From my experience of metal casting, I also produce selected objects in cast plastic. I add bronze powder as well as tints to the plastic when it is in the liquid form which creates depth and added texture to the final product.
I create rubber molds from patterns that are either modeled or modified from another object. The cat lightswitch cover was modeled; however, the bark and stick lightswitch covers were started by using the actual materials.
The mini car series are a nod to my favorite childhood toy. I have modified a variety of ten cars into drawer pulls and magnets as well.