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 18 in. thick, use 15 drops per ounce of resin. If layer is 14 in. thick use eight drops per ounce. If layer is 12 in. thick, use six drops per ounce. If layer is 34 in. thick, use five drops per ounce. If layer is 1 to 1 12 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.