Re: Why will a pebble of spark plug ceramic shatter glass?

You need to understand the nature of automobile glass which is 'tempered' 
and so requires very little force to literally 'explode'.  The ceramic 
chip not only provides the needed energy to initiate the process, it also 
does so without much sound energy being formed.

Layers of plastic - laminating- is used to prevent the 
shattered pieces from leaving each other.  

You can research this using Google as well, and the following webpage was 
useful for me
 http://priuschat.com/index.php?showtopic=10888