Microwave door discoloring??

[BLACKJACK]

We have an over the range microwave, the door is a glass, see thru type, inbetween the layers of glass and whatever else its made of, its starting to discolor, turning brown. You can't get to that stain, its between the layers. What causes that??? Every morning I nuke a cup of water with a tea bag in it, that tea bag has that little metal staple holding the tab on, my wife thinks that could be the problem.

The microwave works fine, but now that we might end up getting a new frig my wife is pushing for a new microwave too, thought I'd ask to see if anyone else has this problem with their microwave, and what causes it??

[The_Duckslayer]

It's called aging! My mom's is doing the same thing and there is no one that cleans better than she does! I think that the seal on the glass may not be totally sealed and that some smoke from cooking may be getting in there. The white of the door is starting to yellow as well. The little staple in the tea back is not causing it and will not hurt the unit at all. Take care and N Joy the Hunt././Jimbo