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Anyoone know the best release agent for removing papier mashe from a plaster
mould? Any help appreciated.
Have you sealed the plaster mould Sarah?
If not, it will help a great deal. You can then use Vaseline (a very thin smear) or cooking oil.
There is also the dry paper method, where you lay unpasted strips for your first layer. The danger is though, that some of the paste might seep through the dry layer. I personally have never got on very well with this method; especially when using a detailed mould as it not only stops pasted paper getting into all the nooks and crannies, but in pressing down into the mould to form the shape, you are effectively squeezing the glue to the dry paper.
Murphy's Oil Soap is used by many PMers, but I don't know if it is available in GB. It's used on wood furniture and horse tack. It comes in two forms, the condensed version with the screw top, and the diluted version in the spray bottle. Use the condensed type full-strength. Just use a piece of sponge and spread it over the plaster.
I don't believe you need to seal the plaster with this, as the 'raw' plaster will absorb some moisture (a good thing), but it won't get wet enough to soften the plaster (which is more difficult than people imagine).
I have used Vasoline (petroleum jelly), but ran into an issue with the paint not sticking in some places. I probably applied it too thickly, though.
Whatever you use, use it sparingly.
Jackie mentioned the dry paper method; I've never used that. I've used a wet-paper method, where you press one or two layers of moistened (w/o glue) paper, not sopping wet, into or onto the mold, and then start applying paper that has glue applied.
But there can be the issue that Jackie mentioned, of glue seeping through the moist layer and attaching to the mold, but it isn't too much of a problem AS LONG AS YOU DON'T OVER-APPLY THE GLUE. Way too many people think that more glue, or thicker glue, is better, and it isn't. Don't dip the paper into the glue, apply it lightly with a brush, then press into the mold.
One good thing about papier mache is that it's cheap to experiment with, and easy to discard the poor results. I work with concrete, too, and bad jobs are far more difficult to dispose of... usually a hole in the ground.
Update: The company that produces Murphy's Oil Soap responded to my email, and said that it is only for sale in the U.S. and Canada.
But I did a Google search for just "oil soap Britain" and came up with some olive oil and coconut oil soaps, and maybe they would do as well.
I've never used plaster molds to do PM casting, but when I do make molds (usually made from hot glue or home-made clays/doughs), I use mineral oil as my release agent. I apply a thin layer to both halves of the mold with a paint brush. The PM absorbs a little bit of the oil, but I've never experienced any problems because of that--paint still adheres to it fine afterwards, etc.
Oh yeah, I should also note that I don't do hollow castings with layered strips, mine are solid casts. I mix tissue paper and glue together, to create what I like to call "Kleenex Putty", which functions like sticky clay--while that works fine for me, that's probably not terribly practical for larger projects.
Here's an example of molds/casts for spider legs, that I made back in 2010:
Last edited by Patraw (2014-08-07 16:07:40)
I have only read about it, but never used it. It is made from seaweed and originally used for dental and prosthetic castings/molds, and is one of the few materials that is safe to use directly on skin. The Jacquard name brand costs about $4 per (dry) ounce, but some craft brands are much less expensive.
I make a release agent from paraffin and kerosene. that is greaseless, and won't interfere with finishing. I apply this to plaster molds that have been sealed with dilute orange shellack.
To make the release, shave or grate a block of paraffin & place the shavings in a glass jar. Pour in enough kerosene to cover the shavings. Place a tight lid on the jar & set it down into a container of hot water, enough hot water to reach the same level as the kerosene. Take the jar out and shake it now and then. When all of the paraffin has dissolved into the kerosene the release is ready to apply. For a new mold, apply this while still warm, using a chip brush. Let the mold sit awhile, 15-30 minutes, then polish out with a cloth. You may need to repeat the application if the mold absorbs the first coat.
That's certainly a new one for me, Jim! Thanks a lot!
Did you ever find any sources or answers for the paper you were trying to find?
Thanks, Sue. I use the same release agent for all of my mold-making, as well.
The paper search continues. I have been sending samples of the old papers to distributers and mills in my area, but not much luck so far. In terms of substitutes I have been trying to work with Cosmo Blotter, and will be trying out Arches Cover and Zerkall Copperplate. All of these papers are minimally sized, but they are far more expensive than the papers I had been using.
Jim, I have reading a book (Playing with Paper) by paper artist Helen Hiebert, and I wonder if she could help provide a source for your paper. She has studied and worked with paper in Germany, Japan and the U.S.
She has a contact option at her website, and if she can't point you toward the exact solution, maybe she could suggest something suitably similar. Just an idea.
Thanks, Sue. I will try to catch up with this lead soon. Early on in my search I contacted Dieu Donne Papermill,
www.dieudonne.org. They teach paper-making and maintain a "Paper Library" of samples, unfortunately they
couldn't provide much help.
There are several people who contribute on this site who really know what they are talking about. We haven't had many posts from Jim Seffens, but he has a lot of experience and has been willing to share it. He has a gallery on this site and it is worth following the link to his website, which has interesting work as well as being a good design in its own right.
Yes, Jim does beautiful work! Good proportions and finishes, a couple of the most difficult parts to get right.
I couldn't get to his home page via his link in the gallery, so you can find it here: http://jimseffens.com/html/index.html
Thanks so much for the kind comments!
There is a little film clip on my website that shows antique papier-mache toys, and a film montage of me making a toy. It's easy to miss, since the link isn't obvious, but click on the brown box with my name in it below my bio if you'd like to see a speeded up version of my mold-forming process.