Today I was stunned by this connection.
Its not new, been a problem known from about 2003 apparently.
My Son tried to buy a spark plug today. Minors cant (along with paint spray cans). WTF !, below is the reason.
If you crush a spark plug, and casually toss the resulting white ceramic shards at a windscreen, it explosively destroys it
.
Its become a huge problem with vandals and car thieves.
Apparently, spark plug ceramic is harder than glass, so on contact causes a small crack and a stress release that blows the window to bits.
There are many utube videos that show this effect, its stunning.
Who would have thought of trying this to start with
.
Im guessing this would only occur with stressed glass, not game to test it.
Edit:
http://en.wikipedia.org/wiki/Ninja_rocks