*** WARNING: Because of the body part chosen for casting (in this case, a woman's breast), this Instructable may contain material considered offensive or objectionable to some readers. Viewer discretion is advised. ***
Step 1: Gather your materials
1) Dermagel - at least 2 pounds (or equivalent dental alginate)
2) Plaster - at least 2 pounds
3) Plastic container for placing body part inside of
4) 2 plastic mixing bowls - preferably with measuring lines (might get ruined)
5) Plastic cups for pouring materials
6) Duct tape
7) Metal whisk
8) Wooden mixing stick
9) Gram scale
10) Box cutter
11) Flathead screwdriver
12) An old towel
13) An assistant (optional, but highly recommended)
Step 2: Select a body part
The first thing you'll want to do is decide what to replicate. Some things are clearly more challenging than others. For instance, casting a finger is definitely easier than casting one's right breast.
However, I say go with whatever will make you or your robot happy.
Step 3: Prepare your container for casting
If you're casting something that you are capable of sticking into a bucket (i.e. a hand, foot or elbow), then all you need to do is find a container slightly bigger than the part you are trying to cast.
If you're casting something like a boob or a belly button, then you have to find a container that will fit nicely over the entire area of the body part.
For my first cast, I tried using an old yogurt container that was cut in half (below). This container cut off part of the breast. So I tried again by cutting in half a two-gallon water container and that was more than large enough to cast the body part (not shown).