What are some of the physical properties of sandpaper?

Answer 1

Aluminum Oxide is one of the most common woodworking abrasives. It exhibits a high degree of friability. This means that when heat and pressure are applied it fragments. This is highly desirable because when Aluminum Oxide fragments it creates new sharp edges. This self-renewing property allows aluminum Oxide to last longer than most other sandpapers.

Garnet is a natural abrasive that is still commonly used in woodworking. It is not friable like Aluminum Oxide and tends to wear out a lot faster. This is not necessarily a detriment since garnet will produce a smoother surface than aluminum oxide of the same grit number. It will however cut slower than its stronger cousin will. Garnet is also an excellent choice for a final sanding paper. It has the tendency to burnish, or seal off a wood's grain. This allows pigmented stains to penetrate woods such as birch, pine, or lauan, more evenly.

Silicon Carbide is harder than both Aluminum Oxide and Garnet. This makes it suitable for cutting harder materials such as metal, paint, plastic, and fiberglass. Silicon carbide is also a friable abrasive but wood is not hard enough of a material to fracture its surface so it will tend to wear out faster than Aluminum Oxide.

Ceramic is not a friable material. It is the hardest of all of the abrasives commonly available. It is generally available in only the roughest grades for fast wood removal in woodworking. The most common use for ceramic sandpaper is shaping and leveling of wood. It is also one of the most expensive materials available. You are most likely to see ceramic abrasives used on belt sander belts.

Answer 2

Sandpaper is a rough, coarse material. Harsh on the skin.