Precision is mandatory. Platinum-cure silicones rely on strict 1:1 by weight curing time and ratios rather than volumetric spoons. Even a 5% variance in Part B catalyst can leave the center permanently uncrosslinked.
First, weigh equal parts of Part A and Part B into separate disposable polypropylene mixing cups using a digital gram scale calibrated to 0.1g increments. If adding color, tint Part A before blending. Standard water-based acrylics or alcohol inks will destroy the chemical reaction. Instead, mix micro-drops of specialized silicone pigment dyes or oil-soluble concentrates, which integrate seamlessly into the polymer chains without compromising transparency.
Stir the combined mixture slowly for 3 to 4 minutes, continually scraping the interior walls and flat bottom of the cup to prevent unblended pockets. High-speed mixing whips air into the formula. If you lack a vacuum degassing chamber, hold your cup 12 to 18 inches above your silicone molds and pour the material down in a hair-thin stream. This stretching action snaps macro air bubbles before they settle into mold crevices.
Allow the mold to sit completely level at an ambient temperature between 70°F and 77°F. Colder work areas can double or triple curing duration, while excessive ambient humidity risks bubbling the silicone's exposed surface.
