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and now I need your advice. What is the best thing to put inside the mold so the papier-mache won't stick. I heard you can use Vaseline but it will make the piece greasy and it is hard to get off, I heard that you can use saran wrap, but I am having a hard time making it stay in place on the mold. I also heard that you can use tin foil, but I find the papier-mache sticks to it when I've tried to use it.
Does anyone have any advice on what the best thing to use with a plaster mold for the best release?
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Iv'e not tried the vaseline approach. I don't want the mess. I have tried the cling wrap, and yes it's difficult. You're gonna lose detail this way.
I've seen a suggestion to use lady's nylons. This method allows you to pop the paper out just by pulling on the nylon. However, I suspect that the glue will stick to the nylon, so this approach sounds questionable.
I've tried a couple layers of glue-less paper strips. Just wet these to have them cling to your mold, then follow with layers of glued paper. This works with limited success, but it's superior to the cling wrap method for preserving detail. However, I've used this on a ball to make a cup. A ball forms outward, not inward, so I don't know how it will work on a mold that's curved inward. Also, like the cling wrap, you're gonna lose at least some detail.
One thing I've seen for plaster, plastic, and clay slurry molds is Urethane Rubber. However, 1 lb of this is about $28 + shipping. Ouch. I can't experiment with that at that price. Silicone rubber is even more expensive!
That's about all I can offer up. If you find something that works really well, let us know.
Good luck!
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I have never had any major problems using vaseline/petroleum jelly. It helps preserve details in a way the other release agents I have tried don't.
I find that once the pm has dried the vaseline is fairly easy to wipe off with a cotton bud soaked in warm soapy water. If I am then slightly uneasy about the surface (ie will it take the paint, gesso etc I have planned) then I add a final layer of tissue paper pm. So far I have not experienced any lifting or bubbling, but that could just be luck.
Give it a go, the main thing is that you may end up throwing away the pm but the mould is usually fairly robust.
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Well...I`ve hesitated to post here because of the language barrier...but...I wont to tell that the best way to pop up something from the plaster mold is to use wet tissue paper for the first layer, and then use other papers and glue normally. This works with every kind of molds, not just the plaster ones, even for plasticine.
That`s it from me.
Ana
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Lengo: If I find anything that works really well for me, I'll be sure to let you know
newmodeller: How much vaseline/petroleum jelly do you recommend using? A thin layer, or should it be thinner than thin? Do you need to wipe out the plaster mold after you are done as well?
ana: Thank you for your answer. I think you do very well despite the language barrier. 
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I use only a thin layer applied with fingers and then a cotton bud in hard to reach crevices, The thing with Petroleum Jelly is that if forms a thin water resistant barrier. You just need to check that the whole surface is covered.
Personally I would try Ana's wet tissue suggestion first if you aren't keen on the cleaning.
Ana: I agree with with Len, you manage English extremely well.
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newmodeller: I don't have an tissue paper in the house, do you think that toilet paper would work the same?
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Yes, you can use toilet paper, but in that case spray the water on the paper in the mold, and go along gradually from edges to center. You can always use plain wet paper, I didn`t mention that because tisue is so thin and takes details easily. If you by something that is packed in tisue don`t throw it away, use it (like shoes, or a bag). Just be sure that every part of the mold is covered. Overlap, if there is some lifts after you remove it from the mold, just cover with PVA glue.
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No, I don't think toilet paper will work, used in the way described. It is too weak.
If anyone does manage to use it, I would be interested to hear their experiences.
DavidO
(lovely to see you in the Forum, Ana. You've been in the gallery of course quite a long time with your wonderful work.)
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DavidO, I did that with my mask, and it is working, just have to be careful with second layer.
Ana
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dopapier: I am trying it right now, so I'll let you know how it goes.
I did notice that the toilet paper was very weak when water was added to it, so I put the toilet paper into the mold and sprayed it with just enough water to get it wet from a spray bottle since I couldn't soak it in water and place it as you would regular paper.
After I put a few layers of toilet paper, I put a layer of paper without water on top to give it a little more strength.
I'll let you know how it goes when it dries.
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ana: Thank you so much for all your help! I really, really appreciate it. I have seen your gallery before and I love your work, you are very talented. <3
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One tip that I got from a concrete artists was to spray the inside of the mold with real shellac (not the synthetic kind). She said to apply five thin coats, letting dry about half an hour between each. She also said that if you try the brush-on kind, you will probably lose detail. And if you try fewer coats, it won't work well.
I have not tried this myself, but will be when I get my mold finished.
Sue
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