Possible to make mold of clay sculpt using alginate, then cast in liquid plastic?

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Egon Spengler

Master Member
I've searched but haven't found a specific answer to this question.
Is it possible to make mold of clay sculpt using alginate, then cast in liquid plastic?

I want to sculpt a mask form in WED clay and use alginate/alja-safe to make a mold of it. Then I was thinking of brushing on liquid plastic resin into the alginate/alja-safe mold. Will there be a lousy reaction or is it possible to do this? Thanks! :)
 

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pitchforknumb

Sr Member
I've done it several times. I've cast smoothcast 300 for this, and haven't had any problems. It's not something you want to use if you're looking to capture perfect detail, but more for if you're casting something to do some cleanup on, or refining.
 

pitchforknumb

Sr Member
Should work great. Just make the alginate as thick as possible. The worst thing is trying to cast something with thin alginate walls. Those thing will flop all over the place, and make life hell. Good luck, and make sure and post some pictures.
 

Mr Mold Maker

Master Member
The second you put alginate in water its already shrinking, so get your plastic in as quick as you can. Some urethane resins and plastics are moisture sensitive so I'd do a small test with some before jumping right to molding your sculpt.
 

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Egon Spengler

Master Member
Thanks! :) I'm actually thinking of using a more reusable material to make the mold from now, as I'd like to make several of the masks that I can look worn in several different ways. Any recommendations?
 

pitchforknumb

Sr Member
If you're going for multiple castings you can't beat silicone. It's pricey, but you're assure that whatever you're casting won't bond with it. I usually use Mold Max 30. If you want something that will last for a very long time, look for a platinum silicone, like there Rebound series, or Mold Star series.
 

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detenten

Active Member
I asked my Smooth On distributor about this, and he recommended against trying to cast resin in alginate, since the alginate will have water/moisture in it, and most resins will bubble up and react to the presence of any moisture.

That said, sounds like pitchforknumb did it just fine!
 

pitchforknumb

Sr Member
That said, sounds like pitchforknumb did it just fine!
It works. It's obviously not the best way to go about it. I use this method for making a junk mold of a sculpt, that I can then cast in resin so I can really smooth it down. I usually use Smooth Cast 300 for this. The quicker the resin sets up, the better the result will be. I also apply 3-4 layers of crystal clear, and do my best not to touch it, as it will peel off if you look at it wrong. You won't get all of the fine detail, but I wouldn't try this method for anything other than something you're trying to really sand down.
 

detenten

Active Member
You won't get all of the fine detail, but I wouldn't try this method for anything other than something you're trying to really sand down.

Yep, I think it'd work quite well with that application.
My project was a lifecast where I wanted minute detail, which is different.

Worst case scenario: you have to try again ;)
 

Dreddful

Well-Known Member
My experience in trying to cast resin in an alginate mold....nothing but problems. Caused severe warping due to the moisture in the alginate.
 

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Egon Spengler

Master Member
Thanks everyone! Yeah I decided to go with a latex mold and I'll be using Smooth Cast 305 for the final :)

I have the latex mold pretty well built up now and I just need to put a mother mold of plaster around it now to help keep it's shape. I was reading though that before doing that I should remove the latex from the sculpt and then put it back on and then make the mother mold? I'm concerned about doing that because of the way the sculpt is the latex goes pretty deep into some areas and I'm concerned I would not be able to put it back onto the sculpt properly? I'm probably over thinking it and over worrying. The tutorial I was reading says it makes it easier to separate the mold and mother mold from the sculpt once they are completed.

You can see the project I'm working on here. It's a Casey Jones mask.

http://www.therpf.com/f24/teenage-mutant-ninja-turtles-1990-casey-jones-208213/index3.html
 

pitchforknumb

Sr Member
No. Do not remove the latex first, before you apply your bandages. That will just introduce air between your core and the latex, and the latex won't conform perfectly to your core, and can cause warping issues when you apply the plaster bandages. If you release everything properly, it will take a little coaxing to get everything to come off properly.
 

Egon Spengler

Master Member
Just one more question, when the mother mold and latex mold are ready and I take it off, do I spray release into the latex mold before putting the urethane in?
 

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