Bill, I'm not an expert on the coating issue. I usually don't coat my coils, but many others find that it is helpful for preventing arc breakdowns, etc. The coating is nice for holding the wire in place too, esp for enameled magnet wire, and a thick coating gives a nice smooth look to the coil. Shellac, polyurethane, epoxy, etc, should all be fine. If you plan on transporting the coil, a coating will protect the windings too. John Freau