Product Description of the Red Nitro Ceramic Flap Discs, 10/Pack
Ceramic is in some cases supplied with a “topsize” (also known as “top coat”, or “supersize layer”.) This is a coating which is sprayed on to the grit to act as a coolant when working on heat-sensitive metals such as stainless steel and exotic alloys, and therefore reduce discoloration or burning. It can however also act as a lubricant to help reduce loading (where stock removed from the workpiece builds up on the abrasive and makes it less effective) on softer metals such as aluminium. The presence of a topsize does reduce the aggressiveness of the grain however, and so it is best not to have one if discoloration will not be an issue, for example when working on mild/carbon or structural steel.