Preserving exposed platters from corrosion and fingerprints

About ten years ago, my brother (also a tech) and I would take our Saturdays to shoot the hell out of the dead hard drives we'd collected during the week. I've written about this before. A bullet to a dead Seagate is really poetic justice... At any rate, Mike decided suddenly to make money on these dead drives instead of shooting them. Not nearly as much fun though... He would drive out the spindle, secure the platters, and insert a clock mech where the spindle used to be. The outer disk platter made the clock's 'face'. The look very cool. He called his 'hard time'. I told him he ought to sell them by the megabyte... The platters are very sensitive to fingerprints and other environmental contact. What is a good, quick, and cheap way to treat the platters before completing the clock that will seal and protect the platters without yellowing or cracking? Regards, jeff