8 x 2lb Blocks Protolina Grey-Green sculpting medium. Non-Hardening, oil based sculpting medium. 16 lb case. This is a higher grade clay than standard Protolina. The Grey Green formula is much like a very soft Chavant. Like all of our sculpting clays (water and oil-based), Protolina Grey-Green is sulfur free so it can be used for Platinum silicone molds.