Alc 40093 40 grit coal slag – 25 lbs. 25lbs extra-fine, 40 grit, .025″; 6.0 – 7.0 mohs; fast cutting, economical abrasive used to remove heavy rust scale or paint from steel and other hard materials; typically used in a pressure blaster or siphon blaster where the abrasive is not being recycled.; moisture resistant and does not pack which reduces clogging; has sharp angular edges and provides a high degree of etch for surface preparation and coating adhesion; note: the size of the blaster nozzle should be three to four times larger than the grit size of the abrasive being used, the larger the nozzle size, the more cfm of air is required