pour spout or pouring duct

The pour spout is an opening into the mold through which liquid material is poured. Normally, it’s placed at the highest point of a mold when you’re pouring, which could be the bottom of the mold. When pouring, the casting material has to fill the mold completely. Often, the bottom of a sculpture works as the pouring duct or spout and you won’t have to make another. The spout has to be on the parting line and in a place that doesn’t interfere with your design.

types of plaster

United States Gypsum sells several types of plaster. 30 and 45 minute casting plaster which are both great for mold making and working a sculpture directly in plaster. Fiber Glass Reinforced (FGR) plaster is for making 1/8″ mold shells/mother molds using fiberglass blanket. Hydra-Cal is a great casting plaster. It can be worked after it’s cast. Hydra Stone is also a great casting plaster but harder and hard to work after it’s cast. These last two can be referred to as “cast stone”.

making a plaster molding 1

beginning of the wax original

finishing the first original segment

one piece dump mold

I was hired to make a chandelier molding following an already existing logo. The first thing I did is buy a round board and use paper to draw out the logo into equal parts. I cut out one piece of the paper and started one segment of the sculpture in wax. After I finished the first segment exactly as I wanted it, I made a one piece dump mold: a 1/2″ layer of clay and a dump spout, covered it with a shell or mother mold using FGR with a fiberglass blanket to make a 1/4″ shell. I cast wax into that mold until I got all my segments. I think it took 8 casts to make the entire circle.

making a plaster molding 2

adjusting the segments

placing the segments

wax original-ready for mold making

At the time, I liked working in wax, but this original could have been made in clay or plasticine. It would have had to be made as one unit, instead of with several segments.

I did a lot of fixing and repairing before making the final mold.  There are several types of soft wax that you can buy to repair small holes and fill cracks.

making a plaster molding 3

Making the clay blanket over original with plastic between wax and clay to protect the wax original

the center piece is to keep a hollow for chandelier wiring

Clay blanket and half of the mother mold, notice metal shims to divide shell and notice the raised clay for registration. It has two dump spouts, seen here in clay.

I painted on a thin coat of polyurethane just before registering the mother mold for the dump

I don’t have the piece de resistance, i. e. the finished mold! Sorry. It looks identical to the mold of one segment, only it’s round.