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Refinishing Furniture
A very satisfying sideline
TEXT AND PHOTOS BY BOB FLEXNER
When I started my woodworking shop over 30 years ago, my intention was to build furniture. But the reality of making a living interfered. Not only did I struggle getting enough commissions to keep me busy full time, I also found it difficult to charge enough. I quickly discovered that refinishing paid better and the time involved was easier to estimate.
Even if you are not a professional with an income issue, you may find refinishing furniture enjoyable. One benefit is you quickly become comfortable with finishes, a goal most woodworkers who finish only what they make rarely achieve.
APPROACHES
There are three broad approaches to refinishing: make the furniture look new (as the maker or factory intended it to look, including using the same finish the maker used); make it look old but in good shape; and make it look like something else (for example, change the color). All three are legitimate, depending on the wishes of the owner of the furniture.
The owner is always the final arbiter, though you surely play an advisory role if the owner is requesting something you don't consider wise—for example, using polyurethane instead of shellac on an eighteenth-century highboy or elaborate Victorian sideboard.
I find the first two approaches the most satisfying, with the second the one I usually adopt unless otherwise instructed. For this article I'm using a 1920s mass-produced Pembroke table for illustration purposes.
REVIVING THE OLD FINISH
Before beginning it's always wise to consider the possibility of reviving the existing finish. Not only will this preserve the original, or existing “old” finish, which the Antiques Roadshow has conditioned people to value [see Woodwork #100, August 2006, page 54], but it will take much less time than refinishing.
Color damage can often be touched up with pigment or dye stain, or with stain and finish mixed (thin paint). White (not dark) water rings can be removed by rubbing with a fine abrasive or with a light alcohol wipe. And dullness and light scratches can often be removed by rubbing with fine abrasives or coating over with more finish, even using the French Polishing method.
With this Pembroke table, however, repairing the finish was not a good option. Problems included sectional bleaching and water-marking (1), severe scratches (2) and crazing (3). When a finish crazes, it no longer serves its function as a moisture barrier. This can lead to warping, splitting and the lifting of veneer on tabletops, which are often exposed to water [see Woodwork #100, August 2006, page 58].
Once it's decided to refinish, the first step is usually to do as much of the wood repair, including regluing, as possible so glue seepage and minor damage occurs on top of the old finish rather than on bare wood. This seepage and damage is then removed with the finish. An exception is when you have to strip paint first to get the right match for a veneer repair.
STRIPPING
To get a better understanding of what's involved in stripping, it will help to understand what is being stripped. Almost all old furniture was finished originally, or refinished later, with shellac or lacquer [see Woodwork #111, June 2008, page 34]. These are both evaporative finishes that dissolve with alcohol or lacquer thinner. So you can use these solvents to remove the finish on most old furniture.
To determine whether the old finish is shellac or lacquer, rub a little of each solvent onto an inconspicuous area to see which dissolves the finish. This table was clearly finished with shellac (4).
Or, you can use a commercial paint stripper, which is faster but has the disadvantage of leaving a wax residue on the surface that you then have to wash off (not “neutralize,” as instructions universally say) with a solvent such as mineral spirits. This is a critical step, because if you don't get all the wax off the wood, the finish you apply may not dry or bond adequately.
To use the finish's solvent for stripping, cover the surface with several layers of cloth or paper towels and wet them thoroughly with the solvent (5). Keep them wet until the finish dissolves and you can simply wipe it off (6).
There are five categories of strippers (7). The three on the left of the photograph all contain wax. From left to right the strongest is high-percentage methylene-chloride, which you can identify by the “non-flammable” claim on the label or by its weight, which is noticeably greater than the other strippers. Then there's low-percentage methylene-chloride and no methylene-chloride. Refinisher contains no wax or methylene chloride. It is essentially lacquer thinner. The stripper in the plastic container is n-methyl pyrrolidone (NMP). Contrary to the claim on the label that it works in 30 minutes, it takes many hours or several days. But it is very effective if given enough time and is actually my favorite when I'm not in a hurry.
To use a commercial stripper, brush it on the surface with a minimum of brush strokes so you're disturbing the wax that's slowing evaporation as little as possible (8). When the finish has dissolved, scrape off the majority into a cardboard box (9) and then wash off the remainder with the solvent for the finish (10). Continue with a second and third washing, using the same solvent or mineral spirits to remove all the wax.
Steel wool can be helpful for dislodging stubborn finish, but it's less work to let the solvent or stripper do the job instead.
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SANDING
With the wood stripped, the surface needs to be prepared for a new finish. It's here that one of the most time-wasting and damaging misunderstandings occurs. There's seldom a need to coarse sand stripped furniture.
