Ireane;         this is Jim Hicks speaking (first appricticeship in S.G. May
'61)

I have to respectively disagree with some of the comments on the rippled
glass. Leaded glass is well suited to withstand weather given some basic
perameters. 1st - are the panels designed to withstand their own weight ie.
linier design and re-bars 2nd - glass and lead withstand the elements very
well - lead, although very reactive with oxigen, its oxide is extremly water
proof so after the initial reaction there is little detieration- also the
formula for the lead needs to be such that there are trace amounts of other
elements ie. antimony that make the lead stronger - rain and the other
elements don't effect glass very much if the glass making process was sound
itself. There is a fair amount of de-laminating of glass not made with the
correct amounts of soda-ash or painted and not fired correctly.
I think that the use of protective glazing is mostly not from the elements but
from vandals.
Other problems with pro. is heat build up and condensation. The latest
solution has been to have the pro as the outer layer (completly sealed) and
the stained glass layer to be suspended on the inside so that air circulates
freely. On problem with this though, I heard at one seminar was that sealing
one building that way had changed the buildings inner weather and had held in
all the moisture and contaminants and a solution had then to be invented for
the new problem.
I think Spencers comment ! is a bit strong. To have pro or not strickly
depends  on local conditions and outcome decisions. For instatnce, how much
light do the windows get and when?
If I were you I'd call Vic Rothman @ 212-255-2551 for more. He does more S.G.
than I do nowa days.
jim