Grunff wrote:

Tony Williams wrote:
................ I'm fairly certain I saw drain slots, along
the base of the sandwich, opening up to the airgap between the
glass sheets.

That would be a most unusual arrangement - apart from anything
else, they'd be permanently misted up! Are you sure the sealed
unit had slots at the bottom?

That's what I thought I saw. Some early secondary glazing also
had holes along the bottom of the 'sandwich', specifically to
avoid misting up.

I must have a closer look. Perhaps the slots at the base of
the sandwich were leading to a trough that holds some sort
of moisture absorbant.

--
Tony Williams.