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You are watching: How to keep plaster of paris from sticking to mold

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Triple Ocarinist
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Hey guys,For those of you with mold making experience, Id like to know what works best for you in terms of release agents.Ive been using Vaseline for the past 7 molds Ive made- it does the trick, but not matter how sensitive you are, brush marks or fingerprints will still appear in the plaster afterwords and that INFURIATES ME
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Ive tried using oils but the lower half of my mold tends to just absorb it quickly and then when the top half is poured in, it bonds far too well to the bottom.Anything you can suggest that is non-toxic and food safe will be deeply appreciated guys! (ps- I dont want to use commercial mold release so keep it grocery or hardware store please
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Premium Poster
I have never done this, so I hereby declare that I am officially talking out of my arse - but how about that spray-on fat you use for frying?
Double Ocarinist x 5
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Premium Poster
Ill give the spray fat a try first. my only concern is that it will be just as thin as canola oil or olive oil, which just get quickly absorbed by the plaster.Plastic wrap wont conform perfectly to the fine shapes involved with one half of the ocarina no matter how you try- It would need to be vaccum sealed otherwise the plaster"s weight could shift the plastic wrap around, resulting in the wrinkly ocarina lolThe last thing I want is to be accused of ripping off Chen Chings ideas
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Pshhh, unless you let your ocarinas start looking like "molten lava" *cough*poop*cough*, you"ll never be accused of such :p
I have heard of using Murphy"s oil soap, tincture of green soap from Crystal soap company or even thinned dawn soap.My parents used to own a ceramics studio and they just allowed the clay to dry long enough for it to come out on its own. But they were plaster molds that you poured in a liquid type clay.
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Ahahahah! Achint, thats very true. I dont use slip casting...yet. So I don"t know of that"s work for me or not. I don"t need the release agent so much for the clay dud as much as I need it to separate the plaster halves when they"re finished drying. They always bond a tiny bit on some level and it takes me almost 40 min to separate the bloody things. But I will take note of that and see if soaps worked for anyone else on ze interwebs. Thanks penycat!


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I tried the cooking spray once. It seemed like a good idea, but it forms a lot of little bubbles and when the spray hits the surface. Those little bubbles left thicker rings of oil when they popped, and that texture transferred to the surface of the top mold. Not such a big deal where plaster meets plaster, but the bottom mold also contains the clay form of the ocarina. Since the spray covered that too, I ended up with ocarinas that where smooth on one side and textured on the other. I would spend a bit more time on those smoothing out the rough side. As a release agent, it really didn"t work any better than spreading on several coats of canola oil, which is what I still do. Yeah, breaking them open is a pain. I wait until they are really dry so the plaster doesn"t crumble so much, then I tap them around the outside of the seam with a chisel wedge and a hammer. You have to be patient and not drive the chisel into the plaster, but after a few minutes of going all the way around they usually pop apart. Occasionally, I"ve gotten too heavy handed with it and broke off the little bumps that had in there for keys, but I"ve never ruined a mold completely.I didn"t even know there was an actual release agent you could buy. I"m thinking it may be worth it.Soap, now there"s and idea. Thanks Penycat, I"ll try that next time.