Abrasive is the substance used for grinding, polishing, or cleaning a surface. They come in different materials, shapes, roughness, and sizes. Hardest material being Black Silicon Carbide, which has a hardness second to that of diamond. Softest being Bicarbonate Soda, which has the same composition as your common table salt. Most durable being Steel Grit and Steel Shots. Some abrasive are recyclable and some are not. The most commonly used abrasives for cleaning purposes in sandblasting cabinets are Brown Aluminium Oxide and Glass Beads. The cheapest abrasives for yards and open blasting are Copper Slags and Garnets.
You must know what is the material you are working on and what sandblasting systems are you using to be able to get the best possible end results you are looking for. Sandblasting with the correct media will save you time and money.