Homemade cold cast bronze ornaments

Spotted in the MAKE Flickr pool:

Matt Jones made these Ojai Post Office Christmas Ornaments for his friends who just moved there. He drew the design in a vector drawing program, used a laser cutter to cut out pieces in acrylic and cardstock, then made a silicone mold of the model for casting. I always wonder how people make the models that they use for molding, so I appreciated his in-depth explanation. The full photo set is here.