Popular Woodworking 2001-08 № 123, страница 62
the lubricant. The more oily or pasty (mineral oil or paste wax) the lubricant, the slower your cutting action and the higher the sheen or gloss you'll get. The more watery the lubricant (water, soap-and-water, or paint thinner), the faster you'll cut and the lower the resulting sheen. (Products with names such as "Wool Wax" or "Wool Lube," which are sold as rubbing lubricants, are simply soap in paste form - like Murphy's paste soap.) There are other abrasives you can use instead of steel wool. These include Scotch-Brite pads and pumice (finely ground lava). Gray Scotch-Brite (sold as "fine") is close in grit to #000 steel wool. Pumice, which you mix into a sludge with water, paint thinner or mineral oil and apply with a felt or cloth pad, is equivalent to #0000 steel wool. Leveling and Abrading Using Sandpaper Rubbing the finish with steel wool, Scotch-Brite or pumice merely smooths and rounds over the imperfections. To remove them entirely, you should sand with sandpaper. Sanding a film finish is just like sanding wood except you almost always use much finer grits (320 and up), and you have to use a lubricant to keep the sandpaper from clogging and damaging the surface. If the surface is flat, you should back the sandpaper with a flat cork, felt or rubber block. (I find cork works the best. You can make a fine rubbing block by gluing some Vs" gasket cork onto a light pine block about 1" thick and chamfered on the topside to conform to your hand.) Choose a grit sandpaper that removes the flaws efficiently without creating greater work than necessary taking out the sanding scratches. If you don't have any idea what grit to start with, begin with 600-grit, sand a little, remove the lubricant and see what progress you've made. If you haven't completely flattened the surface with 10 or 15 strokes over the same area, drop back to a coarser grit and continue dropping back until you find a grit that flattens the surface quickly. The most common lubricants to use are water, soap-and-water, mineral oil and paint thinner. If the sandpaper (always the wet/dry type) still clogs with water or soap-and-water, use mineral oil or paint thinner. You can mix them to control the viscosity. Pour some of your chosen lubricant onto the surface and begin sanding. As long as you intend to move up to a finer grit, there's no reason to sand only in the direction of the wood grain. The finish doesn't have any grain, so you can sand in any direction as long as your final sanding with your finest-grit sandpaper is in the direction of the grain (to disguise the sandpaper scratches). I usually begin by sanding in circles, except on the edges where I sand along them, not into them. By changing direction with each grit, it's easy to see when you've removed all the scratches from the previous grit and it's time to move on. After flattening the entire surface, which you easily can check by removing the lubricant and viewing in a reflected light, remove all the lubricant and move up to the next sanding grit. To remove oil and paint-thinner lubricant, I wipe with naphtha, which evaporates very fast. If you intend your final sheen to be that of #0000 steel wool or pumice, there's no reason to sand above 600-grit because these are equivalent. But if you want a higher gloss, you should continue sanding with 1,000-, 1,200-, 1,500- and even 2,000-grit until you're just below the sheen you want. Then switch to a commercial rubbing compound or rottenstone (finely ground limestone) and water or oil. It should be obvious that there's some experimentation involved in perfecting your rubbing technique. I recommend you make up a sample surface on a fairly decent size piece of veneered plywood by applying three or four coats of your favorite finish, and then rub it out. If you should, by chance, complete the job the first time without rubbing through somewhere, then continue until you do rub through so you can learn how much work it takes to do this and see what it looks like. PW Bob Flexner is a nationally known finishing expert in Norman, Oklahoma, and the author of "Understanding Wood Finishing." 75 |
