casting in humid conditions

[zerobmeister]

Hi there,

I live in Singapore and am keen to cast my own figures. I have a vacuum chamber setup that i inherited from a friend who's moved back to the UK, and am trying to cast my own sculptures using it.

However, when I activate it, I can't seem to get the chamber itself to evacuate right down to 30 inHg, which is what I need to get the cavities out of the resin I use (smoothon smoothcast 300). In fact, I can really only get it to get to about 26 inHg. We tried it with 2 different pumps, my quite small one and one massive industrial size, and only about a 40L chamber, so I can't see why the chamber won't reach the required level of vacuum.

Is it something to do with humidity? Can the pump not pull 30 inches in the kind of humidity we have here in singapore? Or maybe is there a defect in my chamber that's stopping it happening?

cheers

zerobmeister

[mangozac]

Hi zerobmeister!

Humidity won't effect the level of vacuum achieved. The only thing I know of that effects it is altitude, and I'm pretty sure there's nowhere in Singapore that high up to make a big enough difference!

40L is a fair chamber size. If you're sure that the pumps you've tried with are capable of reaching a high enough vacuum then you need to check for air leaks in the piping, lid seals, etc.

You'll never quite reach 30 inches of mercury (29.9 inches is full vacuum) and I would say in general anything over 29.0 inches is doing well. You might need to look at a vacuum + pressure technique...

[Anvils Hammer]

In my experience, even with a full vacuum (my kit can easily achieve 29.8) you will STILL get some air bubbles, I think this is due to the resin vapourising a littel inside the molds.

Anyways, if you vacuum then pressurise, it should solve the problem!

40L is massive!! It must take quite a while to empty that, whats the pot life of the resin?

AH

[Munkey Joe]