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Hi guys.

I am mixing some two part plastic resin together with some talc filler and it is foaming up like cheap cola.

does anyone know whats going wrong??

Very likely moisture.

I haven't worked with talc in resins but have worked extensively with two part plastics. What is it you are trying to do? Also what is your mixing process, and at what point in the process are you getting the foaming problem?

Hi there. I am mixing parts A and B by equal by volume. eg, 10ml of each part plus adding 10ml by volume of talc.

the foaming is occurring just as the self heating starts. all chemicals and molds are kept warm and dry in the house.
sometimes it will foam and others not.

There are a couple of things you can do. First is that most of the bubbles are probably being generated when you stir the two parts together. This is tricky because you have to stir it to blend the two parts but getting to not foam is hard. I constantly fought this problem until I purchased a compression tank. For about $60 US I was able to get small compression tank. after pouring the resin you place it in the compression tank and pressurize it to about 60 PSI. This has the effect of crushing the bubbles as the external pressure increases. Higher PSI is even better but requires a more expensive tank. Most of the time it isn't needed. I now use this for all of my casts. The resin I use is Smooth On 310.

The only time my resins foam is because of moisture in the mix - excessive humidity is enough.

I use talc as a filler and have for a couple of decades now - also as my mould release agent - just a light dusting of it.