Smooth-On Moldstar 15 Silicone 2 lb kit with instructionsMold Star?? rubbers are easy to use platinum silicones which are mixed 1A:1B by volume (no weighing scale necessary). Mold Star?? silicones feature relatively low viscosities and vacuum degassing is not required for most applications. The pot life of Mold Star?? 15 SLOW is 50 minutes and cure time is 4 hours at room temperature. Mold Star?? 16 FAST is a faster material with a 6 minute pot life and 30 minute cure time. Mold Star?? 30 is a harder material, with a 30A Shore hardness.Mold Star?? silicones cure to soft, strong rubbers which are tear resistant and exhibit very low long term shrinkage. Molds made with Mold Star?? will last a long time in your mold library and are good for casting wax, gypsum, resins, concrete and other materials. Cured Mold Star?? rubber is heat resistant up to 450??F (232??C) and is suitable for casting low-temperature melt metal alloys. Note: THI-VEX?? is NOT compatible with Mold Star?? rubbers.