See Notes about the instructions.
This method probably can be done with other plastics manufactured for the same purpose, but I'm using E-Z Water as that is what the hobby shop had to offer. The plastic is in the form of small pellets as you can see in the picture. These can be melted in a pot on a regular stove and used for casting although they are normally used in creating lakes and streams for dioramas and miniature railways.
There are some important things to note when using this stuff:
1) The pot cannot be used for anything else after this (I bought a cheap stainless steel bowl for this purpose).
2) When the pellets start to melt, keep an eye on the pot to make sure the plastic is not getting too hot.
3) When handling the melted plastic, remember that it is *very* hot, so don't get yourself burned.
4) If you happen to knock the pot over, you can be almost certain that whatever it was that the melted plastic spilled on, it is ruined (if it is a glossy, non-porous surface, you may be able to remove the plastic entirely once it has cooled).
For the mould, you need material that can take the heat. If you want transparent plastic, it also needs to have a glossy surface. I used very thin metal sheet. Bend it to the desired shape and use adhesive tape to secure and seal the mould. If the mould is a heel, like in the picture, you need something to keep it in a vertical position. I used oasis flower foam.
Pour the melted plastic into the mould. Wait for it to cool. Then remove the casting from the mould. You will probably need to remove the tape and open the mould to get the casting out. The picture on the right shows a finished shoe heel. There should be as little air bubbles as possible, so this one is not a very successful end product.
The following pictures show an example of a mould for making the entire sole. You need to trace the shape of the foot on the metal sheet, cut it out, and use adhesive tape to attach a strip of the sheet to the cutout, following its contours.
The only problem with this technique is that making high heel soles is virtually impossible. Wedge soles may be possible, if you make the mould so that it is upside down.
The next pictures show what happens when the plastic gets too hot. It starts to burn and its color changes. If you compare the color to the picture of the heel, you can see that these are more amber. It is a nice color, but if the plastic had gotten a little hotter, there might have been trouble. And I noticed that if you heat the plastic just enough to melt it, it will not melt the adhesive tape in the mould, but if you get it so hot that its color changes, it will melt any adhesive tape it touches.
As you can see, you can place small objects inside the mould before pouring in the plastic. I tried also pouring in a little plastic, inserting some items and then pouring in the rest of the plastic, but this leaves a visible line in the plastic.
It is possible to use silicone rubber moulds for these castings as well, but that will produce matte surface as can be seen in these Tiny Kitty wedge soles.
So I just had to see if it is possible to make wedge soles. It was not very easy, but it is possible. Below are pictures of the moulds and the result. These are Tiny Kitty size. The red inside the plastic is glass beads.