The Art of Sanding
by Jack Morse, Artistic-Turnings.com
Demonstrations for wood turning groups available.
Quite often I observe beautifully turned pieces on display, with a poor sanding job that stands out like a big red nose. In conversations I find that many consider sanding as a necessary drudgery that has to be done against their will. They haven't taken the time to learn how fast it can be done with the right approach. Most people start with too fine a grit of paper, and then sand and sand until they are tired and discouraged. One of the problems is that on most woods the scratches are white and blend in until the finish is applied and then they turn almost black.
A few do's and don'ts can go a long way in solving most problems:
•A - It seems natural that a faster speed would produce faster sanding, but in reality speed creates an air cushion that inhibits sanding, the slower speeds will sand faster. Speed builds up heat which will melt the bond between the grit and the paper, destroying the paper and imbedding the grit into the wood, further inhibiting the sanding. Some wood will stress crack from heat buildup and leave deep fine multiple cracks that won't sand out and you will have to recut the wood to eliminate them.
•B - Sandpaper is a cutting tool, it becomes dull with use, and unfortunately can't be resharpened. Wornout 220 grit sandpaper doesn't equal 320 or 400 grit sandpaper. "Use the sandpaper as if someone else was paying for it!" Good sandpaper is expensive but your labor is worth more. If you are able to do the job faster, with less effort, and end up with better finish, you will learn to throw away that worn out sandpaper!
•C - If you sand with the lathe running, put it on a slow speed and keep moving the sandpaper back and forth. Don't wrap it around the wood and hold it there, or you will end up with those ugly rings around the wood. Take the time to learn what the scratch marks produced by each grit of sand paper looks like!
•D - Stop often and inspect the work with a strong light at a 45 degree angle and look for light white marks. If you have problem scratches that won't come out, change the direction of the sanding to make sure you aren't creating them with buildup on the paper. Buildup on the sandpaper can be easily removed with coarser sandpaper lightly pulled across it.
•E - Most bowls are turned with the wood grain at a right angle to the lathe bed which means that 70% of what you are sanding is end grain. The end grain is more subject to tear out and damaged fibers, besides being harder to sand so extra effort is required. It’s not possible to do a thorough job of sanding with the lathe running and holding sandpaper against the wood, or power sanding with the lathe running. I prefer to sand the trouble spots first and then power sand with the lathe running to blend in any ridges I might have created while concentrating on individual spots.
•F - When I have sanded to the point that I am satisfied the job is done, I always apply a thin coat of lacquer sanding sealer and let it dry and further inspect the work. What is going to show up in the final finish will show up here, and it is much easier to sand the sanding sealer than anything else you could put on it. The sanding sealer will also harden up the fuzziness and enable them to be sanded off with little effort. If nothing shows up with the sanding sealer, a light hand sanding with 400 grit paper will finish the process, and you are ready to put on any finish you desire. Do not use steel wool or Scotch bright at this point for it will equally dull everything, It will look smooth, but there will still be ripples in it. If you wiped sanding sealer on or the excess off, you could have streaks in it that will show up again when you put the finish on. Hand sanding with 400 grit will sand off the high spots while the low spots will still be shiny until it is all sanded evenly.
•G - Quite often some tool marks won’t show up until you have sanded down to the finer grits of sandpaper and the last thing you want to do is go back to coarser sandpaper, so you sand and sand with that fine paper until you are tired and discouraged. You go ahead and apply the finish thinking it won’t show up. Well guess what, not only did it show up, it is worse than ever. You then leave it to the next day hoping it will look better then! The reality is that had you gone back to that coarser grit you would have finished in less time with a lot less aggravation.
Save time! Start with a coarser grit than you think you need and sand with it longer than you think you need to, until all tooling marks and damaged wood fibers have been removed, then the rest of the job will go quicker and be more satisfying.
Put as much pride in your sanding as you put in the rest of your project. A good sanding job will not be seen, but a poor sanding job will stand out above everything else.
A good sanding job looks like it hasn’t been sanded, where as a poor job is the first thing noticed. Think about it!