Glass Discussion & Research. No ID requests here please. > Germany

Conchoidal fracture (bruise) on Greta Vase

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paradisetrader:
I think the fault / damage seen on this large Greta Vase is a burst bubble.
I'd like to confirm that and make pics permanently available for future reference at the Glass Queries Gallery generously provided by Anne (Yobunny) http://glassgallery.yobunny.org.uk/thumbnails.php?album=37

Something Frank said in an earlier thread was in the back of my mind when I thought this but reading it again now I am unsure.
In topic Factory Faults Frank said

--- Quote ---Bubbles near the surface easily crack and sometimes a hole to small to see even with a glass. Water has much better eyesight and has no trouble finding its way in where it evaporates when warmer with some of the vapour leaving the way the liquid got in. In doing so it leaves behind a deposit of the heavier minerals giving the whitish frosted appearance."
--- End quote ---

This bubble is entirely enclosed within the glass. No crack can be felt on the surface only a very very slight bump ...possibly. I guess there may be tiny cracks too small to see or even feel.  The frosty area around the bubble seems to me more to do with internal shattering of the glass rather than mineral deposits. The frosy area is not a perfect circle around the bubble.

Frank also said

--- Quote ---There is no way to tell if a crack in a bubble was caused during cooling, annealing or after the event.   
--- End quote ---
I'm not sure exactly what it meant by this but if still refering to burst bubbles then I have the stongest feeling that this particular one was done after manufacture ....probably by me, by leaving the vase on a sunny window still, possibly after washing it.

The vase is destined for a place where it will be much appreaciated desipite this burst bubble which only shows from one side.

Connie:
JMHO Peter - If the bubble is still completely enclosed by glass then it has not burst.  It has the potential to burst as Frank described so moving it where it does not undergo aburpt temperature changes is a good idea.

A burst bubble will either have rough edges - the whole top of the bubble shattered off.  OR - it can have a small hole on 1 surface as previously described.

Frank:
The hole can be microscopic and undetectable.

Connie:
Ok Frank  I revise my opinion.  The bubble has not burst in such a way that it is visible to the naked eye  :lol:

paradisetrader:
So it this is a burst bubble then ?

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