Woodturners use sandpaper to bring the surface of a turned piece into a shaper for final finishing. In some cases, very fine sandpaper may be used to complete the finish itself, particularly if a lacquer finish has been applied. It helps to understand what sandpaper is in order to use it well.
Sandpaper has been used for surface preparation at least since the thirteenth century when the Chinese recorded that various materials had been glued to parchment using natural adhesives so as to refine the surfaces of prepared objects. Some people had already used the natural abrasive qualities of certain plants as well as rough shark skin in the same fashion. Today it belongs to a family of coated abrasives which consist of various materials such as aluminum oxide bonded to materials like paper or cloth.
Sand and glass were the earliest materials to be used for this purpose, thus leaving glasspaper and sandpaper as generic names for the abrasives even though glass or sand are seldom used today except on the cheapest of products. Woodturners and other woodworkers should avoid them at all costs. Buying them is a false economy.
Most woodturners will use sandpaper with a paper backing although mylar is often used for extremely high grits. Select a paper that allows for easily contouring to the curves of a turned object. The finer grits above three or four hundred will generally have a very flexible mylar backing and waterproof resins that allow for wet or dry sanding although woodturners will generally be sanding dry.
While there are a variety of materials used for sanding, woodturners, and for that matter woodworkers of all types generally use only three. Garnet is a favorite of woodworkers and is often used in grits up to three hundred. Aluminum oxide tends to be more expensive but last longer under high heat conditions which may sometimes be found in finishing woodturning and is often found up to four hundred grit. Silicon carbide is also long-lasting but again more expensive and woodturners generally use it for grits six hundred and above. Most of the time it is found in wet or dry paper and is often purchased from auto supply stores where it is sold for sanding finish coats of lacquer.
Grits leave a better surface the higher the number but it makes no sense to start with too high a grit as it takes a long time to sand out any irregularities and scratches in the beginning surface. Coarse grits have a lower number and remove material faster but leave scratches that must be removed with the next higher grit leaving smaller scratches and so on.
Regardless of the material found in the sandpaper, a proper sanding job will leave a surface that a good finish will make shine. However, that finish is only as good as the surface it goes on. Taking time to understand and use sandpaper well will give a woodturner a project to be proud of.