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Plaster mold release agent alternatives; something other than vaseline XD
Topic Started: 18 Feb 2012, 11:12 PM (30,209 Views)
OberonOcarinas
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~•Ocarina maker•~

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 :mad:

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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Jack Campin
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Opener of Catfood Tins

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?
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Kibbler
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Sick and tired
Would plastic wrap work?
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Jack Campin
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Opener of Catfood Tins

It would leave wrinkles.

Though a wrinkled ocarina could look interesting.
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OberonOcarinas
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~•Ocarina maker•~

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 lol

The last thing I want is to be accused of ripping off Chen Chings ideas :rofl:
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Achint
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Fat Mouse >^_^<

Pshhh, unless you let your ocarinas start looking like "molten lava" *cough*poop*cough*, you'll never be accused of such :p
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Penycat
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Ocarina lover at first site!
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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OberonOcarinas
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~•Ocarina maker•~

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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Hamlett
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Ocarina Maker and Seller

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.
Edited by Hamlett, 21 Feb 2012, 08:54 PM.
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Penycat
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Ocarina lover at first site!
Here is a thread with release agent info.

Potter.org
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CJ ocarinas
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Made of earth, Formed with water, Kilned in fire, and Sings with air

Oh wow thanks! That site has some helpful stuff!
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Robert Hickman
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Ocarina maker

Try applying multiple layers of oil, once the mold has set a thin sharp knife blade (i.e. plain Stanly knife blade without handle) may be placed over the parting line and tapped with a mallet. As long as there arn't any plaster runs, this method gets molds apart in a few minutes for me. Just be careful not to knock off the locator's in the process (yes, I have done that ;) ).

I believe that part of the difficulty in separating comes from the lack of paths for air to enter between the clay form and plaster.
Edited by Robert Hickman, 21 Feb 2012, 11:13 PM.
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Hamlett
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Ocarina Maker and Seller

Robert Hickman
21 Feb 2012, 11:12 PM
Try applying multiple layers of oil, once the mold has set a thin sharp knife blade (i.e. plain Stanly knife blade without handle) may be placed over the parting line and tapped with a mallet. As long as there arn't any plaster runs, this method gets molds apart in a few minutes for me. Just be careful not to knock off the locator's in the process (yes, I have done that ;) ).

I believe that part of the difficulty in separating comes from the lack of paths for air to enter between the clay form and plaster.
That's what I was trying to explain. I use a chisel wedge instead of a thin knife, but I have broken off the locator keys as well.
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OberonOcarinas
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~•Ocarina maker•~

I too have done that. As a precaution, I make 5 keys for my molds just in case one wants to be difficult lol

instead of hammering it open though I usually get a bundled up blanket or something dense but soft, set it on the ground and gently pound the mold on it while rotating along the seam. eventually it comes free and theres no damage, the down side is though, if the plaster isnt totally totally hard, little blanket marks get etched into the walls. Thats no big deal though as molds arent meant to be ultra pretty
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Kibbler
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Sick and tired
I mold the ocarina before it's dry. I use Vaseline to stop the plaster from sticking together, but I don't put it on the ocarina, if that helps you at all.
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spoonyspork
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L'il Tooter
I completely forgot about this thread, so when I went to make my first one I just grabbed the first thing I had on hand - Pam organic olive oil cooking spray. XD It did actually work well and didn't seem to want to soak into the plaster or clay. Maybe the propellants add a property normal oil doesn't have? The mold came right apart (REALLY surprised me actually... I gave a tiny tug to see what I might be working with and it just popped right off and I about fell over backwards!) but I probably just had beginner's luck or something. I did have the same problem as Hamlett - there are bubble marks on one side of my mold. Nothing a little smoothing doesn't fix :)
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geotjakra
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EpiCai Ocarina Maker
green soap: rubbing alcohol mixed with very little dishwashing soap, the soap is the separator, the alcohol makes it dry fast, this is what we all use in sculpture class.
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Lord Seg
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Resident Lurker, Future Overlord
I have no pottery or clay working background :nope: but I do bake (Pies, cakes, brownies, cookies :cookie: ) so I know a little bit about food safe release agents. When I read this my first thought was lard, it is obviously food safe and is the most effective thing I use to keep things from sticking to a pan. Hope this could help you. :D
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Jill
Beginner
I hope this ends up on the right page, never done one of these responses before. As a trained potter in a land that believes in 'make it yourself and make do' (New Zealand ) here is what we used to make a mould separator for plaster touching plaster. Also trained by Royal Worcesters head of mouldmaking in just that, making moulds - he used special mould makers soap but you can't buy that on the open market sooooo-
Paintbrush, water and regular laundry soap or any soap will do. Make a lather with the water and brush on the soap bar work into the surface gently but take time to get it worked into the surface of the plaster in a circular motion.
wash off with a little water and a damp sponge. do this at least 3x( one for each side and one for the middle)
Last time you add the soap do not wash off, leave there and dry wipe the surface smooth. Check no residue has built up in recesses along the edge of the item, if they have, work them out with a fine brush and little water, then dry off with a sponge or dry brush.
To open when completed, use a shock wave. - When the plaster has set, but before it goes bone dry and shrinks onto the item inside - place a flat metal item (washer works well), against the mould near the join line (Put it on the side you cast first)hold the mould in your hand or against your body and strike the washer with a heavy metal object (I use a lump hammer fro my big items)
Edited by Jill, 11 Sep 2017, 03:03 AM.
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