Flyboy, what do you mean by offgas?
Interesting seeing the brass coated in shellac. I've used it over copper inlay before. The copper darkened but so far hasn't turned green. I've also used it over abalone inlay, giving it a slightly darker colouring. I've used both the orange flakes and a hard blonde premix. We even went to an aviation supplier to buy the purest alcohol. Shop-bought is 95% only which I'm sure is adequate, but if you can find 100% that is ideal. Shellac and water really don't go well together.
Mainly I've used shellac on musical instruments - fiddle, dulcimers, hurdy gurdy- walking sticks, and a dogfood box.
Shellac has so many uses but I don't think on the outside of beehives it will be useful at all.