I am looking to create a object out of something soft enough I can use an exacto knife to carve my desired shape, and use that to create a mold. I am worried about them bonding together. Is Styrofoam the right thing to carve? The only other thing I could think of was soap.
Some other considerations for your mold master could be modeling clay, soft woods such as Balsa, Plastics or a combination of materials. To help prevent bonding/sticking is to use a mold release......simply spray mold release on your master prior to pouring your mold making material. The petroleum products used in aerosol (the mold release) could have an adverse effect on Styrofoam....if using Styrofoam ,test on a piece first before getting too deep in your project.