Ceramic belts and tempered glass

[J.Marsillo]

A while back I sharpened some of my wifes kitchen knives ( Crappy stainless ones ) on the KMG, using ceramic belts.I brought them in the house and rinsed them off in the sink,the only thing in the sink was a glass pot cover.After I shut off the water the tempered glass pot cover shattered.

This must be the same affect as the 'ol spark plug insulator on the car window.That or I got some hard water

 

[sunshadow]

if the ceramic media in the belt scratched the tempered glass lid, and it had been building up stresses from thermal cycling

<OH NO I SAID THERMAL CYCLING NOW I"M GONNA GET SUED! :O>

crack propagation in glass is accelerated by water, at least according to an article I read some years back (I believe it was in Scientific American but I could be mistaken) something about the interaction of dihydrogen monoxide and silicon dioxide where each preferred an atom of the other at the leading edge of fracture. Glass is a very interesting state, my chemistry teacher in High school called it a supercooled liquid, it tends to want to store fractive stresses as tension, then when something causes it to let go after it has absorbed a lot it can be spectacular (ever break an old pyrex beaker, think millions of tiny razor sharp shards! I broke one in my darkroom, and still occaisionally find little bits)

-page

 

[mete]

The best glass to take heat and cold is the Corelle dish glass which has zero coefficient of thermal expansion. Pyrex will not take thermal shock, been there done that !

 

[fitzo]

Interesting read on Pyrex: http://en.wikipedia.org/wiki/Pyrex

I was somewhat surprised at your comment about Pyrex's inability to take thermal shock, mete, as we frequently subjected glassware in the lab to thermal high-stress situations . The very name is derived from it's abiility to tolerate flame.

Made more sense once you read that Pyrex isn't "Pyrex" all the time, especially in the kitchen.

 

[mete]

Wasn't aware of the soda lime vs borosilicate problem. My experience was putting a 'pyrex' glass cover into a sink that had drops of water.

 

[fitzo]

I had no idea, either, mete. It explains why a lot of crappy import glassware we got used to specifically say "Pyrex brand" instead of Pyrex. It wouldn't tolerate the rigors of use we'd put old Corning stuff to.

 

[J.Marsillo]

So it wasnt the belts? Good now I can tell my wife to stop with the stink eye every time she uses her lidless pot

Of course there had to be a mention of pyrex and crack-cocaine couldnt they leave that out.....