I used clear epoxy resin, jeweler's grade on butterfly wings (obtained from a butterfly farm after their natural death) and it turned the wings dark. It did, however work nicely on a lightly colored transparent wing. I'm not sure how to correct this or if there is an alternative that is just as easy as epoxy resin.
My plan was to make Christmas presents out of them, but the clock is ticking. Not sure if I'll get it figured out in time. I would like to stick with epoxy resin if there is some simple tweaking, but any suggestions or alternative methods would be much appreciated!