Tag Archives: shellac

Finishing Furniture

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Egyptian Table

Egyptian Table

Detail Egyptian Table

Detail Egyptian Table

The finish is usually the last thing that you do when building a piece of furniture, but it is the first thing that someone sees when looking at your work.  You can do a great job designing and building a piece of furniture, but if the finish is of poor quality it will devalue the entire piece.  Finishes can be divided into two main categories:  air oxidizing finishes and solvent release finishes.  Air oxidizing finishes cure by reacting with oxygen and this category includes oils, varnishes, and urethanes.  Solvent release finishes cure when the solvents evaporate into the air, leaving a layer of resin on the surface.  Finishes in this category include shellac, lacquer, and some water based finishes.

No matter which type of finish you select, keep in mind that approximately 60% to 70% of a good finish is surface preparation.  That means scraping and sanding until all saw marks, mill marks, etc, are removed.  Tabletops are the most critical and need to be examined in raking light.  That means placing a light source near the table and positioning yourself so that you can see the light reflect off the top.  As you move around, your eyes should be able to scrutinize every square inch of the top, revealing any scratches, flaws, high spots, or low spots.

Generally speaking, I prefer a hand rubbed oil finish for most of the furniture that I build.  Linseed oil and Tung oil are the two most commonly used oils in finishes and both of them have withstood the test of time.  Linseed oil is derived from the flax plant and has been used since the ancient Egyptians.  Tung oil is derived from the nuts of the Tung tree which grows in the Far East and was used to help preserve the Great Wall of China.

 Both of these oils penetrate the structure of wood cells creating a finish that is “in” the wood as opposed to being “on” the wood.  Applying multiple thin coats will create depth and accentuate the figure of the wood.

Oil finishes do not offer the same resistance to moisture that film finishes like lacquer and polyurethane do, but the trade off is that they allow for a very natural looking finish and permit you to experience the tactile quality of the wood.  In addition, they are easy to repair.  If the surface looks worn, you do not have to strip it and sand it; you simply rub in another coat of oil.  I have also found that they can be enhanced by lightly rubbing with 0000 steel wool and applying a light coat of wax.

Note:

I will be teaching a 5 days hands on class on Finishing in my Workshop/Studio here in Santa Rosa, California on August 1 – 5, 2013.

Finishes that I will cover in the class include: shellac, various oils, as well as lacquers and polyurethanes. For those that have seen Woodworks, I will cover in depth my technique for applying hand rubbed oil finishes which are also known as wiping varnishes.

Here is the link to the Classes Section of my website that gives the class description and registration information.

Finishing Class

Finishing Sample Boards

Finishing Sample Boards

If you would like to see pictures from previous Finishing Classes I have taught in my Workshop/Studio, here is the link to the Classes Photo Album:

2012 Finishing Class

2012 Finishing Class

Finishing Class Pictures

The Benefits of Shellac for Restoring Wood Surfaces

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Question from a Client

David,

I bought this very old Chinese tray with half the lacquer worn off.  I want to preserve what is left and use it to work on.

Can I paint or spray some kind of clear finish on it?  You are our guru for surfaces on wood.  All I know is textiles.

Thanks for your help.

Barbara

David’s Response:

Shellac is your best bet as shellac will stick to almost anything, and almost any finish will bond to shellac.

Shellac by Bulls Eye

You can purchase shellac flakes and mix your own 2 lb cut with denatured alcohol but this shellac by Bulls Eye works really well and is very convenient to use.  The most important part of application is temperature and humidity conditions.  Make sure you work with  a scrap piece of wood and do some test samples before applying it to your piece.

The ideal conditions would be a sunny day with temperatures around 75 to 80 degrees.  If it is a rainy or overcast day, then do not spray shellac, wait for a dryer day.  Shellac can absorb moisture from the air on a day with high humidity levels and the result will be a “milky”color to the finish.  If you can spray it indoors in your studio, then make certain that the room/space has a thermometer in it and it reads 75 degrees or warmer for best results.

When I work on a piece that I am restoring, I lightly clean the surface first and try to remove any wax that has been applied over the years.  I use to use Naphtha, but it has been removed from California’s hardware and paint stores for health reasons.  Old Asian lacquers are Urushi lacquers which are natural resin from the Sumac trees.  Shellac is a natural resin harvested from the Lac bugs in India and other Asian countries.  Even if you are not able to light clean the surface with a mild solvent, I believe the shellac will still bond to it.  Cleaning the surface first is still your best option.

Since Naphtha is no longer available, I would try some mineral spirits instead.  Before using the mineral spirits, start by lightly brushing the surface with a soft, dry paint brush to see if the old finish flakes off or is still intact.  Once you have lightly brushed the surface and removed any dust or loose material from it, then take an old t-shirt or clean cotton cloth and moisten it with some paint thinner (you can purchase the odorless type which is more user friendly) and gently rub the surface.  Do not use any abrasive material like steel wool or scotchbrite, it can remove some of the finish.

Let the surface dry.  It might look dull as a result, but it should be cleaner.

Shellac flows best when it is warm.  When I spray it from a solution I have mixed or from a can, I always try to warm it first.

Cans are much easier to deal with.  On a sunny day, simply leave the can in the sun until the can feels warm to your hands.

I have an oil filled radiator in my finishing room and I place the can on it until it feels really warm or you can just place the can next to a light bulb as a heat source.

Shake the can really well, and use long, light, uniformly even strokes across the surface, overlapping each stroke.  The goal is to apply a light, wet, uniformly thin coat over the entire surface.  The surface should look glossy without any dry spots but do not apply too much at a time to the point where it puddles or runs.

The great thing about shellac is that in addition to protecting the surface, it also acts like a coat of glue bonding everything together.

You might want to apply several coats depending upon how it looks.  Apply a second coat of shellac before doing any sanding so as not to damage the original finish.  After the second coat has dried, then lightly sand it with  some 600 grit sand paper to smooth and blend the old and new surfaces.  Try not to cut through the shellac into the original finish, but if you do, just apply another coat of shellac.  After the last coat of shellac has dried overnight, you could lightly rub it with 0000 steel wool to further smooth and blend everything.  I like to follow up with a light coat of Renaissance wax to bring up the soft sheen after it has been dulled by the steel wool.

Please remember to practice on test pieces first before working on your prized possession.