Re:[Vo]:2 Modes of the FPE

[a.ashfield]

Someone asked about crack formation.  What work I have done was to 
prevent them rather than make them.

Basically you heat the object up and then cool the surface sufficiently 
rapidly that a tensile stress is created that exceeds the tensile 
strength of the material.  Much easier to do with non ductile materials 
like glass.
Glass is rather strange.  Even if you make a crack free surface, contact 
with anything from dust to say touching with a paper handkerchief will 
cause cracks.  A typical glass tumbler has 70,000 cracks per sq.cm.  So 
polishing might also be a method.