You’d think choosing sandpaper would be a no-brainer—there’s coarse, medium, and fine, and that’s about it, right? Wrong: There’s aluminum oxide paper, silicon carbide paper, garnet paper, even ceramic paper. There’s paper you use dry, paper you use wet, paper you use on wood, on metal, and on finishes. There’s paper you use … well, you get the idea. Then there are some abrasives that aren’t paper at all. Here’s the least you need to know.
Aluminum oxide (the brown paper) is a good, all-around sandpaper and what most people reach for. It’s particularly good for sanding wood, because the relatively soft aluminum oxide particles fracture as you sand, exposing new, sharp edges that make the paper keep cutting longer. But if you’re sanding something harder than wood—varnish or paint, for instance, or metal—a harder abrasive like silicon carbide (gray or black paper) will last longer. The folks at 3M recommend their silicon carbide paper specifically for varnish stripping. (Some silicon carbide sandpapers can be used wet to reduce clogging; that’s more like polishing than sanding, not what you want when stripping off finish.)
Garnet paper (reddish) is soft and gentle for fine-sanding wood, popular among cabinetmakers but not so good for removing a finish. Ceramic paper is aggressive, and will take off the finish and the underlying wood if you’re not careful. It’s mostly used in belt-sander and other heavy-duty work, not something you want to use on brightwork.
But hey, you don’t have to use paper at all. 3M makes not only a wide variety of sandpapers, but also Scotch-Brite nylon/polyester pads with either silicon carbide or aluminum oxide abrasive, in a variety of “grits.” Many expert refinishers use Scotch-Brite pads in place of sandpaper, especially between coats of finish. The pads can be used wet or dry, and do a heckuva job at scrubbing pots and pans, too!