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Will Plaster Poured On Plaster Come Apart?


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if i took a hump mold i made with pottery plaster and poured new plaster over it, would the mold come out to make a slump mold?

 

 

Especially if you use a mold release. There are commercial preparations available on the market but one of the easiest and simplest is just plain ivory soap that is heaated to the melting point. Brush it on thinly, it washes off the plaster easily with hot water after you use it leaving no residue, and does not interfere with plasters ability to absorb water. Yes, I know that is very very old school :), the commercial preparations are very good.

 

Regards,

Charles

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Soap is a good release, but I've never heard of heating to the melting point--is this a bar of soap you are using, Charles? You might try going to your local drugstore/pharmacy and ask for Green Soap. Use it straight from the bottle and it, too, washes away. Hmm . . . this may be so old school that no drugstore carries it. It used to be the soap that surgeons scrubbed with before performing surgery. Good luck!

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I use Murphy's Soap also old school. I never heard of Charles system but it is intriguing and whatever works is good. I have used vaseline for casting off a glass lamp shade. It wouldn't release. A friend suggested heat lamps and it did release. I wrote an article for making hump molds for PMI. I have since played with just hanging a slump over and oval frame and let gravity create the slump with a little help from combing with a rib.

Marcia

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I use Murphy's Soap also old school. I never heard of Charles system but it is intriguing and whatever works is good. I have used vaseline for casting off a glass lamp shade. It wouldn't release. A friend suggested heat lamps and it did release. I wrote an article for making hump molds for PMI. I have since played with just hanging a slump over and oval frame and let gravity create the slump with a little help from combing with a rib.

Marcia

 

 

I suspect Murphy's soap would work well and it is simpler than melting bar soap. since Murphy's is water soluble it should clean up easily. I'll have to try it next time I make molds. I am in the process of doing a commission of several wall niches and one of the processes I used is from Marcia. I attached a picture of the green-ware slumped through the frame. the piece is 20" in the long axis. the niches will be be 48. The system works very well but to get the deeper slumps I've had to modify the process from simple combing. One of the things I really like about it is that you can mock up the actual installation. I only wanted to test the system but I hate to throw anything away. Once I start something I try to make a completed item from it. Soooo, this might not be the greatest looking item but it proved the technique and I liked the shape so I decided to finish it as a decorative bowl. Thanks Marcia.

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I use Murphy's Soap also old school. I never heard of Charles system but it is intriguing and whatever works is good. I have used vaseline for casting off a glass lamp shade. It wouldn't release. A friend suggested heat lamps and it did release. I wrote an article for making hump molds for PMI. I have since played with just hanging a slump over and oval frame and let gravity create the slump with a little help from combing with a rib.

Marcia

 

 

Let me try my photo again. You can see the form used at about the two o'clock postion. post-979-12972345681367_thumb.jpg this piece hasn't ben cleaned up yet either.

post-979-12972345681367_thumb.jpg

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I use Murphy's Soap also old school. I never heard of Charles system but it is intriguing and whatever works is good. I have used vaseline for casting off a glass lamp shade. It wouldn't release. A friend suggested heat lamps and it did release. I wrote an article for making hump molds for PMI. I have since played with just hanging a slump over and oval frame and let gravity create the slump with a little help from combing with a rib.

Marcia

 

 

Let me try my photo again. You can see the form used at about the two o'clock postion. post-979-12972345681367_thumb.jpg this piece hasn't ben cleaned up yet either.

 

 

Great Charles! That is how I make bird baths.

Marcia

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Sasha Wardell teaches plaster from plaster. My ceramic partner Lena took a course in the UK from Sasha and her molds are pristine. She uses a lathe to produce the original, then uses release mold soap to coat, wipe down, coat, wipe down, coat, wipe down. When she does the slump mold, the original plaster slips out faster than you can catch it.

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Sasha Wardell teaches plaster from plaster. My ceramic partner Lena took a course in the UK from Sasha and her molds are pristine. She uses a lathe to produce the original, then uses release mold soap to coat, wipe down, coat, wipe down, coat, wipe down. When she does the slump mold, the original plaster slips out faster than you can catch it.

 

 

My woodworking shop is a great adjunct to my pottery work and I turn a lot of models. In fact I like to turn simple models from softwood and then augment them with plasticine. The model is for one time use only so you can get away with a lot you couldn't under other circumstances. I use a compbination of bee's wax and mineral oil as a finish and I always use that for the wood eating ustensisl I make: its non-toxic and polishes to a high gloss.

 

Regards,

Charles

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