Pretty soon he was using silicone rubber to make two-piece, high-quality molds of lenses, good enough to try a few casting shots with epoxy resin. [Zach] ran into a few problems along the way ...

Resin casting lets you produce parts that would ... you’ll cast the mating silicone mold on top. There are two methods I employed. My usual is to use light glues like rubber cement, or blue ...