Silicon Carbide:

Color: Black

SIC is made by combining pure white silica sand and coke, a by-product of coal production.  Again, these materials are combined by melting in an electric furnace, crushing the results and sifting the particles through screens to get grit grading.  SIC grains are shaped like icicles with extremely sharp points and narrow grain bodies. It is second only to diamond in hardness; however it is very brittle due to the narrow grain body. Therefore when pressure is applied to the tip of this grain it fractures.  This characteristic is referred to as “friability”.  The benefit of friability is that a sharp edge is always against your workpiece providing extremely consistent finishing ability.  Because of the lack of grain body strength, which allows this grain to fracture with hand pressure only, the life as compared to A/O or the other grains is less.  This is why when you see SIC it’s normally in finishing type operations where the pressure required for working is lower than it would be in removal grits.  Examples of materials normally sanded or ground with SIC would include glass, plastic, rubber, paint varnish, lacquer & sealers. It may occasionally be seen in sanding on extremely soft woods like Ponderosa Pine, but we would recommend open coat A/O instead as the life would be much better.