Questions about degassing silicone

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CharlesHouse

Active Member

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Luke0312

Sr Member
RPF PREMIUM MEMBER
You're putting the cart before the horse. You need to get a trial kit of something like oomoo and do some simple items with it first.

I buy the generic solo and dixie cups at the dollar store to mix in, the solo cups have the lines to measure (translucent cups are easier to use so that you can see the level).

Yes, you trash the cups after use.
 

Bigturc

Sr Member
RPF PREMIUM MEMBER
I reuse my smooth on measuring cup after I let it sit with the mixing stick inside. All the cured material pulls right out!! Resin mixing cup on the other hand are thrown away after each use to prevent introducing moisture in the mix!
 

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Burnate

New Member
I agree with Luke0312, try something that doesn't require vacuum degassing, why spend the money if you don't have to. I've used oomoo and mold star 16 from smooth-on and have had good success. If you check out their website it has a lot of useful information and instruction videos.
 

CharlesHouse

Active Member
I am using Mold Star for the mold, but I need something translucent for the prop I am building, and everything translucent is not low viscosity.
 

Burnate

New Member
Not sure if this will fit your needs but it is low viscosity:
PlatSil 73-15 Precision Silicone
A google search will take you to the web site, it's sold by Brick in the yard mold supply.
However a good degassing rig can come in handy, good luck!
 

cavx

Master Member
Given that chamber is small, then yes that 1.8CMF pump would be great. It should take it to -30" fast.

I bought a 3CMF pump for not a lot more, but really wish I had bought the 5CMF pump now due to the size of my chamber.

The only issue with a small chamber and pump is that you can only do small batches and that will be fine for most project anyway. I can mix several KG in mine, but I doubt that i will ever require that much for any of my projects.
 

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CharlesHouse

Active Member
Given that chamber is small, then yes that 1.8CMF pump would be great. It should take it to -30" fast.

I bought a 3CMF pump for not a lot more, but really wish I had bought the 5CMF pump now due to the size of my chamber.

The only issue with a small chamber and pump is that you can only do small batches and that will be fine for most project anyway. I can mix several KG in mine, but I doubt that i will ever require that much for any of my projects.

I wondered about the average size of a small to mid size object and how much silicone it would take to replicate. I am guessing I can tell by assembing the mold and filling it with water to measure the amount. f one pour is too small, can you make a second batch that dries at a later time than the first section, or would that make a line that is fragile?

What size chamber do you have now?
 

cavx

Master Member
I wondered about the average size of a small to mid size object and how much silicone it would take to replicate. I am guessing I can tell by assembing the mold and filling it with water to measure the amount. f one pour is too small, can you make a second batch that dries at a later time than the first section, or would that make a line that is fragile?

What size chamber do you have now?

My chamber (internal) is 500mm tall and 250mm dia. I wanted it to more than just vacuum silicone and elastomers and resin. I have also geared it up to reverse Vac Forming which is still a bit of work in progress.

Back to silicons, I have not used the vacuumable types yet, but from my work with elastomers, yes you can mix a 2nd batch and carefully add it to your first and not have a seam line. Generally it bonds seamlessly, even if the 1st batch has fully cured.

I have a 5KG bucket of vacuum-able silicone waiting a special project. Up until now, I have been using a quick cure (12min) additive silicone and the problem with not vacuuming the silicone is that you can trap small bubbles of air just under the surface. These may not affect your work or in my case, the may rupture and fill with the casting agent (in my case clear elastomer) and make small lumps on the surface ruining your work. And there is no real easy fix. The 10KG of this stuff I initially used is now pretty much a throw away.

So I hope the new vacuum-able stuff gives a much better result.
 
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