Sanding #1: Sanding

The first few times I picked up or looked at something a real professional, award winning woodworker made I marveled at one thing in particular – the finish. The most notable feature to me was an almost universal lack of sanding scratches, even in the fine detail.

There is an old adage that says “the finish goes on before the finish goes on”. This refers to surface preparation, sanding included. This series will hopefully shed some light on the techniques I’ve painstakingly tried to learn from some of the masters who were kind enough to help me.

Some woods can be polished to a high luster, almost glossy finish with no finish at all. Hard maple is one such example, bubinga is another. Others get wonderful sheens to them, hand planed pine is a soft wood that lends itself well to such surface finishing – with the right kind of plane.

Most woods can be finished more pleasingly with planes and scrapers than they can be with sandpaper. The reason for this is that sandpaper is an abrasive, whereas a plane is a bladed cutting tool. The sandpaper will actually abrade the grain, leaving a microscopically “fuzzy” surface that is smooth to the touch, but not the microscope. A hand plane shears the grain cleanly, leaving a sharply defined, very flat surface that reflects light. Probably the greatest reason that more woodworkers don’t use handplanes to finish surface their projects is that it is a difficult skill to learn, and a random orbit sander is so easy. One has to learn how to read the wood with handplanes, as all woods react differently to an iron. Some surfaces, like curly maple, are incredibly hard to hand plane, requiring smoothing planes with very high angled blades and cross grain cutting techniques. Other woods, like cherry, plane wonderfully with a simple old Stanley #5. This past weekend I showed my home builder brother just how fantastic a surface can be put on a piece of pine with a low angled plane – he was floored.

The results are well worth the trouble.

Another reason to avoid a hand plane for a finished surface is the choice of finish. Planed surfaces aren’t great for receiving stains and dyes. When I am to apply a dye to a surface I’ll plane it finish ready then go over it with 220 sandpaper prior to being dyed.

Sanding flat surfaces is no big deal, and a skill most woodworkers have mastered. A few hints might help a little here and there though, so here goes;

Use fresh sandpaper! I’ll repeat that it because it is the most important thing we need to know. Use fresh sandpaper! Use sandpaper like someone else is paying for it. Start with a grit lower than your first choice. If you wind up with sanding swirls after using your ROS (random orbit sander), go over the surface again, this time by hand, WITH the grain orientation. You’ll see those swirls disappear.

Wipe the surface off before starting on the next higher grit. The reason for this is that sanding grit comes loose from the backer during sanding, and coarse grit on the surface will scratch the surface as you go over it with the higher grit. Do this every time! Work your way up to the desired grit in this fashion and you will have a scratch, swirl free surface. When you’re done, consider going over the surface with a freshly tuned cabinet scraper, or some Liberon 0000 wool, depending on the look you’re after. You’ll likely be pleased. The steel wool will give it finish similar to that of a satin piano finish. The scraper will get it closer to that of a hand planed finish.

Liberon steel wool is the finest I’ve ever used. Some of the non metallic woven pads are also good for polishing the surface, WEB abrasives makes a synthetic steel wool that is pretty good, neat stuff. I like it because it won’t leave metal in the surface that might react with finishes or moisture over time.

Abranet is a product I’ve been using lately for sanding. It is a metallic screen with grit particles somehow attached to it. Truly marvelous stuff! It has replaced all of my standard ROS discs.

The next entry will deal with sanding round objects and discuss the use of Micro Mesh products. The entry after that will deal with sanding small, complex surfaces. I hope these blog entries turn out to be of some value.

-- Just another woodworker