All factory and good quality hand-made furniture was sanded or smoothed with hand tools when it was made. There are no longer any mill marks to be sanded out.
Furthermore, deep sanding removes evidence of age, the crispness of carvings, turnings and molding, and can cut through veneer.
It's still wise, however, to do a light sanding with very fine sandpaper to check that all the finish has been removed. Any remaining finish will gum up the sandpaper and you will know that more stripping is necessary. Don't be tricked by stain, thinking it is finish. No stripper will remove all the stain, and you don't need to remove it unless you want to make the wood lighter. Usually, the less sanding the better.
It's also not necessary, and often unwise, to back your sandpaper with a sanding block because old surfaces are seldom flat anymore. Sanding lightly by hand with fine sandpaper won't create noticeable grooves in the wood.
DARK WATER MARKS
Water penetrates easily through a crazed finish and often stains the wood dark (11). You can sand out the stain, but it will be a lot of work and you risk sanding through veneer. It's much easier and less risky to bleach the stain using oxalic acid.
Oxalic acid is commonly sold as wood bleach, but it's not the same as household bleach or chlorine bleach sold for swimming pools. Nor is it the same as two-part bleach, which is also sold as wood bleach and will take all the color out of the wood.
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To make a strong solution of oxalic acid from the crystals, dissolve them in hot water until the water is saturated (12). No more crystals dissolve; they settle to the bottom.
Brush a wet coat of the solution on the stripped wood. Brush the entire surface so any color changes the solution might cause will be uniform overall (13).
Allow the oxalic acid to dry on the wood. It will return to its crystal form (14) and you have to wash off these crystals. Don't brush them into the air because they will cause you to choke if you breathe them. Wash into a bucket of water (15) or take the parts outdoors and hose them off.
When the wood dries, the watermark should be gone (16), but you can repeat the procedure if it isn't. (Note that it's rarely possible to remove ink stains with any method other than sanding them out—and they usually go very deep in the wood.)
There's a long-standing myth in the woodworking community that you need to neutralize the oxalic acid with vinegar. The first mention I can find of doing this is in the Winter 1977 issue of Fine Woodworking, page 33. This procedure is, of course, absurd, because you don't neutralize an acid with another acid. But once an incorrect instruction gets into print it seems to take on a life of its own, and this one has been repeated many times in almost all woodworking magazines, even as recently as in the January 2008 issue of American Woodworker, page 56.
If you wanted to neutralize the wood, you'd use a base liquid such as baking soda or weak household ammonia. But oxalic acid isn't a strong enough acid to require neutralizing. It won't affect the bond of any common finish, or interfere with its drying, or cause a problem later if water gets through the finish and into the wood. There's no need to neutralize oxalic acid.
STAINING
Most old furniture was stained when it was made, or the wood has changed color (usually darkened) due to oxidation. Sometimes sun exposure has bleached the wood lighter.
For various reasons, it's often necessary to apply a stain. You can use a common oil stain from the paint store, of course, but you usually get richer, deeper and more even results using a water-soluble dye stain. The most effective brand is W. D. Lockwood [www.wdlockwood.com], which is sold by several mail-order suppliers under the Lockwood name and by Woodworker's Supply under the J. E. Moser brand name.
I like these dyes for two primary reasons. First, they are available in dozens of colors, which correspond to the colors of old and antique furniture—Phyfe Red, American Walnut, Fumed Oak, Antique Cherry, etc. Second, unlike Solarlux, Transtint and other metalized dyes, Lockwood dyes can be lightened significantly right on the wood simply by wiping over with a wet rag after the dye has dried. I find this characteristic extremely useful for achieving closer color matches on old furniture.
Lockwood dyes come in powder form, ready to be dissolved in water (17). You don't need to use distilled water as is sometimes suggested, and you don't need to use hot water unless you want to make an intensely dark color (hot water absorbs more dye).
If you get the color too dark, as I did here on one of the drop leafs (18), simply wipe over with water (19) to remove some of the color until you get a match after the wood has dried (20). The Lockwood powder dyes are wonderfully forgiving.
Whichever stain you use, the basic method of application is to apply a wet coat and wipe off the excess before the stain dries (21). You can use any application tool, but sponges and rags are the fastest (assuming you aren't using a spray gun). Soak the sponge or rag and wipe over the surface quickly. Then remove the excess with a dry cloth.
FILLING PORES
Most furniture from the mid-nineteenth to the mid-twentieth centuries was made with porous woods such as mahogany, walnut or quatersawn oak, and the pores were filled during the finishing process. Refinishing these woods without filling the pores can have a surprisingly negative effect on the appearance, especially on tabletops, which catch reflected light.
