by GPGarages » Thu Jul 21, 2016 8:16 pm
A quick caution regarding materials: As Dave has laid out, IF you are using the materials shown above, it will work fine. IF you are using another brand of silicone, be aware that if you use a platinum catalyst type, normal "hobby" clays contain varying amounts of sulphur and will inhibit the cure of such silicones. With the platinum (non-condensation) cure silicones, you must use a sulphur-free clay, commonly sold as "Klean Klay" here in the US, or any other sulphur free clay. An alternative is to COMPLETELY coat any clay surfaces with a wax or other sealant. In the distant past, condensation cure materials were not really suitable for mold making, as they cure form the outside in, and take a long time doing so, witness attempts to make molds using common silicone caulks, which are condensation cure. Obviously Alumilite (and likely others) have figured out new formulations which offer the best of both worlds, i.e., fast cures, good tear strengths, low shrinkage, compatibility with most any substrates, which previously were the exclusive realm of the platinum cure silicones, and low costs. Mold on!