"Should I use mold release AND talc?" Topic

I just had a disaster with a new mold. I was able to save the master, but the mold was shot (more $$$ down the drain, so to speak).

So, I'm going to try again with a different rubber. I have used this combo with the resin masters and the Alumilite Quick-Set before, and it worked very well. But, I'm nervous now, and am wondering if I should/could also use a think layer of talc on top of the spray-on mold release?

Any thoughts?

Might be worth a try.

I know many manufacturers do that, and/or just use the talc.

What exactly happened with the mold on the first try?

Would it not let go of the master? Did it not cure?

The only time I ever had a problem with HSIII was with a wood master that had not been sealed. The first mold ripped apart, sticking to the master. I managed to clean the master and use a spray sealent on it, and the second try worked fine.

If the resin is porous or the the master has a very coarse surface, you may still have the same problem even with a different RTV.

I'm guessing as to what your problem was, but would probably consider sealing the master and use talc.

irishserb: The rubber stuck to the master, particularly on the sides. I was actually able to get some of it to demold, but the rest was just a clumpy mess.

I will take your advice, though, and make sure the masters are properly sealed. Then I will try again.

Mike

I talked to an individual who uses RTV/silicone, and he said he uses a can of spray primer to coat the mold/model (sorry, can't recall which – I think it is the mold), instead of a release agent.

He said it works great.

Some of the primer may stick to the resin after casting/curing, but that is fairly easy to remove.

Make sure to let the mold fully cure, before trying to remove the model from it.

Curing time will depend upon the mold material used, temperature, humidity, etc.

I would recommend a 24 hour cure, at least initially, just to be safe.

I use both. On my first mold I did not use enough talc, and the mold was nearly ruined (along with $1,000 USD of original sculptures). Since then I liberally apply talc to both sides of the mold after spraying them with release.