Pressure Pot Moisture?

[gwhesser]

I'm new to casting, but have gotten some OK blanks so far. I just bought a HF pressure pot to eliminate bubbles for tube-in casting.

Here's the deal: I'm using Silmar 41, 3 drops per ounce of catalyst, air conditioned environment set at 72 degrees F, no coloring added, pressure set at 50 psi. I left the casting in the pot for 24 hours, after which time my left over resin (control) had solidified. But when I opened the pot the resin was still liquid. Needless to say, bubbles galore formed immediately; AND the casting still took 2 more days out of the pot to solidify.

So - does the air from my compressor maybe contain too much moisture? If so, what to do about it?

 

[Leviblue]

Doesn't sound like moisture to me. When I had moisture in the resin it turned milky in color. To remove moisture from the compressor, use an inline moisture filter/drier just before the pot.
This sounds more like not enough catalyst or a bad batch. IMHO

 

[Sylvanite]

I find that when I cast polyester resin in a pressure pot, I need more warmth for the resin to kick. I sometimes set the pot outside in the sun and that seems to do the trick.

Regards,
Eric

 

[gwhesser]

Thanks for the input. I did another batch exactly the same, but left it in the pot for 48 hours. This time it came out harder, but still not where it should be. Next batch I'll add 1 more drop of catalyst per ounce and also get the pot a little warmer. My comfortable AC may be working against me.

 

[Brooks803]

Another option would be to heat the resin in a water bath. It speed up the curing time. That also means you gotta be fast getting it under pressure but atleast it should harden all the way.