The glass is not shattered, it
just has a crack across one corner, and that section has settled into
the frame, so the crack is open about 1/16".


My question is what to use to glue it. It should be clear, so that
leaves out JB Weld, which I am sure would work, since it seems to glue
anything. The other options I can see are superglue, which is
something I have never seen to work on much of anything, or clear
silicone caulk, which seems the most likely thing to work.

Before doing anything, I thought I'd see if anyone has any other ideas
or suggestions.

Like I said, this is thick glass, and the crack is clean. I just need
to remove the wooden strip and lift the piece a little to glue it,
then stuff putty around it before replacing the strip.

Silicone is indeed the best choice. I would use a flexible filler, since the
point is to seal the tiny crack, not mend the glass. Clear silicone
adhesive, squirted in with a fairly small-diameter nozzle cut. Then
immediately smoothe both sides at once (to keep glue from alternately
squeezing out one side, then other) with a safety razor edge or putty knives
held at low angle to glass. This will compress the glue and slightly
overfill the crack. Let dry completely overnight, then razor blade off the
excess, running the blade in direction of the crack orientation.. Any
hardening glue is pointless, as you are pulling the glass in the Spring,
anyway. Epoxy and super glues generally work best when pieces are in direct
contact, and work poorly as fillers. Epoxy also runs, unlike a gel like
silicone.