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Hello!
I am trying to make a large batch of masks. I was going to use latex/plaster as the mold (ie latex for undercuts supported by a plaster case for weight) but I'm not sure that the latex will survive making such a large number of masks. I have eliminated the undercuts as a result and am looking at using just plaster. I'm using Martin Favreau's quick release recipe. What I need to know is will the paper mache shrink (I hope so) enough for there to be the tiniest undercuts - ie scored lines to give the detail of teeth. Will that mean I have to wait longer before I can release the mask? I need to get these out and drying as fast as I can so any help is much appreciated!
Thanks,
Talulah
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That's a tough one! I just don't know if PM will shrink with plaster mixed in or not. I am thinking it won't, but that is just my guess.
If I were you, I would try one to see how it goes. It may be that your tiny undercuts may not be enough to cause the mold to grip the casting. But if it does, you'd best know with one.
Be aware that plaster first sets, then it cures, a chemical reaction, NOT a drying issue. After the plaster/PM sets, it would still be relatively fragile, but I would try removing it from the mold at that point, and then let it set quietly to finish curing.
If you can't remove it from the mold at this point, I don't think it is going to get any easier if you wait.
What kind of mold release will you be using?
Just out of curiosity, how many masks will you be making?
Sue
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Thank you so much Sue,
I have to make about fifty! They are big too - bigger than a human head. About 14 inches high. And I have to make some separate complete skulls - smaller though- as well! A bit of a daunting task. I have made batches of mix, all is at the ready but need to do this test - I think that is a good idea - thank you!
I wasn't sure about the mold release as I want the plaster to soak in as much of the liquid as possible. I was thinking maybe oil and then talc? Like a baking sheet. Not too much oil so that it still sucks in water... Or maybe a thin layer of acrylic varnish and then a layer of wet paper. Mostly the mask is very big, bold, clear shapes. Not much detail - its only round the teeth that there is the issue of the undercuts. It also has deep eye holes so I am terrified of it not coming out (or in one piece even) - maybe I should make the eye holes less deep.
Well there you go it is all a steep learning curve! I've used paper mache before but it was a while ago.
Thank you everyone for this website - it has been invaluable to me in my research and now even more so!
Talulah
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For the eyes, the depth is not as important as the angle. They can be a foot deep as long as the angle doesn't serve as an undercut.
I have made and used plaster molds, but I have never used plaster in a PM mix in a plaster mold. I am wary of like materials sticking to each other. Even one fingertip-sized spot sticking could be a real problem. But I don't really know if it IS a problem. Nothing ruins your day like not being able to separate a casting from the mold except with a hammer...
Murphy's Oil Soap (straight) is well known to casting artists. PAM cooking spray (rubbed to a thin coating), Vasoline/petroleum jelly rubbed on as a VERY thin coat. Some people have said they use WD-40 (but oh, does it stink!) but I am wary of the petroleum distillates in it.
From the ClayArt forum: "Dish soaps are your best bet I personally think. I use Dawn Dish Soap (concentrated). Thin it a little and brush it on at least 2-3 times, giving it 10 minutes to soak in between coats. After the last coat, rub it down to get rid of excess pooling. When your mold is taken off all you have to do is wash the soap away and your ready to use the mold once it's had time to dry out some."
The top release agent for potters is from Crystal, Inc. (Pennsylvania, I think). I've never seen it, but it may be referred to as Crystal Soap or tincture of green soap. But I've heard that it only comes in 40 lb buckets. If you know a potter, ask if they know about it, and if you could get a small amount. I once heard that you might be able to find a small bottle of it at a full-service drug store.
Their contact info: crystalsales@pmc-group.com or 800-525-3842
Sue
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Sue, you are an angel thank you! I think I'll go with the dish soap as I am in the UK and not sure that I'll be able to find a version of the crystal soap (though maybe it is the same stuff as sugar soap? I seem to remember that being used as a release on a course I did years ago. But it was for a plaster mold and then a filling of a weird mix of cement fibre glass matting and I can't remember what else - not very green.). If the dish soap doesn't work out I'll ring the number you gave and see if they can tell me the generic name or a uk equivalent (which is what I did for the kind of plaster to use in Martin's recipe).
Also thanks for the tip about the eyes - I was thinking I'd have to change it but hopefully it'll be fine - there is no undercut there.
Its just occurred to me how much space 50 slowly drying masks is going to take up - and me with a small boy running around the house too! fun fun fun!!!! Test piece tomorrow then hopefully straight into production.
thanks!
Talulah
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Your 50-mask drying problem brought back a very old memory, like 50 years!
I was just a kid and the neighbor was doing something for her son's school. It wasn't PM, I don't even remember what they were, but they were painted and there were a lot of them.
Think: clothesline.
Stretch a line across a room. Once the masks are firm enough to handle, run one end of the cord through one eye-hole of each mask to hang them up, and then separate them with clothespins between them to keep them separated so they dry properly.
Probably the higher, the better, both child-wise and heat-rising-wise.
Sue
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So you're using a mash??
Yes, it will shrink slightly with plaster (or ground chalk) mixed in. Don't use too much.
I think the talc idea might be best for release. You might try laying moist paper (no paste) in the mould, then a layer of pva followed by a layer of pulp. If your pulp is good, you should be able to put it between two plastic sheets and roll it thin. I can work mine down to 1-2mm. You can then spread it surprisingly smoothly and, because there is not much bulk, it dries quite quickly in reasonable warmth. For extra reinforcement, you can lay kraft paper on the inside, once the rest has dried.
If you want to talk any of this over, email me 'dopapier@aol.com' and we can arrange it.
DavidO (in the UK)
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Thank you so much,
After much experimenting I have decided to use a latex mold with plaster mother after all. Mainly as to get the required shrinkage I found I couldn't put in enough plaster to be able to get it to semi set quickly enough to get it out of the mold quickly. Also I was finding the release difficult. I have sealed the (mostly dry) clay with a thin layer of spray-on varnish.
I will definitely try rolling my mix between plastic - that sounds like a brilliant plan! Anything to thin out the mix and to make it smoother. A gleaming pate for my mask would be most satisfactory! If I have any problems with this I may well take you up on your kind offer and email for further advice - thank you!
Talulah
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You're welcome.
DavidO
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Rolling out the paper clay is brilliant - without that you'd never have a clue how thick it is at different points. The mix is working well and drying really strong. Hooray!
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