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Air Bubbles


Chordus
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Air bubbles are fairly common in certain machine-made marbles, and I've seen them used a lot in contemporary marbles as well. I'm a little unsure of how they can exist without cracking the marble, though. Does air have a similar CoE to glass? Or is there something else going on here?

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I might be able to help as I like to include little air bubbles in some of my marbles I make. As you can see in this pix, I put a spread of bubbles inside the clear viewing dome. If one follows the 15% rule with trapped air, usually there isn't a problem with tiny bubbles. The COE isn't a concern but the percentage is. Another factor is how close to the external surface is the bubble. Depending on the size of the mib, the closer to the surface the bubble is the more chance of making a pin prick or little dent and possibly breakage.

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The CoE of air?

I'd assume it was significantly different from glass.

However, I'd also assume that any pressures and strains from the air on the glass are negligible. That as the marble cooled the air would easily compress into whatever space was available without straining the glass around it.

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Also occasionally the glass itself boils under the intense heat when it's melting point is exceeded to highly causing bubbles to form in the interior of the marble.

RSC is correct. In machine-mades - bubbled glass is over-heated glass.

Glass heats and cools much slower than air. That does not mean that the glass will have unhealed stress in it. Some contemporary makers create pieces with large air inclusions in them:

IMG_3416.jpg

IMG_3417.jpg

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Alan, that's the type of controlled pattern I mean. Is it a trade secret or how exactly does the bubble make a non-bubble shape. Almost looks like a "sprue" on the B. Those are awesome marbles by the way.

I have seen Mark's tool for air traps - but don't know what he considers a trade secret. I think the fine nuances of the tool(s) he uses ARE unique to Mark. I had a one-hour conversation with him n just this subject and how he fine-tuned the tool and technique to achieve the level of perfection that Mark expects. He goes through quite a refinement process to get a piece that he is willing to put his name on. Some of his designs like the Comedy and Tragedy theater mask air traps are very problematic to create.

Geoff Beetem makes some quite different air traps that are very nice as well.

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