Casting Process: Molding

I like recording my process and techniques, mostly because I want to remember how to do this when I'm old and I've forgotten, and partly because it can get pretty complicated, and my instruction was lack luster. Hopefully I can help other people figure this out. I ruined plenty of molds before I ever got one to work properly. Here I'm making a one part plaster waste mold- So, once the piece is cast in fiberglass, the mold is broken off of it and destroyed. It's a one shot chance... hopefully this one will work out... fingers crossed!

Once the modeling was finished on this piece, it's time to start molding and casting. I built a foamcore wall around my model 1" taller than the clay's highest point. I filled in all gaps with hot glue, keeping the inside as smooth as possible. Once built, I covered every surface inside the mold with a thin coat of vaseline- this acts as a release agent, so the plaster doesn't stick to the surfaces. Never leave brush marks. That extra little chunk of wood at the neck is there to create a positive shape in fiberglass once it's cast- I'll be able to drill holes into it and attach the separate wooden head there.

Once everything is covered in release agent, it's time to add plaster. The first layer of plaster is called a splatter coat, and it's supposed to be really thin and runny. You throw the plaster on the piece like Pollock till it's covered, then you blow really hard on the details to eliminate trapped air pockets. Let it set (plaster heats up as it solidifies; let this layer cure to cool), and continue adding thicker layers till it reaches the top of your mold wall. Then, let it sit overnight and then remove the wall and dig out the clay. I'll be doing that tomorrow night... I'll take more pictures.


Here's some glass I blew this weekend, Tim McFadden gaffing:

Manta Horn Platter

Saturn in the annealer