PlatSil 73-25 is a 1:1 mix platinum/addition-cure silicone that cures to a soft/mid-range hardness of A~25. This silicone is a blend of all the best properties available for a silicone mold rubber. PlatSil 73-25 is 1A:1B, by volume, so no scale is needed. The yellow colored Part A and green colored Part B make it easy to see when mixing is complete. A uniform, light, lime-green color means you're good to go! A mixed viscosity of 6,000 cP is easy to mix and pour and insures vacuum degassing is unnecessary. A 15 minute pour time coupled with a 4-5 hour demold time is the best of both worlds! PlatSil 73-25 does not shrink on cure and the resulting mold has great tear strength and easy release from all casting media.