surface
down. This gets all the natural oils off the surface of the wood, but
you must work quickly to apply your first coat of finish, for if you
don’t, more natural oils will bleed onto the surface.
While many exotic woods are rarely stained,
because the natural color of the wood is so appealing, all need
some type of finish applied to protect against abrasion, moisture, dirt,
dust and sunlight. Over the years, I have had the opportunity to try
many finishes and finishing techniques over oily woods, and I have had
the most success with the following:
1. Shellac Sealer / Natural Resin Varnish Finish.
If you are going to be finishing a piece of furniture that is going to
get a lot of use, (like a table) you'll want to use some type of
topcoat finish that will protect it against abrasion as well as spills,
dirt and dust along with making it easy to maintain. This finish has
worked well for me.
After wiping down the surface with quick evaporating
solvent, (acetone, lacquer thinner) apply two thin coats of shellac. I
use 3 lb. cut clear shellac and reduce it 50/50 with denatured alcohol.
Apply the two coats by either spraying or brushing with high quality
natural or china bristle brush. Let first coat dry about 2 hours before
applying second coat. This will seal the surface and prevent any more
natural oils in the wood from bleeding back to the top. Let these two
coats dry at least 2 days. Next, lightly scuff sand the shellac with 400 grit
paper. And wipe the dust off surface.
The next step is to apply 2 to three coats of a
natural resin varnish. DO NOT USE A POLYURETHANE OR ANY VARNISH THAT HAS
POLYURETHANE IN IT. IT MAY NOT ADHERE TO SHELLAC. I use a varnish
manufactured by H Behlen & Bro. This is called Rock Hard Table
Top Varnish. It is a natural resin varnish that contains no poly. Reduce
each coat approx. 20 percent with Behlen’s Rock Hard Reducer. This works
out to 4 parts varnish and 1 part reducer. I use a foam brush to apply
this varnish, but if you are used to using a bristle brush and get good
results, stick with it. Let each coat dry at least 24 hours (longer if
you are in a humid area). Scuff sand very lightly with 320 grit paper
between coats. After the last coat is applied, if the sheen does not
look even, you may apply a few additional coats until you achieve a
uniform sheen. This is a gloss varnish, if you wish to obtain a
semi-gloss or satin finish, simply wait about a week for the finish to
cure and then rub out with 600 grit paper and rubbing oil or use 0000
steel wool or synthetic non-woven
abrasive pads. If you go with the synthetic pads, purchase the fine type. The light
gray color is usually equivalent to 000 or 0000 steel wool. If desired,
you may also apply a coat of high quality paste wax after rubbing.
2. Shellac / Wax Finish
On furniture or wooden objects that don’t need maximum protection such
as a wall clock, dresser or just trim, I have often just used a few
coats of shellac and the applied a coat of paste wax over it. After
wiping down the surface with quick evaporating solvent, (acetone,
lacquer thinner) apply four thin coats of shellac using the same mixture
and process as described in the previous process. Let the four coats of
shellac dry at least 3 days, then sand lightly first with 320 grit paper
to remove any dust nibs and smooth out any brush marks. After sanding
with 320, use 600 grit to smooth the surface and leave a mellow sheen.
Wipe off dust and apply a coat of high quality paste wax such as Briwax
or Minwax Paste Wax. Apply the wax with a soft lint free cotton cloth, let it
haze over, then buff it out with a clean cotton cloth. This technique
will yield a very mellow, low luster finish that is beautiful not only
to look at but to touch.
3. For A Natural Look- Simply Wax
When I have to finish a decorative wooden object that will not be
handled much, therefore needs little protection but also has to look and
feel as close as possible to its natural appearance, I simply apply a
paste wax only. Here the color of the wax is important. If you are
finishing a lighter colored wood such as teak, use a natural or clear
colored paste wax so the natural color will not change much. On the
other hand, if you are finishing a darker wood, such as rosewood or
cocobolo, I suggest you use one of the colored waxes, such as
you use a light colored wax on dark woods, the wax may build in the
pores and make the pores appear light. Dark wax will blend in better
with darker woods and even accent the pores. Briwax comes in a number of
colors. Along with clear, it is available in Dark Brown, Light Brown,
Antique Mahogany (reddish brown good for rosewoods), Golden Oak and
REMEMBER. ALWAYS TEST FINISHES AND FINISHING TECHNIQUES ON SCRAP BEFORE
USING THEM ON YOUR GOOD WORK.