Making a slip casting mold - first steps

[Jeff Longtin]

In the early years of my mold making life I read countless descriptions of molding projects starting with embedding a model in a bed of clay. I tried this a few times but found it really annoying. Instead I decided to use foam core to create the parting line/seam. This method makes the process really easy.

The first picture shows a bottle shape drawn on a piece of foam core. (Over a drawing for a previous project.) I cut this shape out. This piece of foam core helps me set the parting line for the mold. 

The second picture shows the mold side after the first pouring. You can see where the plaster fell between the foam core and the bottle form. This is easy to clean. When I pour plaster, for this step, I let the plaster thicken to the point where its like pudding. That minimizes the amount of plaster that falls between  the form and the template.

Also, in this photo, you can see clay where a sprew should be. I was undecided on how big the sprew should be, so I filled the space with oil clay, so I can drop in a sprew when I'm ready to pour a final casting. 

The third photo shows the plaster mold part after I cleaned up the edges but before I drill the key holes.  The nice thing about starting the process with a plaster template is that I can take my time and plan the size of the mold and location the key holes. I can also see if the parting line is good, or if I need to make an adjustment, before I pour the first mold part.

I hope this helps anyone making their first mold.

[Min]

Clever way to do this, thanks for sharing.