Lisa - Did you counter-enamel the back of the piece? That’s the first
thing that I would look to because stresses can easily cause cracks.
Secondly, it appears that the COE may be different between the two
colors of enamel - that may be a cause. Thirdly, you are working on
metal clay which is a bit more porous than sheet metal - are you
absolutely sure that you got all chemicals, etc out of the silver
before putting on the enamel? I would remove the enamel and start
again. The easiest way to do this is to heat the piece in the kiln
and then drop it into icy water. Instant cracking off of your enamel
(you will probably still need to do a bit of hand work - but it is
much faster than drilling the whole thing out with a diamond drill).
Good luck.
Sandi Graves, Beadin’ Up A Storm
Stormcloud Trading Co (Beadstorm)
http://www.beadstorm.com
Saint Paul, Minnesota USA
651-645-0343