Author Topic: Glass cracking  (Read 747 times)

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Offline gfirob

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Glass cracking
« on: April 17, 2012, 12:37:13 AM »
I have recently seen two different  pieces of heavy glass—a Gunnel Nyman piece with interior bubbles from a spiked mold, and an Ingeborg Lundin Ariel—with massive cracks in them, but no impact point, indicating they had been dropped.  And the pieces remained whole, cracks not withstanding.  The cracks don't seem to show on the surface of the glass.

What causes this?  Putting them in the dishwasher to dry?  Inherently different tensions within the glass layers?  An impact while being shipped, but while still wrapped (I have seen camera lenses smashed this way)?

Anybody else ever seen this?  Any ideas? 

rob


Offline ahremck

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Re: Glass cracking
« Reply #1 on: April 17, 2012, 03:17:34 AM »
Any thick glass is at risk if it has a temperature gradient.  The most likely reason is that people put them into warm soapy water to wash them.  Even such a slight gradient generates huge internal forces in the glass - hence a crack.  You see it very often with jugs where the handle joins the jug itself.  The thick handle generates the force to crack around the join in the jug proper.

Personally, we lost a lovely large Bohemia crystal bowl when my wife was about to put together a friut salad.  She had some frozen passion fruit - very little indeed - and unfortunately dropped it into the bowl first.  almost immediately came the load "crack" sound - vale a lovely thing.

Sometimes the crack is restricted to only part of the thickness - I kave a Flygsfors Kedelv bowl where only the topmost layer is cracked.

Ross
I bamle all snileplg eorrrs on the Cpomuter Kyes.  They confuse my fingers !!!


Offline Ivo

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Re: Glass cracking
« Reply #2 on: April 17, 2012, 05:56:18 AM »
It happened last week to a Riihimaki vase i had just bought - perfect in the shop, fully cracked base when unwrapped. And not even due to temperature diffrences.
Some time ago i had a footed vase standing on a top shelf which spontaneously selfdesructed and jumped down, wedging itself in the parquet flooring.
These things happen.....
Ivo
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Offline ahremck

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Re: Glass cracking
« Reply #3 on: April 17, 2012, 06:57:00 AM »
That has not happened to me with thick glass - but a set of glasses I bought c. 1980had a tendency to crack off (very neatly) the top 7mms or so.  I attribute that sort of behaviour to either a design fault or more likely the annealling process is flawed.

Ross
I bamle all snileplg eorrrs on the Cpomuter Kyes.  They confuse my fingers !!!


Offline glassobsessed

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Re: Glass cracking
« Reply #4 on: April 17, 2012, 01:02:03 PM »


Offline gfirob

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Re: Glass cracking
« Reply #5 on: April 17, 2012, 03:49:23 PM »
Thanks.  I will never approach a piece of glass again in the same way.  Some of these very thick ones have a lot of mass and now I have to think of them has hand grenades...

Rob


Offline flying free

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Re: Glass cracking
« Reply #6 on: April 17, 2012, 07:42:20 PM »
Having just read this and John's linked post I feel sick  :o I have so much glass in the sitting room and some of it is very big lumps of glass - I can't bear to imagine what 6lb of glass might look like exploded, or the damage it could do.   I'm just off to swap my studio pottery into the kitchen at least.
m


Offline glassobsessed

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Re: Glass cracking
« Reply #7 on: April 17, 2012, 10:28:19 PM »
The exploding thing is genuinely rare, not going to lose any sleep over that one and I am surrounded by the stuff.  I worry about me, I have chipped, cracked and broken loads of bits. I knocked a big perfume bottle over the other day and snapped the stopper in two. :'(

If I started sleep walking that would be problematic. ;D

John


Offline flying free

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Re: Glass cracking
« Reply #8 on: April 18, 2012, 03:14:41 PM »
mm, yes on that basis,  well let's not discuss - I am responsible for breaking two of my most expensive pieces.  OH did put a very old tazza that I' d used at Christmas in the dishwasher and when I got it out it was in two pieces  ::)
m


 



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