To create the smoothest oil finish possible, sand the second and each subsequent coat while it is still wet with finish before wiping off using grit Pgrit sandpaper, as shown above.
After spending countless hours building a project, you naturally want the finish to be perfect. To achieve that you need to understand the one thing that separates an OK finish from a great one. A great finish feels smooth! You run your hand over the finish.
If it feels rough, you disapprove though you might not say anything. A Great Finish is a Smooth Finish Of course, there are also other factors, including thorough wood preparation to remove machine marks, dents and tear-outs, and achieving an even coloring — problems addressed in previous articles in this magazine.
But when it comes down to it, the one factor that separates a great finish from Worthwhile rub down average finish is smoothness. You achieve a smooth finish by rubbing it.
This is the only way. There are two significantly different types of finish: Oil finishes are penetrating finishes.
Oil finishes include boiled linseed oil, tung oil, and a mixture of varnish and one or both of these oils. All finishes that harden are film-building finishes.
They can be built to a greater thickness on the wood by leaving each coat wet on the surface to dry. Oil Finishes You can create a fairly smooth Worthwhile rub down finish by sanding between coats using very fine grit sandpaper grit or finer.
Be sure to allow each coat to fully cure, which means leaving overnight in a warm room.
Sand over all areas with three or four back-and-forth strokes. Above grit, P-grade numbers move up much faster than non-P-grade. Sandpaper of grit is approximately equivalent to P grit; grit is about P Remove the excess and allow overnight drying. This is usually all you need to do to achieve an ultimately smooth finish, but you can repeat the procedure with a fourth coat, and with as many additional coats as Worthwhile rub down want.
Sanding an oil finish wet or even sanding dry between coats is risky if you have stained the wood. You might sand through some of the color, especially at edges.
Sand lightly and carefully. Film-building Finishes Film-building finishes include varnish, lacquer, shellac, water-based finish and two-part catalyzed finishes.
Varnish, on the other hand, requires overnight drying between coats. It stops up the pores and seals the wood.
It also leaves the wood feeling Worthwhile rub down, so you should Worthwhile rub down sand the sealer coat smooth. Varnish not including polyurethane varnish and lacquer are more difficult to sand than other finishes because they tend to gum up the sandpaper. Sanding sealer is varnish or lacquer with a soap-like lubricant included. Sanding sealer powders when sanded. If you are finishing a large project such as a set of cabinets with varnish or lacquer, it will be worthwhile to use a sanding sealer for your first coat.
The included soap weakens the moisture barrier and makes this layer softer than the finish itself.
Instead of using sanding sealer to gain easy sanding, you can thin the finish itself about half with the appropriate thinner mineral spirits for varnish or lacquer thinner for lacquer.
The thinner layer of finish hardens faster so it is easier to sand sooner. If you are finishing a wood with resinous knots such as pineor you are refinishing wood with silicone contamination it causes the finish to roll up in ridges or animal-urine or smoke odors, use shellac as the sealer coat. Shellac blocks off these problems but it is not easier to sand.
No matter what you use for the sealer coat, sand it after it dries using a grit sandpaper that creates smoothness efficiently without causing larger-than-necessary scratches — most often a grit between and P and P This is done easily using very fine-grit sandpaper: This sandpaper Worthwhile rub down the same soaplike Worthwhile rub down as sanding sealer and is usually available Worthwhile rub down auto-body supply stores.
Sand just enough so you can no longer feel the dust nibs. As long as you have allowed the finish to harden well so you can no longer smell any odor when you press your nose against itthe bag will level the nibs without damaging or changing the sheen of the finish. To create a more perfect and attractive surface, rub it with steel wool or gray Scotch-Brite. Rub in the direction of the grain. Rub the three or four inches nearest the ends using short strokes so you are less likely to rub over the edges and cut Worthwhile rub down.
Then rub the entire length, being careful to stop just short of the edges. You can achieve even better results by using a soap-and-water or mineral-oil lubricant with the steel wool or Scotch-Brite.
Oil causes the abrasive pad to scratch the least, but cutting will be slower and the gloss Worthwhile rub down higher. You can try one and then the other on the same surface to see which you like best.
Most professionals use soap and water. To achieve the ultimate rubbed finish you have to level the finish first and then rub it. Leveling and Rubbing Leveling a finish is a mechanical exercise employing the same exact procedure as sanding wood, with two differences: You use finer grits of sandpaper and you Worthwhile rub down a lubricant with the sandpaper to prevent clogging.
Here is the procedure. Using a flat sanding block to back your sandpaper, sand the surface until it is perfectly flat. Use a grit sandpaper that cuts through the flaws efficiently without creating larger-than-necessary scratches that then have to be sanded out, usually a grit between and P and P The oilier the lubricant, the slower the cutting and the less likely the sandpaper will clog.
I find that sandpaper clogs quickly with a water or soap-and-water lubricant, but you can use one of these also. Think in terms of four to seven.
In fact, you can sand in circles, which I find easier, and you can sand cross-grain near the ends to keep from sanding through the finish at the edges. Each time you advance to a finer grit sandpaper, change directions circles, with the grain, across the grain until you reach your finest grit which should go with the grain.
By Worthwhile rub down the sanding sludge with naphtha or mineral spirits, you will be able to see clearly when you have removed all the scratches from each previous grit sandpaper a big advantage over sanding wood. You will see your progress better if you use gloss finish rather than satin. After sanding a little, scrape off the sludge from parts of the surface using a plastic spreader. When the surface is an even satin sheen overall, it is level and you can move to a higher grit sandpaper to remove the coarser scratches.
Once the surface is level, sand or rub it with finer and finer grit abrasives until you achieve the sheen you want. Begin by sanding up to at least grit, continuing Worthwhile rub down back your sandpaper with a fl at block or a felt or sponge pad. Then rub with steel wool, or with pumice and a mineral-oil lubricant Worthwhile rub down a felt or cloth pad. If you want a higher gloss, sand up to grit P or higher and then rub with rottenstone and a mineral-oil lubricant using a felt or cloth pad.
Or use any other abrasive rubbing compound. A Final Word I find that woodworkers are often afraid of sanding a finish on a newly made project for fear of sanding through. This is sort of like the fear of sanding veneer the first time. You have to do it to learn that it takes a lot of sanding to actually sand through.