Rejuvenating Old Finishes: Three Tips in OnePosted on March 8th, 2011 No comments
Think of wood finishes as plastics. Depending on how broadly you define “plastic,” this is exactly what they are. And just like all plastics, finishes deteriorate over time—faster in bright light and heat. First the finish dulls; then it begins crazing and cracking.
As the deterioration gets worse, the finish loses its primary function of slowing moisture (liquid and vapor) exchange. Excessive moisture exchange leads to veneer cracking, joints and veneer separating, splits in wood and warping. A deteriorated finish also looks bad.
Old furniture with deteriorated finishes usually end up in city landfills. This is the reason the message of the Antiques Roadshow, “Don’t refinish!” is so unfortunate. Refinishing saves old furniture with deteriorated finishes.
Often, however, finishes can be repaired rather than refinished. And just as there are different levels of deterioration, there are different levels of repair. Here are three, advancing from least to the most intrusive, effective and difficult to pull off.
Clean the Surface.
Sometimes great improvement can be achieved simply by cleaning (as I’ve done to the left side of the crest rail on the chair). There are two types of dirt, water-soluble and solvent (paint-thinner) soluble, so you may need to use both types of cleaner.
Cleaning won’t remove finish in good condition, but it will remove the dirt. And sometimes that is the major problem.
If the cleaning removes all the finish down to the wood, the finish was totally deteriorated and should be replaced with new finish to protect the wood.
Apply Paste Wax.
Paste wax is the best furniture-care product for deteriorated finishes because it adds shine, doesn’t highlight cracks as liquid products do, is fairly permanent, and it is fully reversible—meaning that it can be washed off with mineral spirits without damaging the finish underneath.
If there are lighter colored nicks and scratches, you can use a colored paste wax to color these in. Many imported brands of paste wax are available in colors.
The easy way to apply paste wax to large surfaces is to put a lump of the wax inside a cloth and wipe it over the surface. The cloth will limit the amount of wax you are depositing so you won’t have to work harder than necessary to remove the excess.
When the shine of the applied wax disappears and the wax develops a noticeable resistance when rubbed, rub off all the excess with a soft, clean cloth. Keep turning and changing the cloth so you aren’t just smearing the wax around; you are transferring it from the finish to the cloth.
Abrade the Surface.
If the finish feels rough because it is beginning to craze and crack, you can abrade it smooth, then apply paste wax or more finish on top. Sandpaper is best for leveling the surface. Steel wool and abrasive pads merely round over unevenness.
Abrading removes the top surface of the finish, which serves doubly to clean dirt. Don’t abrade through any color, whether in the wood or in the finish, or you may lose control and end up having to refinish.
Always use a sandpaper grit that removes the problem efficiently without creating larger than necessary scratches that then have to be sanded out. Generally, you would use either 400-grit or 600-grit sandpaper. You can sand the finish with dry sandpaper, in which case the sandpaper may clog, or you can use an oil or mineral spirits lubricant to prevent the clogging.
When the surface is smooth, you can apply more finish on top. The only finish that could cause problems is lacquer, or any finish that thins with lacquer thinner, because the lacquer thinner could cause the remaining old finish to blister. I would suggest using wiping varnish for a gloss sheen, gel varnish for a satin sheen or, especially for high quality antiques, shellac applied using the French polishing technique.
Fall Back Solution.
If none of these techniques work to your satisfaction, you may need to strip the old finish and apply a new one. Stripping is always better than sanding because sanding to the wood can’t help but remove the color changes (patina) and nicks and scratches that give old furniture its character.
Remember that it’s always best to keep the finish on old furniture in good condition so the furniture survives.