I was wondering if anyone had some good advise for creating multiple piece molds from clay models. I'm looking for a process that's convenient - as these are just temporary molds. I've attempted to use tooling (Ultracal 30) plaster backed with hemp. I like the fact that plaster doesn't smell like most fiberglass resins, but it's heavy and bulky. I biggest issue I have with it is creating flanges for multiple piece molds. I wonder how they do it in design the studios. Any advise is greatly appreciated!
Post by Steve Austin on Apr 23, 2009 13:35:14 GMT -8
Basil, create the flange by inserting shim stock at the joint line and add a register every so many inches to locate each piece. The register can be just a piece of clay that you stick to the shim stock while the plaster is laid up. Once that side of the plaster is cured the shim stock is removed together with the clay registers and the next part of the mold is cast, use a release agent on the plaster face to help in dismantling.
Before stripping from the model drill bolt holes to lock the parts together. This will ensure integrity of the mold. If you prefer not to use shim stock build the joint face with clay instead and use the same registration sequence.
Thanks Steve - What do recommend in as far as building up the plaster mold? I've tried hemp, but it's very bulky, very random, and doesn't work well for forming up against the shim stock for a decent vertical flange wall. Your expertise is greatly appreciated!
OK Steve - I've decided to take things in a whole new direction. I am giving up on plaster molds due to the weight and apllication on vertical surfaces. What a pain in the rear! For that reason, I thing I am going to try an epoxy based system. Any suggestions on a simple way to prepped the clay prior to applying an epoxy surface coat and subsequent layers of cloth and laminating resin? Thanks...
Post by Steve Austin on Jul 22, 2009 6:51:36 GMT -8
I think if you're using fiberglass then coat the clay with shellac to form a hard coat. Several coats will give a good thickness then use regular paste wax and polish out. This gives you the first barrier of the release agent. Then apply a water based release agent Partall (www.freemansupply.com/PartallFilm10.htm) from Freeman Supply, see link. Once the Partall is dry apply paste wax and polish out again, this gives you several barriers of release giving you a good chance to save the clay.
You can also add another layer of Partall to the second wax coat for added precaution and apply another wax coat on top and polished out. You will find when the mold is broken from the clay the release agent should just peel out but like anything it's all in the preparation.