The silicone that I'll be using for this mold as I stated earlier is GI-1000. Most silicones come in 2 parts- the base silicone, and a catalyst (to harden the silicone). Weigh out your silicone (I use a digital scale- there pretty cheap) and mix in your catalyst 1:10 mix ratio (for GI-1000- 1 part catalyst for every 10 parts silicone base). Once your silicone is thoroughly mixed it is advisable to de-air your silicone in an evacuation chamber to remove all the air from the silicone. However, If you (like myself) do not have an evacuation chamber (there not very cheap) use the high pour method. The high pour method is when you stand high above your sculpture and slowly pour a very thin stream over your sculpt. As you are pouring using the high pour method most of the air bubbles get stretched out of the silicone. Just so you know de-aired silicone will always be stronger but the high pour method gets the job done.
When pouring silicone over a sculpture it's very easy to get trapped air bubbles against the sculptures surface (usually in undercuts and small indented areas). To avoid this I cover my entire sculpture with a thin layer of silicone, and use an air compressor (or canned air, pictured to the right) to blow the silicone into all the detail and break those air bubbles apart. Be careful to not blow too hard on your sculpt; you don't want to accidentally separate the clay seam line from your sculpture. Another option would be to apply a thin layer of silicone to your sculpt and clay surface with a brush. Once you are sure that you got the silicone into all your sculptures detail (this includes all the key holes for the mold), continue to finish your pour using the high pour method.
Here on the left is our finished side one. Now we get to sit and wait for our silicone to set up, usually 16-18 hours. You will know when your silicone is fully set when you can push on it without leaving any indentation in it. I usually just wait to the next day before starting on side 2. In case you didn't earlier, remember to cover up that clay with saran wrap. Now go get a burger, or better yet start up another sculpture while your silicone sets.
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Working The Silicone Into All Your Detail: 
