From: michaela440-AT-juno.com Date: Thu, 18 Mar 1999 08:18:32 -0600 Subject: Re: PUPT: NEOPREME problems I responded to Les privately regarding the neoprene problems, but I thought it might be good to share my two cents on this subject to the list. Here's what I wrote: Hi Les, If you use oil base clay.....when making a plaster mold, the plaster heats up (as I'm sure you know) which causes the oil from the clay to go into the pores of the plaster in spots. It's rare that it would affect the whole mold, but it will certainly do just what you described. Make thin spots here and there because the oil blocks the absortive quality of the plaster. And, yes, it's not really noticeable to the naked eye when examining the mold. Plaster molds for neoprene have to be absolutely free of oil (or other such contamination). The best way to prevent this is to keep oil from coming in contact with the mold in the first place. There's two realtively easy ways to do this that I know of: First of all, you can use a water base clay as has been suggested by others on the list. If you do that, you should still wash all the remnants and residue of the water base clay out best you can, before using the mold for casting neoprene. Second: If you want to work with oil base clay (some sculptors do not like working with water base clay; I'm one!) and not contaminate the mold, here's the secret! Seal the clay with a sanding sealer or other type of fast drying wood sealer. I know that sounds kind of peculiar but, you really can seal oil based clay with a wood sealer. It's like putting a coat of plastic over the clay. Use a fast drying spray sealer. Two to three light coats (don't want runs or sags) should suffice. I learned this little trick from a gentleman who is considered to be the foremost sculptor in the world, Blaine Gibson. He sculpted most all of the figures for Disneyland (Pirates of the Caribbean, Hall of Presidents, numerous animatronics, etc.), and all it's related theme parks. I had the rare privilege of meeting him about 20 years ago. I was able to pick his brain for quite awhile. A very gracious gentleman. In just a few minutes he solved several mold making problems I was having at the time (including making contamination free plaster molds for neoprene). Quite an experience. I'll never forget it. There are other ways to make contamination free plaster molds, but they are a little more involved. I'll tell you about that sometime if you'd like. Hope the above helps for now. Best regards, Mike Michael Brose Carlton, MN michaelA440-AT-juno.com --- Personal replies to: michaela440-AT-juno.com --- List replies to: puptcrit-AT-lists.village.virginia.edu --- Admin commands to: majordomo-AT-lists.village.virginia.edu
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