Mold Release:
There are many things that you can do to insure that your silicone molds will last. One of the most important things is to use a mold release. Silicone molds (in most cases) do not need a mold release, but using one will help you in the long run. I'm casting my molds for this tutorial in Silwhite (a SILPAC, INC. product, a two part plastic). In many cases if you have ever bought a model kit, it was cast in Silwhite. I will use baby powder as a mold release for this mold. This is the mold release that you should use for any hard casting material (in a silicone mold). Using baby powder as a mold release serves a couple of functions. First of all, air bubbles will not stick to the surface of your mold because they have nothing to grab onto; the baby powder helps to prevent this. Secondly it will help you with the de-molding of your mold. Pour some baby powder onto your mold's surface and use a brush to work it into all of the detail. Then use an air compressor (or canned air) to blow the whole surface off (mouse over the left picture). You can see that a light baby powder residue will remain, however this will not interrupt all the detail of your sculpt being represented by your casting, because the powder will absorb your material. I'd like to point out that this step is not necessary if you are just looking for a couple of castings, but if you do use a mold release it will significantly increase the amount of copy's that you can get from your mold (especially if your sculpt has a lot of intricate detail).

Silwhite Pour:
Silwhite is my favorite casting plastic, and if you are looking for a material to cast your sculptures in I highly recommend that you at least try it (it's a hard, paintable plastic). When you are casting in a silicone mold, use the least amount of pressure as necessary to keep your mold closed. On the picture to the right you can see that I made plexiglass shells for my mold so that I would have steady, even pressure. I held the two pieces of the mold together with rubber bands. If rubber bands are not strong enough for you, use mold straps. I would advise against using clamps for your silicone molds unless you built a hard stone jacket for your mold. Clamps can and usually will compress your silicone to an extant that your casting will be warped or your seam line will be misaligned.

De-molding Your Casting:
Take care when de-molding your castings, don't rip your mold open and expect it to last for very long (Treat it like a lady). First go around your entire mold and part the seam line, and then carefully and slowly pull the two pieces apart. Never force it open, if you feel resistance- try opening it another way. Silicone can rip if you are not careful with it. You should always save your first successful casting as your master. Keep your master in a safe place in case you ever need to re-mold your sculpture. Some people save their original sculpture as their master but personally I'd rather keep a hard plastic copy rather than a fragile Super Sculpey and Primo copy as my master.