sandpaper

Sandpaper is a manufactured abrasive product consisting of abrasive grains attached to a backing material. It is used to smooth, shape, and finish surfaces by friction and is common in woodworking, metalworking, automotive bodywork, and DIY projects.

Abrasive grains come in several materials. Aluminum oxide is common for general-purpose woodworking and metalworking; silicon carbide is harder and sharper, suitable for hard surfaces and plastics; garnet is a natural abrasive still used on wood; ceramic grains are very hard and used for heavy-duty industrial work. Grains are held to the backing with resin or glue.

Backings include paper, cloth, and film. Paper backings are inexpensive and light; cloth or fabric backings offer durability for hand or power tools; film backings are rigid and resistant to tearing. Some sheets are waterproof or oil-resistant for use with lubricants. Bonds are typically resin- or latex-based.

Grit size is indicated by numbers; lower numbers are coarser. Common ranges include 40–60 (coarse), 80–120 (medium), 150–180 (fine), 220–320 (very fine), and 400–600 (extra fine). Higher microgrits (up to 2000) are used for polishing. Standards such as FEPA or ANSI are used to categorize grits.

Usage involves progressing from rough to fine grits to remove material and achieve a smooth finish. Wet sanding with water reduces dust and prevents clogging on some surfaces. Common tools include sanding blocks, sheets, or disc sanders.

History notes that abrasives have been used for centuries, but modern sandpaper with synthetic abrasives and standardized grit sizes emerged in the 19th and 20th centuries, enabling broader industrial use.