1. Backing: A flexible or semi-rigid backing (paper, cloth, film) to which the minerals are attached with adhesive. There is a designation for flexibility and durability ranging from A-weight (most flexible) to F-weight (least flexible).
2. Adhesive: Abrasives usually have two adhesive layers.
a. Make Coat--Initial layer of adhesive to anchor the mineral to the backing.
b. Size Coat--Secondary layer of adhesive to lock the mineral in place.
3. Minerals: There are five basic types of minerals:
a. Aluminum Oxide--brown or blue. Is the industry standard for metal, wood, composites, and plastics.
b. Silicon Carbide--black. Is used for sanding primers, sealers and paints, non-ferrous metals, and final finishing.
c. Ceramic Aluminum Oxide--A synthetic mineral that is very durable with an extremely uniform crystalline structure.
d. Alumina Zirconia--Primarily for heavy stock removal of metal and wood.
Abrasives sometimes load-up with dust before the mineral is actually worn-out.
1. Open vs Closed Coat: Open Coats have less minerals to create more space between abrasives to reduce loading, while Closed Coats have 100% mineral application with hardly any voids. Closed coats should have a longer life--as long as it does not load up with dust (a major problem with composite and woodworking abrasion).
2. Supersize Coat: There are some coatings applied to the abrasive that work as anti-loading agents ( 3M's FreCut )