Resin Addict Forum

I am very new to molding/casting, and have some questions about vacuum degassing. I've seen many videos of people degassing after mixing together parts A and B. They typically do this and then pour it slowly over the object they are molding. Some people have commented about degassing after the mold has been poured. What are your thoughts on this? Is this typical? Do you let it cure in the vacuum? Even after the silicon has settled it still seems to be raised more than when the vacuum is released. Would this effect the mold? Lastly I have thought about degassing A and B separately and then again after mixing. Is this beneficial, or would it be a waste of time.

Thank you! Again I'm super new to this, but very excited. I apologize if I haven't used all the correct terminology. Please correct me if I haven't, I want to learn.

Hi Rshill, welcome to RA!

It all comes down to how fast your silicone is curing. I degass my silicone after pouring into the mould box, because the silicone only has a 5 minute pot life. It's quite tricky degassing in the mould box though, as you have to make sure the expanding silicone doesn't overflow. After that degassing step I then leave the mould in a pressure chamber to cure for ultimate bubble prevention.

It's much easier to mix the silicone in a large container and then degas in that container, prior to pouring into the mould box. You would still want to lightly degas the silicone in the mould box though to ensure that there are no air pockets trapped in any undercuts.

Degassing A and B separately would be a waste of time, as the mixing process is where all of the air gets introduced.