Iguana Gazing Ball

This is the second Gazing ball that I have made.  I have learned a lot.  This one
developed a crack after sanding and painting the images the bowling ball.  I
could have stopped at this point, but I did not.  I decided to fill the crack with
silicon glue. I painted over it.  The crack was gone.  I glued all the glass pieces
on the ball, and then grouted it.  Unfortunately the crack developed again.
Fortunately, the grout and glass are still securely in place, even after two coats
of grout sealer.  The only evidence of a crack is a fine black line that curves
with the curve of the ball.  The question "why bowling balls crack?" has no
definitive answer....but lots of opinions. Temperature....too hot....too cold,
placement.....left in one spot too long causing a concentration of pressure,
the type of plastic used in the ball, the amount of curing time.  Oddly enough
most people do not say this happens from throwing the ball tooooo hard.  And
so those of us who use recycled bowling balls to make gazing balls will have
to put up with their capriciousness.  I now need to get back on the hunt for
another used bowling ball....which are as scarce as hen's teeth in La Paz.