This is the hardening catalyst for use with Castin' Craft Clear Casting Resin . The catalyst MUST be combined with the casting resin for any hardening to take effect. The following is a guide to the recommended ratios for use of casting catalyst with clear casting resin: Formula for one layer: if layer is 1/8 in. thick, use 15 drops per ounce of resin. If layer is 1/4 in. thick use eight drops per ounce. If layer is 1/2 in. thick, use six drops per ounce. If layer is 3/4 in. thick, use five drops per ounce. If layer is 1 to 1-1/2 in. thick use 4 drops per ounce. For multi layer projects (especially when embedding items into it): first layer use five drops per ounce, for the second layer use four drops per ounce, for the third layer use three drops per ounce and for additional layers use two drops per ounce.