I need some serious help!

Hello, I have made a skull sculpture with the lower jaw attached and the mouth wide open, the skull is about 8 inches in diameter.

My questions are: 1. Should I use latex for the mold? 2. Where would I slit the latex to release the casting? 3. How would I make the support mold to fit around the severe undercuts?

These may seem simple to you - but I just can't grasp this situation - I can make art I just can't reproduce it!

Thanks for you help! Jeff

Jeff- I don't use latex rubber much anymore but it has some advantages, mainly how tough and stretchable it is. You basically 'plant' (glue or fasten down somehow) the item on a plank with the surface which will become the pouring hole touching the plank. Then by painting, dipping or spraying the latex once or twice a day, you build up the mold, including a collar on the plank. Latex molds must not be slit, just peeled off like a sweater. Support molds are made in multiple pieces and the interior of the mouth might be a single or several pieces, placed in the latex and not attached to the (typically) 2-halves of the main support mold. The latex mfgr. I used said, fill the undercut area with clay and make the main mother mold, then remove that clay. They knew that minor undercuts were stiff enough to not collapse when the mold was filled. True or not? Not if the undercut is big! I prefer using latex foam rubber (upholstery shops have scraps) to fiit my voids and just paint it in. This is squeezable so it can yank out of tough places. It is perfectly reasonable to make changes in a sculpture so that it is releasable from a mold.

This is a tough question to answer in words alone:

If you have very little experience in moldmaking, I recommned highly that you hire a professional and then sit in and observe how its done.

The openning between the teeth has to become a 'separation plane'- that is, the rubber must part into a section that will pull off from outside the curve of the jaw and a section that will pull off INSIDE the curve of the jaw.

Y'know that old trick of putting an orange peel in your mouth and smiling so you teeth look like orange peel?

You essentially want to place an aluminum 'SHIM' in the space between the upper and lower teeth. It must fit tightly into every nook and cranny so that when you paint or pour rubber over the item the rubber on one side of the shim can not come incontact with the rubber on the other side of the shim.

This would most likely require making a mold in at least two pieces.

Again- I recomend you check out the FAQs page or do a search of this site for threads mentioning molds and read up on the process as much as possible,

I would recomend using bodydouble fast set silicone, you can purchase this at www.smooth-on.com its found under life casting. Also purchase the thinner that goes with it.

Use the thiner with the two part bodydouble and brush on one or two thin coats to eliminate any air bubles, then build up with out the thinner. this product is awesome because its ridged and flexible and hardens in a few minutes instead of 4 hours or more like latex molds. For dealing with large under cuts, cut up some sponges and seal in place with silicone while silicone is still setting, the sponge will hold the shape and alow movement when removing the piece. Coat entire piec with the silicone and build up extra where you want your cut line to go. Make a plaster support shell in two to three pieces by taking some modeling clay and marking off an area and filling with plaster, then remove clay and coat edges with vasilene so the plaster pieces do not stick together. Once that is finished take an exacto knife and carefully cut along the cut line you made, peel off of sculpture, then then use silicone to seal the mold back up, cut a small hole where you want to pour in your material, pour some in and rotate mold to eliminate air pockets, and continue until filled, use plaster supports hold together with rubber bands and thats pretty much it. Once piece has set, cut out with exacto knife. I was able to make this reproduction with out use of plaster support, the silicone was sturdy enough to hold the shape.