Weird stuff between window panes?

[Growyourown]

Hey guys! We are newbies doing our first restoration on a 1972 Overlander 27'.
The two upper windows (are the called stack windows?? I think those are the lowers? I dont know.) have some weird flaky material in between the window panes, and we're not sure what it is nor how to get it out.
I've attached some pics - any ideas?

[idroba]

Airstream double pane windows were a double pain in all ways. When they leak (and all double pane windows, even home ones leak eventually) and the silica gel used to absorb small amounts of moisture becomes saturated, it causes problems like you are seeing. I am sure there are some threads on the subject, but it is not going to be easy or inexpensive to fix. A good idea that just did not work out well over time.

[overlander63]

It may be easier than you think. If you want to permanently remove the inner panes, and they are plastic instead of glass, simply heavily scribe a line across the inner window in a big "X". Punch the plastic in the moddle where the "X" crosses. The inner pane will break in 4 pieces. Remove the 4 pieces and clean the gunk out.
It's not a perfect world, so you may have to remove part of the inner trim to get at the edges of the inner pane, and either pull, pry, or scrape it off the frame.