This is the second part of a two-part series on making a silicone model from a human body part. The first part of the series was Replicating body parts in plaster.
Step 1: Go get the stuff you need
- 1 pint of Dragon Skin Platinum Silicone Rubber
- 2 pints of PMC-744 Urethane Rubber (although, considering this triggered an extreme allergic reaction in both my assistant and I, I'd recommend using Rebound 25 silicon rubber, if possible)
- Smooth-On Universal Mold Release
- Ease Release 800
- Shellac or lacquer sealant
- 2 two-pint measuring bowls
- 2 cheap paint brushes
- 2 wooden mixing sticks
- a plaster cast of a breast
- a white painter's body suit
- a pair of thick rubber gloves
- a pair of nitrile gloves (non-latex)
- a couple of thick garbage bags to dispose of chemicals
- an empty 2 gallon water container
- a razor blade
- a hot glue gun
- duct tape
***a well-ventilated area or a nice, windy spot outdoors***
Step 2: Seal the plaster
Once the sealant is dry, spray the inside of the rig with Universal Mold Release agent. Gently spread the release agent around with a paintbrush and then let dry for thirty minutes.
Step 3: Build a frame
When you've found a suitable container or casing for your model, cut a hole in the bottom into which the plaster breast fits snuggly and then glue it in place from the outside with hot glue. (To ensure that the surface area of my mold would not be much larger than the surface area of the plaster breast, I added an extra wall to the inside of the container. While not necessary, I'd recommend it, though, frankly, it depends on the size of the model.)
Make very certain that the glue fills in all possible cracks from which the polyurethane rubber may leak. (To be on the safe side, you also may want to tape around the outside of the rig with duct tape.)
Step 4: Mix the pourable rubber
What I did was to pour part B and thoroughly mix it in the container. Then I poured in part A and thoroughly mixed the both of them together. I continued mixing for a couple of minutes, but not for too long since the pot-life on PMC-744 is only 15 minutes.
Step 5: Pour the rubber mold
Place the mold somewhere outside where it is dry and not windy (or in a well-ventilated area) and let it sit for about 24 hours.
Step 6: Remove the mold
Trim away any extra rubber from the mold-making process.
Step 7: Bake the mold (optional)
Be sure not to use a toaster oven that you ever intend to use for cooking ever again. Do this outside or in a very well-ventilated area.
Step 8: Seal the mold
Step 9: Mix the silicone
You probably won't need to use all of it, unless the breast you are working with is very large. Guesstimate about how much volume the breast will take up and then increase that number slightly.
Once you have an idea of the volume you are working with, divide that number in half to determine how much of part A and part B you will need. In other words, figure out the volume of the whole and parts A and B will be half of that amount.
Pour out part A and mix thoroughly.
Next, before pouring mix part B thoroughly. Once mixed, pour an equal amount of part B in with part A.
Mix parts A and B thoroughly for at least 3-5 minutes.
Step 10: Pour the silicone breast
Give your mold a few good hits with something solid (like a paintbrush or screwdriver) to force air bubbles upwards and prevent them from ruining the surface.
Let it sit in a well-ventilated spot for 24 hours to fully harden.
Step 11: Demold the silicone breast
Remove your silicone breast from the mold.