NOTE: You can make the sprue and air hole out of clay if you would prefer, they just won't be quite as uniform. I will explain what these are and why they are necessary as we make the mold.
These will act as your sprue and air hole. Two very small additional things you'll need are short dowels:two pieces 5/8" long, one 1/2" in diameter and the other 3/16" diameter. *(x2) 2.8 lbs kits for this particular mold. Mold release - I use Mann Ease Release 200.Stir sticks (paint style and tongue depressors).Casting material (I used casting plaster).Mold making material (I used Smooth-On Oomoo 25 Silicone Rubber*).Kraft paper, newsprint, or cardboard (to cover & protect your work surface).Mold wall materials (I used pre-cut acrylic/plexiglass pieces).Here's a list of what you need to make a two part mold: Finding the halfway line (aka part line) of the handle and mug body and casting one half of the mug first and then the other, allows you to easily remove the mug from the mold. A mug without a handle (if it has a good draft angle) can be a one part mold, but add a handle and you are introducing a protrusion (the handle itself) with a through-hole, both of which would get stuck in a rigid one part mold.
#Casting plaster in silicone mold free#
Are completely in the round, with no flat bottom (like a sphere)Īnother reason to use a two part mold is if you want to make a rigid mold of a model with undercuts (i.e.: a plaster mold for ceramic slip casting.) Because there is no give at all in the material, you must find the part line of the shape that will allow the two mold pieces to pull apart and the model or cast to be released, free of undercuts.Ī mug with a handle is a good example of this.Are thin and top heavy and can't stand up on end (like a mallet).
Are thin and floppy and can't stand up on end (like a fish).Have holes going all the way through them (i.e.: a donut!).Dome examples of models that require two part molds are those that:
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