Prop Builder’s Molding & Casting Handbook
Basic mold-making skills
Meant for prop builders in theater or film, this how-to book is the best overall guide for making molds and castings for any reason. Casting is a handy skill for any craftsperson — dollmaker, restorationist, Halloween fan, furniture maker, or handyman. This guide treats the many different modern substances you can use (about 30), educating you on what’s good for what, and taking you through the particulars for each kind of casting process. The guide assumes an ease with general shop skills and a willingness to deal with messy chemicals (and clean up!). Once you are comfortable with making molds and casts, you’ll find all kinds of creative problems can be solved with it. (Watch an episode of Mythbusters.)
The mold-making materials include plaster, two kinds of alginate, two forms of silicone rubber, latex, and hot-melt rubber.
Moulage is a better molding material than plaster for this job because it is flexible. A hard plaster mold would most likely break -- either when you attempted to remove the original pattern, or when you tried to release the copies (also made from a hard material).
We added Plasticine, sculpting the pattern to make it look a little more like an oil lamp and a little less like a teapot. The addition of the pedestal to the finished casting will also help to convey this illusion.
Hot-melt glue (ethylene vinyl acetate or EVA) is a thermoplastic with qualities much like those of other hot melts: it becomes fluid when heated, and is ruggedly solid when it cools to room temperature. In fact, it has enough of the "right" characteristics to make it a useful casting material. We will demonstrate casting with hot glue as we construct a crown from scratch.
The filigree headband of this crown was made of a standard lamp part, called "brass banding." The finials are twenty repeated castings of EVA (hot-melt glue).
When you can use an authentic item as a vacuum forming mold, the thin plastic casting will be very realistic. This mold is a pattern of real roofing tiles, caulked with plaster.