Step 1: Prepare and clean the prototype. You must make sure your original molds perfect, fix the original mold on a board, then using some assistant material (like cardboard) to make a frame for to surround the prototype. The frame is no need, if we make the mold by brushing way. Step 2: Take the silicone and catalyst as the ratio 1:1 (silicone:catalyst= 1:1), mix the silicone rubber and catalyst evenly. Notes: rtv silicone rubber is a kind of flowing liquid and it contains two parts. Part A is a kind of flowing liquid and part B is the curing agent. Remember to mix part A and part B evenly, otherwise the silicone rubber will be partly solidified and this will bring troubles for your final operation. What's more, the finishes molds will have a short life. All of these will cause a waste of silicone rubber. Step 3: Vacuum pumping. After mixed the silicone evenly, it is better to release the bubble by vacuum pumping. Step 4: Pouring cast or brushing cast. After released the bubble, we can pour/brush the silicone rubber on the prototype. Notes: Please finishes all the steps within the operation time. If not, it will cause cross linking reaction, and no more further steps will be available. So, we have to pay attention to the pot life and curing time.