# Air bubbles in glass



## kwalker (Apr 30, 2011)

I was thinking about this the other day; The air bubbles in the glass that we all either love or loath. Since that bubble is sealed, is the air inside of that bubble still original? Is it possible that an unbroken glass bubble has 120 year old air inside of it still trapped, or is it likely to leech out of the glass eventually because the surface is so thin?


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## cowseatmaize (Apr 30, 2011)

> Is it possible that an unbroken glass bubble has 120 year old air inside of it still trapped,


Yup, are you considering a chemical annalysis for the global warming debate?


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## cyberdigger (Apr 30, 2011)

I wouldn't think the bubbles have regular old air in them, considering they were formed in the 2000+ degree cauldron of molten glass.. they're probably filled with gases from impurities in the mix. In other words, you're unlikely to smell the 120 year old hot dog belch from the glass blower if you opened one up.. []


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## GuntherHess (Apr 30, 2011)

it would be the original air but the air wasnt that great in glass houses from what I have heard.


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## RED Matthews (Apr 30, 2011)

Well I have to get in here with some thoughts.  There are many sources of trapped air in early glass making techniques.  The batch mix is the biggest culprit.  Having seen glass batch mixed on a dirt floor and then melted in a crucible in a furnace, I can realize how trapped moisture can be a big cause of trapped air.  This was done at a modern glass plant in Marion, PA, to make some special bottles for a retiring glass maker.  The accomplished the early glass look in the bottles.

 I have some demijohns that have excessive trapped air bubbles.  The thing I don't know, is what type of mold material was used.  If the mold was made of a ceramic material, and I think that is what was used.  I have not been able to find any printed clue to what they might have lubricated the shell molds with.  I am sure there was something used that introduced the air bubble excessive quantity.

 In the early hand forming of bottles, the shaping of the neck and shoulders picked up a lot of air in the glass.  The folds and twist lines in those areas, show us a lot of stress was put into the glass to get it shaped.  It wasn't until the 1860s that most glass bubbles ceased to be in the bottles made.  This was also about when the patents of Sweeney, Mathews and Heartley; developed and patented the chilling of the mold iron castings, that the bubbles disappeared.  Their process change gave the glass industry a great change in glass making around the world.  The news of the effects in the cast iron mold cavity surface gave them better polishing ability, and the tight pure iron between the dendritic carbon rows gave the iron a reduced heat transfer capability.  This caused the bottle mold to maintain a hotter surface in the mold when the final blow pushed the glass to the mold cavity surfaces.  This made the glass flatten to a more uniform thickness and thus the glass lost a lot of its variable thickness in the glass bottle walls.  It is referred to as whittle, but it was really caused by the colder mold surfaces contacted in the final blow.  This application spread like wild fire with all mold foundries, and I am sure the people that got the patent didn't get much compensation for their solution to press ware molds.

 Some of them are neat and all - old hand made glass is just beautiful to my eyes.   RED Matthews


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## kwalker (Apr 30, 2011)

> ORIGINAL:  cowseatmaize
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> ...


 
 That'd be interesting if the air was natural. I'm sure there'd be some interesting results from that one...


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