Step 1: The Materials
1. plaster of paris for the mold of the shoes
2. cake pan for the mold container
3. Ease Release 200 mold release agent
4. PMC-790 urethane rubber
5. plastic mixing cup
6. stir stick
7. kitchen scale
Step 2: The Mold
The mold making process is pretty straight forward:
1. mix up the plaster to about peanut butter consistency
2. press the shoes into the plaster to capture the shape of the bottom of the shoe (keep the shoes level front-to-back and side-to-side or you'll have a funny walking feeling on uneven shoes)
3. add traction or designs to the bottom of the new shoes by drawing lines, shapes, or words into the plaster
4. let it dry thoroughly
5. spray the release agent on the mold as recommended by the instructions on the can
(the picture is actually of the shoes being cured to the rubber, but you get the idea)
Step 3: The Urethane Rubber
Mixing for PMC-790:
1. place the mixing cup on the scale and press tare (if your scale doesn't have tare just write the weight down so we can subtract it later)
2. weight out an appropriate amount of part A into the mixing cup and write down the amount (if your scale doesn't have the tare function then you need to subtract the weight of the cup from the current weight to get the weight of part A)
3. press tare and add part B until the scale reads 1/2 the weight of part A (if your scale doesn't have tare, just add 1/2 the weight of part A to the current weight and that's you're target weight)
4. follow the mixing instructions on the bottle to make sure you get the two parts mixed well
When you've got the rubber mixed, pour it into the mold all the way to the top. Then lightly press the shoes on top. Again, make sure the shoes are level front-to-back and left-to-right.
Step 4: Trimming the Rubber
For this step, just pull the shoes out of the mold. You can break the plaster if you need to, just get the shoes out. Then use a sharp knife to cut away any excess rubber around the edges and let the shoes cure for the rest of the time recommended on the bottle of rubber.
You can see how much plaster came out of the mold with these shoes. A sealant would have prevented this, but the shoes are still usable with the plaster on there. Eventually the plaster will flake away.
Step 5: Some Take-aways
2. There are lots of silicone mold materials that are actually easier to work with than plaster of paris. They mix just like this urethane rubber does and don't flake away like the plaster.