Topic: Aging glass

[oldglassman]

Hi ,
            yes I did read the link but my comments were with regard to the old wife's tale of window glass slumping not whether glass was a supercooled liquid or whatever , that I leave to the scientists among us ,also noticed this at the end
 " In any case, claims that glass panes in old windows have deformed due to glass flow have never been substantiated.  Examples of Roman glassware and calculations based on measurements of glass visco-properties indicate that these claims cannot be true"

so thought I would add my tuppence worth from the antique drinking glass side of things .

cheers ,
  Peter.
 edited to add  Maybe M your comment was for  aa's post and not mine !!!

[flying free]

No, I was just wondering whether you were querying the article.

From a science point of view, I like the article as it can be read to say that we have Liquids, Solids, Gases .... and Glass  (edited later to add - err, I said this with humour so please, no quoting that comment in future anyone who might be reading this)
and AA yes, I agree, for me that would make it 'super-cool'
m

[oldglassman]

Hi ,
               Nope i have no problem with the article at all , as said I would leave those comments to the experts my comments were purely around the "old wifes tale" of window slumping,

cheers ,
          Peter.

[aa]

This article referenced in the other one is also worth a read http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/windowpane.html

[Ivo]

The simpeler explanation of window panes being thicker at the bottom than at the top comes from a glazer who explained that when you mount the glass in the cames, you make sure to have the thickest part of the glass towards the botom. This gives a better weight distribution and added stability.

As for glass decomposition:
A calcium oxide deficit keeps the alkalis water soluble. Damp surroundings or humid storage may hydrate the salts and bring them to the surface. The result of this ‘weeping’ is sticky to the touch, has a sharp salty taste and smells strongly of vinegar. When dried out, the leached alkaline may form a crust: the first stage of disintegration. The second stage is crizzling, a network of fine cracks in the glass. Flaking is another appearance. The final stage is full disintegration: the glass falls apart like sugar. Glass is archeologically (but not geologically) speaking a stable material and devitrification is a natural process that occurs in all siliceous materials – including  flint and obsidian. All glass eventually falls victim to devitrification – though it may take a long time.

[Frank]

And of course in time everything turns to dust until a new Universe comes into being and allows glass to be re-invented once more. And with the rate of new planets being found in the habitable zone around stars, how long before we find another civilisation based on glass. Or even a glass planet