ameijers wrote:

If the fogging is a problem in the barn for you, pull the
glass sandwich from the frames. Cut the panes apart with a
razor knife and scrape off all the old sealant. Some
desiccants, silica gel, can be regenerated by either nuking
them in a microwave oven or oven placed on self clean.
Others need a vacuum to be dried out. In either event, dump
the old desiccant and try to regenerate it. If you can't,
then go to a hobby store and buy a pound or two of new
silica gel. It's used for drying flowers, for instance.

Refill the channels separating the glass sheets after you
very thoroughly clean the glass. Silicone sealer will work
for several years, but my own little "trick" is to cut
aluminum foil to 2" wide and place it over the silicone
sealer while it's still uncured. That is a REAL vapor
barrier, IMHO. Pros use a 2-part polysulfide, but unless
you can get a glass company to sell you some, along with a
gun, you're out of luck there.

An alternative is to take the panes to a glass supply house
and get a quote for cleaning and resealing by a pro.

Nonnymus