"The Natural Philosopher" wrote in message
...
I've always wondered how effective it is to glue a glass slide over a
crack. It depends rather critically on the bond between the glue and the
glass being stronger than the glass itself - otherwise as the wall moves,
it breaks the glue/glass bond (or the glue/wall bond) and the slide
remains intact.

Even that is as helpful

Assuming you can *see* that the glue joint has failed. Not as easy to spot
at a glance as a crack across the glass.