Almost every book you read about furniture restoration — along with almost every article posted on the Internet or printed in local antiques trade papers — touts the use of steel wool as a stripping tool and as a mild abrasive to be used in place of sandpaper. Many products associated with the furniture care and restoration industry recommend steel wool in their instructions and suggestions.
It supposedly is inert, safe, nontoxic, nonreactive and nonflammable. What could be safer? The facts about commercially produced steel wool are slightly different. In fact, if you run a commercial business that uses steel wool and if you have employees, you are required to keep a Material Safety Data Sheet on the stuff on the premises and open for inspection. OSHA requires an MSDS on almost all chemicals and products used commercially.
A standard experiment in high school chemistry and physics classes involves steel wool and may demonstrate its potential power. The experiment starts with soaking the steel wool in vinegar. Why? Did you ever see a package of rusty steel wool on the shelf at the hardware store? No. The reason is that the spun steel fibers have a microscopic coating of oil to prevent them from rusting. Soaking in vinegar removes this protective coating. After wringing out the steel wool pad, it is wrapped around a thermometer and placed in a sealed jar. After a few minutes, the temperature rises because of the reaction that takes place when four atoms of iron react with three atoms of oxygen and create two atoms of iron oxide – rust!
You can unwittingly re-create this experiment by using steel wool in the process of removing one or more layers of finish from a piece of furniture. The stripper in which the pad of steel wool is dipped acts as a substitute for the vinegar in the experiment and is actually a much better solvent for removing the oil from the steel wool than the vinegar. Then, as you work the product across the surface of the furniture, the finely spun web of steel fibers begins to disintegrate, leaving tiny, invisible flecks of raw steel on your work surface.
While the process is slower, the results are the same as those in the chemistry experiment. Overnight, the steel flecks react with oxygen, creating tiny, solid pieces of rust on your furniture. But unlike regular rust, they are not orange, because they have further reacted with the tannin in the wood. As a result, the flecks of iron oxide are now black. They look like pepper sprinkled across your work — and you had better be fond of pepper, because they are extremely hard to remove. You may have luck sanding them out. You may have some luck bleaching them out. Or you may just have to get used to them.
How can you avoid this? Don’t use steel wool to remove a finish. Use a stripping pad or a slightly abrasive poly pad. These pads can be rinsed out and used again. They will not rust.
It is partially for the same reason that steel wool should never be used to smooth raw wood. Wood doesn’t need to be any smoother than what most medium or fine grades of sandpaper can produce. Steel wool is not that good an abrasive anyway. It has a tendency to “ride over” obstacles rather than cut them down. But more importantly, the steel fibers will snag on the uneven grain of raw wood and generate microscopic steel flecks that could cause the same type of staining in the wood, even without the use of a solvent to remove the protective coating from the steel wool fiber.
Another common use for steel wool, especially touted by non-professional “experts,” is to rub out or smooth out intermediate layers of finish, such as polyurethane or lacquer. In this case, the presence, not the absence, of the protective coating of oil employed by the manufacturer can interfere with the work. By scrubbing an intermediate layer of finish with steel wool, the protective oil is distributed across the surface of the finish and can cause extreme adhesion problems for the next coat of finish. Extreme cases can even produce “fish eyes” in the finish. No finish, except an oil finish, reacts well to being applied over a thin film of oil. For smoothing out intermediate coats of finish, use fine sandpaper — 320 grit is an excellent all-around choice, 220 grit if you have major dust or contamination problems, 400 grit if you are using shellac.
The final inappropriate use of steel wool is in cleaning metal hardware, again, often recommended by nonprofessionals but seldom actually used in the trade. Steel wool has a tendency to scratch or dull softer metal hardware, especially brass. There is no substitute for a good metal cleaner, a soft rag and a little patience.
What is the appropriate use for steel wool? Steel wool is an excellent choice for an intermediate step in the rubbing process required to produce a high gloss lacquer finish, used between sandpaper and the various rubbing and polishing compounds. It also is an excellent choice for knocking down the sheen on any finish that is too bright, especially around edges and on corners.
In the furniture trade, steel wool’s use is limited to producing results after a finish has been applied — never before and never during.
Send your comments, questions and pictures to Fred Taylor, P.O. Box 215, Crystal River, FL 34423 or visit Fred’s website. His book “How To Be a Furniture Detective” is available for $18.95 plus $3 S&H. Also available is Fred and Gail Taylor’s DVD, “Identification of Older & Antique Furniture,” ($17 + $3 S&H) and a bound compilation of the first 60 columns of “Common Sense Antiques by Fred Taylor” ($25 + $3 S&H). For more information call 800-387-6377, fax 352-563-2916 or email@example.com.
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