Structure and types of abrasive paper
Abrasive paper is used to smooth and finish surfaces of items made of metal, wood, stone and other materials. It consists of abrasive grains (crushed glass, sand and similar) glued onto cloth or paper. By grain size, the paper is numbered 12, 16, 20, 24, 36, 60, 80, 100, 120, 140, 170, 200, 280. The larger the number, the finer the grains: number 36 is coarse and number 200 is fine. One starts with coarse paper and then goes to finer ones, so the surface is smoothed step by step. When finishing, the paper should be wrapped firmly on a special wooden block; small parts are placed on paper fixed to a flat board and rubbed in different directions. Work makes dust, so a protective mask is worn and the room is aired.
Comparing grit: the teacher gives pieces of 2–3 grit numbers. The group compares how they feel (touch lightly) and arranges the numbers from coarse to fine. Do not rub the paper hard on your hand and do not breathe the dust; work with the teacher or with permission.