A tool out there to sputter silver and gold for Scanning Eletron microscopes can coat the glass with the layers of silver and then a thin layer of gold to protect the silver from corrosion. Edax Scans on SP 3420's reflector on the tender showed that the tint was caused by gold diffusion into the silver. Gold is a very stable material as far as corrosion goes and was used to protect the silver.

Robby