You can fill the pores by applying many coats of finish and sanding them back, but it's easier and less wasteful to use paste wood filler instead.
Before doing the filling it's best to apply a washcoat so streaks of filler you might inadvertently leave can be sanded off without cutting through stain color. A washcoat is any finish thinned to about 10% solids (varnish thinned with about two parts mineral spirits, lacquer thinned a little over half with lacquer thinner, or a 3/4-pound cut of shellac).
The best finish to use as a washcoat when refinishing is shellac because it blocks silicone, which will cause varnish and lacquer to fish-eye. Silicone is a synthetic oil added to many furniture polishes to increase shine and scratch resistance. It gets into the wood through scratches and crazing and isn't fully removed in the stripping.
Notice how the water fish-eyed when I brushed the oxalic acid solution (22). This is a sure indication there is silicone in the wood, which will cause a finish to fish-eye just as this water is doing. (You can also use a wet coat of stain or mineral spirits to test for silicone.)
Paste wood filler is varnish with silica (a solid material similar to fine sand) added to provide the filling. A few brands such as Behlen's are available in various colors. Most are neutral filler to which you have to add a concentrated colorant (oil, Japan or universal) because the filler won't take stain well.
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The easiest method of applying the filler is to thin it enough so it is easy to brush (23). Use mineral spirits for a long working time or naphtha for a short working time. Brush the filler onto the wood evenly like brushing paint (24), and allow it to dry to a dull sheen. Then wipe it off across the grain so you remove as little as possible from the grain. Use a cloth or paper towel if the filler is still soft enough (25). If it gets too hard, use burlap, which is coarser but not so coarse that it scratches the wood (26).
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If the filler dries too hard for the burlap to remove it, wash it off with a cloth dampened with naphtha or mineral spirits and reapply in smaller areas. As long as you have applied a washcoat, you won't get lap marks because you're leaving the filler only in the pores.
Because the filler shrinks a little as it dries, you'll always get better results if you apply a second coat after the first has dried overnight.
After the filler has dried, sand it lightly with 320- or 400-grit sandpaper to remove any residue you might have missed in the removal process.
TONING
If you are spraying lacquer or shellac, you can further adjust the color by toning. A toner is a little finish with a little color and a lot of thinner added. It's best to spray toner because brushing could leave darker streaks from the thicker brush marks.
To make a toner, take about one part finish (lacquer or shellac) and thin it with six or more parts lacquer thinner or alcohol. Then add a little color, with the best type being a metalized dye—for example, Solarlux or Transtint. Begin with very little color to avoid overdoing the adjustment. You can always add more dye or apply more coats, but you'll have to strip and start over if you get the color too dark using shellac or lacquer.
In addition to getting a more even color layer, the purpose of thinning the finish so much is to keep each toner coat very thin so you can apply many coats with almost no build.
GLAZING
It's easy to add fake age by applying a dark glaze (usually brown or walnut color) to recesses in the wood, such as in carvings, moldings and turnings. Glaze is thickened stain (so it won't run) very similar to gel stain. In fact, you can use gel stain as a glaze.
Working over at least one coat of finish, so the glaze doesn't get into the wood, wipe or brush it on and then wipe it off all the areas where you don't want it. Leave it in the recesses. If you don't like the effect, wash off the glaze with mineral spirits for oil-based glaze or water for water-based glaze.
After the glaze has dried, apply at least one additional coat of finish to protect it from being rubbed or scratched off.
FINISHING
The final step is to apply a finish. There are three good choices: shellac, lacquer or varnish (including polyurethane varnish). Here is the reasoning for each.
Shellac may keep with the original finish. As long as the shellac is freshly dissolved, it is quite water resistant and will perform well. Shellac's only downside is that it is glossy, so you will have to rub it with #0000 steel wool if you want a satin sheen. Both the glossy look and the rubbed look will make the finish look new rather than old.
Lacquer is a good choice if you have a spraying option (you can also spray shellac, of course). The advantage of lacquer over shellac is that it is available in flatter sheens, which come closer to resembling a finish that is old but in good shape.
For maximum water and scratch resistance you can use alkyd or polyurethane varnish, which are also available in flatter sheens. To avoid brush marks, thin the varnish about half with mineral spirits and brush or wipe it on the surface, or use a commercial brand of wiping varnish (see Woodwork #108, December 2007, page 34). For a wiped-on satin sheen, you'll get more even results using a gel varnish.
Bob Flexner is the author of
Understanding Wood Finishing.