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We learned to make jewelry from fine pewter from a book titled Principles of Centrifugal Rubber Mold Casting. But the book wasn't clear on how to open the rubber mold after vulcanization in preparation for channel cutting. What's the best way to do that?

It took us years to understand how to really do it, so I'm posting this as a self-answered question. Any additional answers are also welcome.

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  • Silicone oils will tolerate the melting temperature of tin. They will probably not affect the rubber but that depends on the composition of the rubber.
    – blacksmith37
    Commented Feb 2, 2022 at 15:22
  • To find materials in your location , search rubber mold release agents , or parting agents. When I searched many listing came up but specific information was needed.
    – blacksmith37
    Commented Feb 2, 2022 at 15:40
  • Talcum powder is used to prevent rubber sticking at ambient temperatures.; I expect it will work at higher temperatures. It should be easily available to try on your rubber molds.
    – blacksmith37
    Commented Feb 2, 2022 at 17:10

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In the video https://youtu.be/uOYkHcXCtzU, you see a craftswoman remove a mold from the vulcanizer, taking care to not burn herself. She places it on a work table and carefully inserts a large screwdriver to separate the two mold halves.

Vulcanizing the mold causes the halves to firmly stick together. Separating them requires a lot of prying power, like very forcefully inserting a large screwdriver.

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  • Thank you! Prying open the organic black rubber mold halves may be intuitive; still it is necessary to know that the artisan must be very forceful to insert the large screwdriver to separate the mold halves, because they firmly stick together, when the mold was vulcanized.
    – Maria Alaniz
    Commented Feb 2, 2022 at 2:09

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