Great questions and replies. I haven't done this with vellum, but what about sealing ( encapsulating ) the package. The name of the product used slips my mind, but Hugh Phibbs taught the procedure in his classes. It's a heat activated foil that you wrap the item with and then adhere to the glass, to seal the package. You can also make something similar with heavy aluminum foil and a heat activated fabric adhesive, (if I recall it corectly) it to was taught in the class. The only concern is if it were to leak, like a watch seal gone bad, it would then be exposed to the elements, making them harder to release themselves, like condensation in the watch. If I were still in the business I would do this as a long term test product. Vellum has always been extremely sensitive to enviormental fluctuations.