While sanding supplies appear to be simple at first glance, choosing the proper sheets, belts or discs for your application can actually be fairly complex. You need to decide on the grit, the backer that will perform best, and even the type of abrasive used.
Should a body shop finishing a car choose a different type of abrasive than a woodworker sanding some moldings or someone restoring a fiberglass boat? We know that wood being sanded in preparation for paint should be sanded to a different level of grit than wood that will be stained. But should these choices of finish also help determine the abrasive mineral used as well?
The answer is that the abrasive that makes up your sandpaper will, in fact, affect the sheen of paints and top coats as well as the surfaces of unfinished materials. For example, Garnet is relatively soft compared to other abrasives and is often favored by furniture makers and restorers. Individual grains have few sharp points so stock removal is slower and can be controlled more effectively.
Aluminum Oxide is much harder and the particles tend to have very sharp edges, this type of abrasive removes material efficiently. The sharp points on the individual pieces will create well defined peaks and valleys in the scratch pattern when examined under a microscope. The sharp angles at the peaks and troths reflect light poorly making for a low sheen on the surface.
Silicon Carbide, on the other hand, tends toward less angular particles so the ridges are sharply pointed but the valleys are more curved. These rounded low spots reflect light in many directions creating a finish with more gloss. Steel wool, Non-Woven Abrasives and buffing compounds are often used as a final sanding finish reducing the sharpness of the peaks even more to increase reflection of light.
Rounding these sharp peaks can be done as wet sanding too, but this requires using sanding products fabricated to be used wet. This will often limit your abrasive material choices. Garnet, for example, is virtually never available in a wet/dry sandpaper.
We are interested to hear your experiences and preferences when it comes to how you choose the sandpaper, sanding belts, sanding disks, or sanding rolls for the types of work you do. Feel free to share with us on our Facebook page or via Twitter.