[Katherine Swift]

This question comes through email by Philip:

I have several flexible silicone molds, do I really need to use any mold release at all? I have a silicone spray that I have been using which is the least damaging to the silicone out of silicone spray, Vaseline or wax? am trying to cut costs, if you could recommend if any release agent is really necessary at all? and the best way to clean the silicone molds to prevent them from deterioration?

[Katherine Swift]

Hi Philip,

Great topic. When it comes to using a mold release with silicone molds, I compare it to wearing a seat belt when you are driving. You don’t need it very often, but when you need it, you NEED it. In general, if you are casting a well measured and mixed epoxy or polyester resin into a silicone mold, there is a very good chance things will be fine without a mold release. If, however, the resin is a gooey mess, the mold release may be only thing that allows you to clean it out of the mold. Here are a few more good reasons to use a mold release:

1. Silicones and polyurethanes don’t play well together. When I cast a polyurethane resin in a silicone mold, I always use a mold release.
2. If you are casting silicone into silicone, you must use a mold release, otherwise you will have one big block of silicone.
3. The more you pull on a mold, the more small microtears happen, which shortens the life of your mold. Mold releases minimize this from happening.

Out of the three mold release choices you gave me, I would bet the silicone spray is the best choice without seeing the ingredient list. Unfortunately, wax and vaseline (nor cooking spray) are good choices for mold release.

As for caring for silicone molds, we have an article about it on the blog that you may find helpful: https://resinobsession.com/molds-mold-making/5-tips-for-keeping-your-resin-silicone-molds-in-top-shape

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