Vaccum chamber question for silicone molds

[Capn_Jack_Savvy]

I create small Smooth On resin items and really need a vacuum chamber!! I am getting sick and tired of throwing out pieces because of freakin' air bubbles!

I see name brand vacuum chambers that run in the $500 to $1000 range. I came across Nalgene polycarbonate vacuum chambers that start at $150 sans pump. Has anyone tried using these for small castings? What pressure do you require for removing bubbles from resin or from silicone molds? Would this Nalgene system suffice?

Thanks in advance!!

 

[cavx]

Don't you actually want a pressure chamber to crush the bubbles down? From what I learned, the resin sets under pressure and can not expand once the pressure is reduced.

I bought a vacuum pump and built a chamber back in 2006 [ due to lots of misinformation] for exactly what you want to do. This did not work out well for me as apparently water boils under a vacuum at just 20 degrees C, so the resin was boiling and adding more bubbles than the vacuum could pull.

The research I did suggested that you also need Nitrogen to freeze the air and this lowers the temp.

The pump I had cost me about $600 and could pull 29Hg [units of Mercury] in about 11 seconds with the chamber I built [16" tall x 10" dia]. The 20mm Perspex lid would suck in and become hollow and the O-Ring would flatten out. I scared me a bit that one day the lid would implode.

Anyway, it was not working out for me so I sold it and now that I am getting into vac forming, wish I still had the pump.

 

[Zombie Killer]

You use the vacuum chamber to remove bubbles from the silicone or resin before pouring then you put the mold into the pressure chamber to compress and bubbles that are left into even smaller bubbles.

 

[Rebelscum]

You use the vacuum chamber to remove bubbles from the silicone or resin before pouring then you put the mold into the pressure chamber to compress and bubbles that are left into even smaller bubbles.

What he said.

 

[cavx]

You use the vacuum chamber to remove bubbles from the silicone or resin before pouring then you put the mold into the pressure chamber to compress and bubbles that are left into even smaller bubbles.

When you vacuum the resin, is that before or after the cat is mixed in?

 

[Rebelscum]

After. Though I personally never vacuum resin, except on crystal clear urethane. Even then, no often.

Putting it under pressure is generally all I ever need.