Tempering glass

can be quite the challenge. It requires heating glass to avery high temperature and then allowing the glass to cool quickly.This alters the molecular composition of the glass in such a waythat the glass becomes up to six times harder than normal glass,but at the same time it is more brittle. One advantage to temperedglass (besides the extra strength) is that if tempered glass shouldbreak it crumbles into safe chunks rather than sharp andpotentially dangerous shards.

Instructions
1 Shape or drill any holes in your glass before tempering.once your glass is tempered it cannot be cut or drilled withoutshattering into small thumbnail-sized pieces.

2 Heat the glass you wish to temper to a temperature of atleast 600 degrees Fahrenheit in an oven or a kiln.

3 Remove the glass from the oven or kiln (carefully, usingtongs or a special paddle made for handling hot glass) and set iton a brick or cement surface and allow it to cool quickly byfanning it with cool (but not cold) air. It is the quick cooling ofthe outside surface of the glass that causes the molecular changesthat make the glass tempered. Allow the glass to coolcompletely.

4
Check to see if your glass has been properly tempered bylooking at it with polarized glasses and shinning light through it.Tempered glass will have patterns of shadows (sometimes called"quench marks") visible with polarized lenses.