Tuesday tips - Plaster molds

Probably, for me anyway, the least glamarous part of making molds is casting my model in plaster. Last week I brought you through the process I use to make clay models of a design.  While not so glamorous, casting your model in plaster is the most critical part of getting your design into production.

First up is selecting something to contain the plaster. I'm pretty simple with this.

For my dragon fly pendant, I used a ricotta cheese container. Loved the ricotta in a yummy lasagne. Loved the cost free upcycled mold form.

Problem with this mold form is that the bottom is not flat. I solve this by placing a slab of clay into the bottom of the plastic container.

Then I attach my clay model to the slab in the bottom of the mold form. What I do is make a bunch of cross cuts into the slab with a needle tool and the back of the model. Then I brush on water to make a bit of a slip on the surface of the clay slab at the bottom of my mold form. I place the model and gently tap it to get it to stick to the slab of clay. I find this useful as it keeps the model from 'floating' when I pour the plaster.

Sorry, but pouring plaster is a pretty quick process and I've only so many hands to take photos. But in a nutshell, I pour from one side of the mold form an let the plaster flow over my carved model. I do this to avoid bubbles forming on the model. Not a nice thing to have happen as it will transfer a 'bump' when you press your pendant. See those bubbles on the top. I gently tap my finger against the mold for to get little tiny bubbles in the plaster to rise to the top where they won't interfere with my design.

Above is the finished plaster mold and a pendant I pressed from the mold. I go back in with a file and scrape back the edges of the mold around the pattern so that I can release the porcelain pendant I pressed without it dragging on the edges.

Lots's of things you can use for mold forms. Including clay scraps. Below is a pic of a clay mold form I've used in the past.

Truly, I think there are as many ways to make plaster molds as there are people working in clay. This is just a couple of examples that have worked for me.

What do you do? Got any questions? Comment and I'll get back to you!

Next week I'll go into a bit of technical plaster stuff. Not really eye candy but if you are casting models this may save you a bit of time.

Thanks so much for stopping by!