Part 2 of the silicon rubber mold-making series. Content restored — see the full mold-making guide.
Frequently Asked Questions
What does Part 2 of the silicon rubber mold making series cover? Part 2 of the silicon rubber mold making series covers the actual pouring process: mixing platinum-cure silicone correctly by weight, pouring technique including stream height and direction, filling to adequate coverage over the master, and cure times before demolding. It follows Part 1’s coverage of material selection, mold box construction, and master preparation.
How is silicone rubber mixed correctly for mold making? Both parts must be weighed on a digital gram scale using the manufacturer’s specified ratio — volume measurement is unreliable due to density differences between Part A and Part B. The components are stirred slowly for 3–5 minutes, scraping sides and bottom, then poured in a thin stream from a height of 12–18 inches to help air bubbles pop before the rubber reaches the master.
What is the pot life of most prop-grade silicones? Most prop-grade platinum-cure silicones have a pot life of 30–60 minutes at room temperature, but this is significantly shortened by elevated temperatures above 80°F. Heat can accelerate cure unpredictably, and residual catalyst contamination in reused mixing equipment can also shorten pot life. The full mold should be poured within the pot life window.
How long do platinum silicone molds take to cure before demolding? Most platinum silicones cure in 16–24 hours at room temperature. Demolding before full cure produces a weaker mold that tears more easily. The cured mold should be demolded by flexing the walls away from the master and working it free — not pulling straight — to protect both the mold and the master pattern.
Further Reading from Authoritative Sources
- platinum-cure silicone rubber — Wikipedia’s silicone rubber article covers the chemistry of platinum-cure systems including cure reactions, pot life factors, and inhibition that are directly relevant to Part 2 content.
- silicone mold making — Wikipedia’s Molding (process) article provides authoritative context on mold design principles and production techniques that the series guides are based on.