Rough Stuff No. 1 – An Introduction to Sandpaper

Let’s assume that you have already been through the soul-searching exercise about removing patina and destroying the value of an antique by stripping and refinishing it. Fine.

Read Fred’s Rough Stuff No. 2 – Choosing the Right Sandpaper.

Now on to the real world, since most of us aren’t dealing with antiques when we talk about refinishing a piece of furniture, anyway. More likely, we are looking to upgrade that beat up but solid-oak chest of drawers in the kid’s room. Or maybe the object is to revive the 1950s (?) buffet found at a garage sale that looks like may be its maple under the avocado green paint from the “antiquing kit” of the 1970s.

After the piece is stripped, what happens next? The purist will say to finish it in some exotic concoction of wax and oil and leave it alone. The hack next door will recommend three coats of tinted gloss polyurethane, rubbed between coats with fine steel wool. The professional will say “sand it first.”

Sand it? Why in the world would you sand it? Because preparation is 90 percent of finishing and the best finish in the world won’t look good if the piece isn’t properly prepared for the finish. So, what exactly is the objective of the sanding process?

Most stripping and rinsing techniques expose the wood to the natural moisture of the atmosphere, even if water is not used to rinse the stripper—please don’t use water to rinse stripper because a) it isn’t good for the wood and b) if you rinse it, the stripper can get into the water system and we all get to drink it next week). This exposure to natural moisture tends to raise the fibers of the wood slightly over the course of a day or two and can make the surface slightly rough, enough in many cases to cause snags and pulls in a stain rag when wiped across the surface. So the first objective of sanding is to smooth the surface of the wood and close down the pores opened in the stripping process so the piece will accept stain and finish evenly.

Another objective of sanding bare wood is to even out the color. A piece that has seen rough duty over several years will undoubtedly show variations of color in the wood due to uneven exposure to light and moisture, even after its stripped. And unless you paint the piece, these variations will telegraph through even the most concentrated stain and clear finish. A good sanding will remove the darkness created by body oil on the worn out arms of a chair and give new life to the runners of a rocker that was water stained when the carpets were cleaned.

A final case for sanding is made when the wood is new. The term “sanded” to a lumber yard means something entirely different from what it means to a finisher. To a lumber supplier sanding is merely another way of dimensioning wood. After a tree is cut with a saw, boards are cut from the tree. Boards are re-sawed to various sizes and shapes. Then they are dimensioned again by a planer, then yet again by a coarse drum sander, all to get the wood to a specified uniform height, width and length. The finisher then has to sand it to remove the evidence of all these previous processes and prepare the wood for the finish.

Given these main objectives of sanding, what kind of sandpaper should be used and what grade?

Sandpaper in various girts.

Sandpaper is assigned a number grade—the “grit”—that specifies the size of the particles used on the abrasive surface. The numbers can range from 40, an extremely coarse grade, to more than 2000, a paper so fine it is not much more abrasive than a brown grocery bag and, when used with water, can achieve a glass-like surface. Sandpaper is also assigned a letter grade—the “weight” —which indicates the thickness and stiffness of the paper backing itself. The lightest weight and thinnest paper is usually graded as “A.” This grading system then goes down the alphabet with increasing weight as the grit gets coarse. For example, 80, 60 and 40 grit abrasives are usually found on a “C” weighted backing. Abrasives used in sanding belts or drum belts are affixed to even heavier weights to stand up to the stress of power applications.

For furniture preparation, the most often used paper is 120 or 150 grit, A weight paper, strong enough to do the job but light and flexible enough to be manageable by hand. Once bare wood has been sanded with 120 or 150, there is no need to sand it with a finer grade. Increasingly finer grades of paper tend to burnish the wood rather than abrade it and actually make the surface less amenable to stain and finish. Even worse than very fine sandpaper on bare wood is steel wool, which has two problems for bare wood. First, steel wool has oil in it to keep it from rusting in the bag and on the store shelf. If this oil is transferred to bare wood, it may not accept a stain evenly. Second, steel wool has a tendency to disintegrate into extremely fine, almost invisible particles as it is used. If these particles lay undisturbed on a bare wood surface over a damp night they can rust, causing small black “flyspecks” that are very difficult to remove. Steel wool should only be used to alter the sheen of the final coat of finish, never on bare wood and never between coats of finish. That’s what sandpaper is for.

Fred Taylor is a antique furniture Worthologist who specializes in American furniture from the Late Classicism period (1830-1850).

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Send your comments, questions and pictures to me at PO Box 215, Crystal River, FL 34423 or info@furnituredetective.com.

Visit Fred’s website at www.furnituredetective.com. His book “How To Be A Furniture Detective” is now available for $18.95 plus $3 shipping. Send check or money order for $21.95 to Fred Taylor, PO Box 215, Crystal River, FL 34423.

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) are also available at the same address. For more information call 800-387-6377, fax 352-563-2916, or e-mail info@furnituredetective.com.

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No Comments

  1. Dan Bill says:

    RIGHT. thanks!

    I wonder if using a wire brush on bare wood is okay if done carefully?

  2. Gio says:

    I’ve finished staining my furniture using iron oxide (vinegar and wool solution). I have the color that I want and was ready to coat it with a water-based polyacrylic. Problem is that I used steel wool to buff off the rust particles from the solution, which it worked but your article says never to use steel wool on bare wood. Too late.

    What can I do? Should I switch to an oil-based top coat? Do they even make oil-based top-coats that don’t yellow.

    Appreciate your help!

  3. Fred Taylor says:

    Gio – You are too deep into it now. Just go ahead with your original finish schedule and hope for the best, especially if you live in a drier climate than I do. Just get it covered in finish as soon as possible to prevent moisture from getting to it. Interesting choice of stain. How did you come up with that?

    Thanks for writing.

    Fred Taylor