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.