This is a special crushed and all natural black silica that has been selected and graded for its fineness and color. The top mesh sizes is 30 mesh, and it can be added into any of our plasters up to 10% by weight of dry materials or around 6% of premixed wet materials. The silica will be revealed most in thinner more polished finished, and should be added to plasters that have not been tinted or are tinted very light colors. The darker shades will not allow you to see the silica. Traditionally this additive is used primarily in raw un-tinted lime plasters and produces its own color and effect.