If you want a really permanent mold, Here is a good system. You end up with an exact copy of what you carve plus the thickness of your plastic.
The concept is to make a master, make a mold from that, and hard copies of the form from that mold. You can make multiple copies from the mold.
So, carve a foam form to exact dimensions. Fill the foam surface with spackling compound. Sand smooth.
This is your master, not the final item. Add a filler piece about 1/4" under your master and match it to the master. It can have a very slight outward slope. 3 or 4 coats of clear epoxy thinned with alcohol to seal the surface and sand to perfection. Primer and filler any imperfections. Glue this form to a plate of plywood and build a wall all around it. NOW, give everything 3 coats of wax. I find liquid Turtle Wax is quite good enough. Wipe on a coat of PVA, then when dry, spray on another coat.
Make a box around the form and fill it with plaster. When set and dry, it should pop right off. You probably will have to destroy the walls of the box, but they will never be needed again, anyway.
Seal the plaster female with dope or epoxy and polish it to perfection. Again with the wax and PVA. Now you can fill the female mold with plaster and make all the canopy forms you want!
Since no heat or stress is involved with the original form, you can use vinyl tape for canopy lines and details.
I got to tour Peck Polymers once, and their final forms were metal filled epoxy. Of course they needed hundreds of copies.
I have also used this technique to copy existing canopies. Fill the canopy interior with plaster after applying the release agent, add the spacer underneath and proceed as above, or just use the plaster copy if you only need one or two copies.
Topic: Carving a canopy plug (Read 1347 times)