Russian Bentonite Foundry Equipment Specifiions. Canbensan Produces Drilling Bentonite Named As Canson Both OCMA Grade And API13A Grade Canson Is Naturally Ocurring Sodium Bentonite Mined From Specially Selected Ores Which Shows High Swelling Capacity When Added To Rotary Drilling Fluid Canson Improves Performance In Drilling Hole Cleaning And Hole Is Also Used To Seal And Plug The .