In message , Huge
writes
Nickel suphide inclusions.

http://www.glassonweb.com/articles/article/330/

Makes toughened glass shatter spontaneously.

Astonishing really, a single 100um particle changes phase after 10 years
and an entire window comes showering down from the 11th floor. Beats a
butterfly beating its wings in China causing storm in Harrogate.



--
bof at bof dot me dot uk