Stupid maybe.. Silicon Mould release?

ManicMan

Lord
well, not really what I would call mould release.. normally when I think about that, I think of what you put on the mould so you can get the cast out easier (with Resin in Silicone, I don't use anything, with Metal in Silicone or rubber, I use a fine chalk powder) but I'm trying a couple of new methods of doing 2 part moulds where 'cast in one block and cut it in half (mostly) isn't really gonna be that easy.

so far, I've been mixing up a small amount of silicone as a bed, then placing the models and spur and stuff on top of this layer. Then pour a very small amount of silicon which basically just builds up the rest of the one half of the mould. then you end up with half of the mould created, and just need to pour the second half. Of course, the problem is that second layer. while I would say not 100% as strong as a single (or atleast when still liquid) pour, pouring silicone onto cured silicone will still set. So you really need some release material to reduce that greatly.

Looking around, short of getting some specialist stuff (though often I do debate how well such things work.. I got some specialist airbrush cleaner and my Iso does a FAR better job.. good thing I was a small-ish bottle, but it was still probably more then the iso cost (generic 99% isopropyl alcohol vs Army Painter airbrush cleaner.. alcohol really wins on both price and effectiveness).

I see a few ideas of stuff.. I did use to try painting on a thin cloth of Vaseline but that isn't fantastic (mostly trying to get a thin smooth coat). Some people have said a mix of 70% iso with 30% of either soap, Dishwasher soap thing, or vegetable oil (for some reason) which can be sprayed but.. I would have thought just using one of them pure would probebly do the same thing.. but I'm not sure how good or bad either would be. I'm not sure about iso and silicone.. doesn't 100% sound like a great mix to me. Probebly fine though.

of course, I guess the Chalk powder might also be a possible idea. puff some of that on the silicone might do a nice job..

anyone got any nice experience or ideas?
 
Fully cured silicone will peel off fresh silicone. Leave the initial pour over 48 hours in a decent temperature and you should find the second pour doesn't stick to it. Vaseline and wax release agents can be used to create a barrier, but they always add thickness to a mould seam which prevents absolutely accurate reproduction. If I make a multi-part silicone mould I just wait a few days in between, never had a problem.
 
That's really useful to know, I rather gave up on double pour two part moulds some years back because I never got them to work that well, evidently patience may have been the key! More recently I've just done a single pour and cut the resulting lump! However it's a bit more prone to catching an air bubble I find.
 
mm.. I probably didn't leave it long enough.. felt cured.. I use well.. I think they call it fast cure but It still takes a day or so, I'll be leaving this last bit a few days as I'm kinda out of silicone I like to use.

I have no problems with air bubbles with the stuff I use. I was looking at one different type cause they said it was a reusable silicone where you could just cut it up, heat it on a cooker and it melts. Then you pour it as if new and it'll allow about 38 re-uses.. but then I didn't like the price being fair higher then what I normally use, was a bit unsure what temp it might need cause if too high, it's gonna be interesting depending on what I'm making a mould from, and its either gonna need a high temp, Or it would melt at a low temp, so useless for any metal casting. Even low melting point metal still needs 350c or so.

But if just giving it a bit more time for it to properly cure then it should peal would be great ^_^ Guess I'll find out next week.
 
You can dissolve vaseline in real turpentine (not turps/white spirit). Brushed on this gives a very thin layer which silicone will not stick to, much thinner than vaseline alone. Leave it an hour or so for the spirit to evaporate before pouring new silicone over it.
Smells like real art too!

I have never found a re-usable silicone that will stand white metal casting temperatures (some won't even survive the heat resin curation generates) although they are excellent for casting Hydrocal or other high density plasters (Jesmonite being the best) for scenery.
 
yep. that silicone did seam.. weird and a bit pointless. Though did get me thinking about what the melting temp of silicone is.. I know it's pretty high (ish)..

oh and yep.. Don't try this at home kiddies.
 
I think you might mean gelflex/vinamold/hot melt vinyl? I use it with the students when they only want a single cast of a large object as that can be way too expensive with silicone. It's good stuff, but easily ripped and very prone to moisture. Plus your original has to withstand 200 degrees.
 
might be. Hot melt vinyl? mm.. that I have heard of before.

I kinda like the idea cause sometimes, I just don't use a mold that many times so it's kinda... annoying (taking up space and a bit of a waste) so ways to recycle them are always good, but the temp does appear to be pretty low. Does sound good for students though. Depending on the Silicone, the stuff isn't the cheapest around so large objects are a problem.

Have wondered about how easy it would be to shred old silicone as filler but getting it small enough and making such it doesn't get too close the model has kinda made me unsure and not tried much.
 
Have wondered about how easy it would be to shred old silicone as filler but getting it small enough and making such it doesn't get too close the model has kinda made me unsure and not tried much.
I know several modern "flats" manufacturers that do that for the core bulk of their moulds. Most of their runs are limited edition so I guess it makes sense economically.
 
Have wondered about how easy it would be to shred old silicone as filler but getting it small enough and making such it doesn't get too close the model has kinda made me unsure and not tried much.
Shredding rubber as a filler in big block moulds works very well. I like to bounce it around with a bit of acetone to ensure it bonds with fresh silicone (acetone makes the surface of cured silicone 'sticky'). If you have thin mould walls though you are better off avoiding it.
 
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