Techniques and materials used to refinish wood furniture and cabinetry.
Most finishes that protect the surface of wood furniture and cabinetry are either polyurethane, shellac, varnish or lacquer. When repairing a finish coating, work only to the depth that it is damaged. Work carefully and don't remove more of the finish than you have to.
Alligatoring, Crazing, and Scratches: Alligatoring, crazing, and cracking are all basically the same thing. They're all caused either by sunlight or by temperature changes. The type of finish on the furniture determines the solvent used for reamalgamation: shellac is reamalgamated with denatured alcohol, lacquer with lacquer thinner, and a lacquer/shellac mixture with a mixture of three parts alcohol and one part lacquer thinner. Varnish finishes usually can't be reamalgamated.
Before you work on the finish, clean the piece of furniture thoroughly with mineral spirits or turpentine to remove all wax and dirt. Don't work on a very humid day if the finish is shellac; the alcohol used to liquefy shellac can draw moisture out of the air and into the finish, resulting in a haze or blushing.
Work fast when using this refinishing technique, especially with lacquer. Test on a small area to practice and once you're satisfied with your results, go on to reamalgamate the entire finish. Apply a moderate amount of solvent with a brand-new, very clean natural-bristle brush. You can purchase a store-bought amalgamator or mix your own. Use denatured alcohol on shellac, lacquer thinner on lacquer, a three-to-one mixture of alcohol and lacquer thinner on a lacquer/shellac mixture.
To reamalgamate the finished surface, apply solvent along the grain of the wood in quick, long strokes; move quickly and don't scrub the surface with a dry brush. Don't try to brush out all the cracks or scratches at this point; many of them will disappear as the finish dries. If you work on individual marks too much, you may actually be removing the finish instead of liquefying it. After the reamalgamated surface has dulled, lightly buff the finish with No. 0000 steel wool, working in one direction along the grain; do not apply too much pressure. Wipe the surface clean with a tack cloth and apply two coats of wax.
Blushing: Blushing, which is a white haze over a large surface or an entire piece of furniture, is a common problem with older shellac and lacquer finishes. The discoloration is caused by moisture.
Buff the surface lightly and evenly with No. 0000 steel wool dipped in linseed oil. Work with the grain of the wood, rubbing evenly on the entire surface, until the white haze disappears. Then wipe the wood clean with a soft cloth, apply two or three coats of hard furniture wax, and buff the surface to a shine.
Blushing can sometimes be removed by reamalgamation. If the surface is crazed, reamalgamation should be used instead of steel-wool rubbing. If neither rubbing nor reamalgamation removes the haze, the piece of furniture must be refinished.
White spots: Shellac and lacquer finishes are not resistant to water and alcohol. Spills and condensation can leave permanent white spots or rings on these types of finishes. To remove these white spots, try polishing the surface with liquid furniture polish and buff the surface firmly. If this doesn't work, lightly wipe the stained surface with denatured alcohol. Use as little alcohol as possible; too much will damage the finish.
If neither polishing nor alcohol treatment removes the white spots, the damaged finish must be treated with abrasives. Gentle abrasives can be purchased from a home-supply store. To make your own gentle abrasive, mix cigarette or paper ashes to a paste with a few drops of vegetable oil, light mineral oil, or linseed oil. Rub the ash-oil paste over the stained area, along the grain of the wood, and then wipe the surface clean with a soft cloth. You can use mayonnaise as a polish that will also remove water stains. Place a spoonful of mayonnaise on a soft cloth and rub the area in a circular motion. Buff until dry. You may also add ashes to the mayonnaise to create an abrasive. If necessary, repeat the procedure. Stubborn spots may require several applications. Then wax and polish the entire surface.
If rubbing with ashes is not effective, go over the stained area with a mixture of rottenstone and linseed oil. Mix the rottenstone and oil to a thin paste, and rub the paste gently over the stain, along the grain of the wood. Rottenstone is a fast-cutting abrasive, so rub very carefully. Check the surface frequently to make sure you aren't cutting too deep. As soon as the white spots are gone, stop rubbing the finish and wipe the wood clean with a soft cloth. Apply two coats of hard furniture wax and buff the wood to a shine.
Black spots: Black spots are caused by water that has penetrated the finish completely and entered the wood. They cannot be removed without damage to the finish. You may be able to remove the finish from an entire surface only; if not, then the entire piece of furniture will have to be stripped. When the finish has been removed, bleach the entire stained surface with a solution of oxalic acid. Then refinish as necessary.
Ink stains: Ink stains that have penetrated the finish, like black water spots, cannot be removed without refinishing. Less serious ink stains can sometimes be removed. Lightly buff the stained area with a cloth moistened with mineral spirits; then rinse the wood with clean water on a soft cloth. Dry the surface thoroughly, and then wax and polish it.
If this does not remove the ink, lightly rub the stained area, along the grain of the wood, with No. 0000 steel wool moistened with mineral spirits. Then wipe the surface clean and wax and polish it. You will probably need to refinish the damaged spot. If the area is badly damaged, the entire surface or piece of furniture may need to be refinished.
Grease, tar, paint, and crayon: These materials usually affect only the surface of the finish. To remove wet paint, use the appropriate solvent on a soft cloth; mineral spirits for oil-base paint and water for latex paint. To remove dry paint or other materials, very carefully lift the surface residue with the edge of a putty knife or wooden skewer. Do not scrape the wood, or you'll scratch the finish. When the surface material has been removed, buff the area very lightly along the grain of the wood with No. 0000 steel wool moistened with mineral spirits. After the material has been removed, wax and polish the entire surface.
Wax and gum spots: Wax and gum usually come off easily, but they must be removed carefully to prevent damage to the finish. To make the wax or gum brittle, press it with a packet of ice wrapped in plastic wrap or a paper towel. Let the deposit harden; then lift it off with your fingernail. The hardened wax or gum should pop off the surface with very little pressure. If necessary, repeat the ice application. Do not scrape the deposit off, or you'll scratch the finish.
When the wax or gum is completely removed, buff the area very lightly along the grain of the wood with No. 0000 steel wool moistened with mineral spirits. Then wax and polish the entire surface.
For some light surface scratches, use lemon oil which will darken the scratch and raise the grain. Lemon oil puts moisture back into wood furniture, which should be wiped down with the oil at least once a year. The only wood that should not be used with lemon oil are those with high-gloss surfaces. Lemon oil comes in two colors, light for lighter woods such as oak and maple and dark for woods like walnut and mahogany.