SANDPAPER IS AN ABRASIVE, but not all abrasives are sandpaper. For example, there's steel wool, glass, pumice, and rotten stone-each product designed for a special smoothing job on wood, metal, plastic, glass, ceramic, or concrete.
Before you apply a finish on most projects or sometimes projects that won't be finished, you will often have to smooth the surface by sanding.

TYPES OF SANDPAPER
The term sandpaper is used to describe a variety of sheet abrasives. Among the most common are flint, garnet, emery, aluminum oxide, and silicon carbide. The abrasive particles may be mounted on paper or cloth, in open-coat or closed-coat density.

Flint. Flint is usually a light tan color. It has largely been replaced by other abrasive minerals.
Advantages:
• Least expensive sandpaper
• Open-coat paper is good for removing wax and paint finishes
Disadvantages:
• Very soft-wears down quickly Clogs easily
• Garnet. Garnet is usually reddish-brown in color. Advantages:
• Much harder than flint
• Particles fracture and create new cutting edges as the paper is used
• Good choice for woodworking a Moderate price Disadvantages:
• Not recommended for sanding metal

Emery. Emery, often bonded to a cloth backing, is recognized by its distinctive gray or black color.
Advantages:
• Extremely tough
• Widely used as a metal abrasive
• Moderate price
Disadvantages:
• Generates heat quickly
• Clogs easily (not good for woodworking)

Aluminum Oxide. Aluminum oxide is tan, white, or brown in color. It is perhaps the most popular sandpaper abrasive for fine woodworking and furniture finishing.
Advantages:
• Very hard mineral surface
• Tough and durable
• Works well for high-speed sanding
• Can be used on metal surfaces Disadvantages:
Can clog when sanding soft, resinous woods
Expensive (but lasts longer than other papers)

Silicon Carbide. Silicon carbide is distinctly bluish-black or greenish-black in color.
Advantages:
• Hardest, sharpest sandpaper available • Cuts extremely well
• Resists clogging
• Can be used to smooth many materials, including wood, metal, glass, stone, and plastic
• Suitable for wet sanding Disadvantages:
• Breaks down quickly when sanding harder metals
• Expensive

SANDPAPER CLASSIFICATIONS
Apart from the type of material that gives sandpaper its abrasive quality, there are other characteristics that affect performance. Finding the right combination of the following characteristics allows you to choose a paper for any job-from the roughest stripping to the most delicate finishing.

Grit. The grit-the size of particles that are glued to the backing material-are identified by distinct labeling systems (Fig. 1):
• Industrial system. This commonly used identification scale uses numbers from 16 (coarsest grit) through 600 (finest grit) to identify grit size.
• Old system. Identifies grit size with numbers that run from 4 (coarsest grit) to 10/0 (finest grit).
• Retail system. Describes grit size using word descriptions (coarse, medium, fine, etc.).

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