Originally Posted by jab

That's epoxy, just some quick-drying stuff that comes in a double-syringe pack from a hardware store. To apply it, I first placed some electrical tape around the edge of the circuit board, perpendicular to the edge, to act as a form. (You know, like when pouring concrete.) Then, I just mixed some of the epoxy and poured it in until the connections were covered and things looked good and sealed.