To determine what the finish is before beginning to work on it, you can conduct tests employing two solvents, denatured alcohol and lacqucr thinner.
Denatured Alcohol Paint stores carry denatured alcohol for use in thinning shellac. Find an inconspicuous spot on the furniture (the underside of a runner or rung) and clean off all wax. if you haven't already done so. Now moisten a small cotton swab or a soft cloth with denatured alcohol and rub the area. Rub for at least 10 minutes, remoistening the applicator regularly. If the finish is shellac, it will soften. You will sec some of it on the applicator, and it will tend to spread over the surface you are rubbing. If it docs not soften, then you know you have another kind of finish — possibly varnish or lacquer.
Lacquer Thinner Next, apply lacquer thinner in the same manner. (Be sure to use the denatured alcohol first, then the lacquer thinner. Denatured alcohol will not affect a lacquer finish, but lacquer thinner may soften shellac.) Lacquer thinner will readily soften a lacquer finish, but will not affect a varnish.
Varnish By applying these two tests you go through a process of elimination.
and discover whether the finish is shellac, lacquer or neither. If the answer is neither, you probably have a varnish. Not much factory-made furniture was varnished because varnishing is a slow and delicate process, but the piece may have been custom-made. or it may have been rcfinished at a later date by someone like yourself who used varnish.
Bare Wood There is one other older finish to look for — bare wood finished with nothing more than linseed oil or wax. If the piece appears to have no finish coat at all. this could be what you have. Some of these pieces were stained, and some weren't. The final finish was oil or wax, applied generously and rubbed in. Many such pieces have a heavy buildup of finish, and if they haven't been cared for, an equally large collection of surface dirt that has clung to the oil or wax.
This finish presents problems. Because no new finish will adhere to the wax or oil, the old finish must be completely re moved. Use mineral spirits or remove the wax, and a paint remover to take off the linseed oil. If the oil or wax has soaked into the wood to any great depth, removal may be very difficult.
Modern Finishes There is a whole spate of modern synthetic varnishes and resins, and they all have one outstanding characteristic. They are tougher than their earlier cousins and wear very well in normal. everyday use. However, some of them, such as the penetrating resins, soak down into the wood and can be nearly impossible to take off.
Because of their toughness, these finishes are much more likely to be in pretty good shape, so you probably won't have to remove them. Not much manufactured furniture is being finished in these synthetics: lacquer is still the favorite. But the paint chemists arc at work on ways to get these products to dry faster. As the drying time decreases, more manufacturers will use them.
TESTING AND Before starting to REPAIRING THE heal those visible SOUNDNESS wounds such as OF THE FINISH dents, water stains and cigarette burns, make sure that the present finish is sound. If not, it must be removed, procedures for which are discussed in the next chapter. Once in a while, you'll find a finish that looks pretty good, but actually has become dry and brittle and will Hake away from the wood under any kind of pressure. Or it has absorbed dirt and skin oil and has become gummy. The latter defect is found on the arms of wood chairs. People have sat in these chairs with their hands and arms resting on the surface and their skin oil has penetrated the finish.
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Wood finishing can be tricky and after spending hours on building your project you want to be sure that you get the best outcome possible. In The Complete Guide To Wood Finishing you will learn how to get beautiful, professional results no matter what your project is, even if you have never tried your hand at wood finishing before. You will learn about every step in the wood finishing process from a professional wood finisher with years of experience.