This video outlines the 2-part block mould making technique using Mold Star® 15 silicone rubber.
Mold Star® 15 is a platinum silicone that is mixed 1A:1B by volume (no weighing scale necessary).
When making a 2 piece mould, it is important to use the correct release agent to separate the 2 halves. When pouring silicone rubber, Ease Release 200 is the recommended release agent.
A 2 part mould allows for easier demould than a single piece cut mould or glove mould. It can also provide superior registration, reducing the amount of casting clean up necessary.