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Old 04-04-2019, 09:54 AM
Shawn Everette Shawn Everette is offline
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Degassing inside paperweights

So I've been working on some new paperweight designs, pretty basic disk of color in the center encased, and have been having issues with bubbles appearing where the color is. Now the odd thing that's been occurring is that the bubbles start to appear as I'm flashing the piece down. No fuzz, no scuzz, while working it, but a film builds on both sides of the color as the center starts to cool. I've tried it with multiple colors (mostly reichenbach) with the same result.

I've had plenty of gathered bubbles disappear on me as a piece gets cold, but never anything like this. Clues?
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Old 04-04-2019, 02:23 PM
Eben Horton Eben Horton is offline
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Itís a vacuum. Cool it down in a more gentle way and I bet they go away. When you flash it, the surface is expanding and pulling away at the gooey core which causes a vacuum bubble to appear.
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Old 04-04-2019, 03:41 PM
Shawn Everette Shawn Everette is offline
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Makes sense. I've done these before, think I was using cristalica rather than studio nuggets, and it didn't happen. Also seems to be more frequent when I bother to punty the weight to clean up the pipe mark.
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Old 04-05-2019, 04:03 PM
Rick Kellner Rick Kellner is offline
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Gotta spin it into a selling point. Whip up a marketing spiel about thousands of little silver galaxies inside your universe globes. Proprietary technique, you know! Could wind up being your serendipitous paperweight accident.
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Old 04-05-2019, 10:27 PM
Jordan Kube Jordan Kube is offline
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Quote:
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Gotta spin it into a selling point. Whip up a marketing spiel about thousands of little silver galaxies inside your universe globes. Proprietary technique, you know! Could wind up being your serendipitous paperweight accident.
And then one day it doesn't work and you can't figure out how to reproduce it!
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Old 04-06-2019, 07:19 AM
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So, Collectors reserve! Limited edition! Signed by the artist!
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Old 04-06-2019, 09:31 AM
Art Freas Art Freas is offline
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Paperweight with patented space vacuum inside.
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Old 04-06-2019, 09:44 AM
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I just tell people that there is a little bit of New Orleans air and "magic" in each one!
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Old 04-06-2019, 10:30 AM
Eben Horton Eben Horton is offline
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Quote:
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I just tell people that there is a little bit of New Orleans air and "magic" in each one!
And maybe their grandma
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Old 04-06-2019, 11:52 AM
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And maybe their grandma
That's a different thread!
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Old 04-10-2019, 10:17 AM
Bradley Howes Bradley Howes is offline
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Jacob Willcox had an old piece of r-54 from chihuly's studio. He told me he was instructed to flash it before gathering to prevent bubbles from appearing later while working it. I don't know when these bubbles show up though. Maybe thats something to try?
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Old 04-10-2019, 10:28 AM
Shawn Everette Shawn Everette is offline
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I can always try, but I'm pretty thoroughly cooking it prior to gathering. I've gotten into the habit of at least heating once before gathering to cook of any dust from the marver or block skuz.
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Old 04-10-2019, 05:50 PM
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my mental jury is still out. Dust from whatever source is in my mind.
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Old 04-13-2019, 07:18 AM
Eben Horton Eben Horton is offline
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Quote:
Originally Posted by Pete VanderLaan View Post
my mental jury is still out. Dust from whatever source is in my mind.
Perhaps it could be from block carbon - I.e. blocking too dry. But I still think it has to do with rapid cooling.
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Old 04-13-2019, 07:57 AM
Shawn Everette Shawn Everette is offline
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I'd have more faith in the dust/carbon contaminate theory if the bubbles showed up after I gathered, not at the coldest point on the pipe.

I'm not really sure how to about cooling it slower. We've been flashing them down and not trying to speed it up with air or anything. Had the thought of blasting it with the torch. Next time we do them I might try to get pics/vid of them forming.
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Old 04-15-2019, 01:37 PM
rodman gilder miller rodman gilder miller is offline
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Much ado about nothing... it is little pieces of vacuum. Consider a sphere of glass with a tough skin which is hard enough to resist shrinking. Inside is an area which is still hot enough to move and contract. Surface tension will resist formation of a bubble, but once a bubble starts, it will grow.

There is a lot of residual stress in such a paperweight, but that is OK because if the weight is symmetric, the stresses act to temper the glass.

Much ado about nothing
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Old 04-15-2019, 02:08 PM
Shawn Everette Shawn Everette is offline
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Considering that unwanted bubbles are a bane of many a glassblower, I'd say it at least a little ado about something. I get the concept of what is happening, I'm looking for suggestions to prevent it. I've done this work before with different glass and not had anything like this. If it was as ubiquitous as hot glass inside cold glass makes a vacuum then it should be in nearly all paperweights.
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Old 04-15-2019, 04:48 PM
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Back when Lenny DiNardo was making his grall work with overlays and not getting the kind of bubble you suggest, he said "Scrub the shit out of it". That at the time seemed dubious but I would tend to give it a second look. Joints between interfaces are chock full of mysteries but gas is usually a gas and it's made from the materials around us. I'd try cleaning stuff a lot more religiously. It just won't be fun. I don't tend to think its coming out of solution. viscosity is possible. In making color rods, when we slowed down the cooling process, things got a lot better. Give it three slow cooling heats before the box.
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Old 04-15-2019, 04:49 PM
Dave Bross Dave Bross is offline
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Remember those bubbles that went into solution when you fined the glass?

Think along the lines of what might be bringing them back.

As for the variation between glasses?

Depending on formulation, some glasses can suck up more of the things that were in those bubs before they found their way into the liquid state...and then bring them back to visit when least expected. The chemical makeup of the gas in the bubbles will be different from one glass brand to the next too.
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Old 04-15-2019, 04:53 PM
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I don't tend to think that gas which is absorbed back into solution is going to constantly come back unless the valence has switched on the outer electron ring of two specific elements, Arsenic and Antimony. I don't see that temp/valence switch happening here.
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Old 04-15-2019, 05:43 PM
Dave Bross Dave Bross is offline
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Good point.

Could a high internal vacuum change the valence switch temp?
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Old 04-16-2019, 09:07 AM
Shawn Everette Shawn Everette is offline
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I can try scrubbing the frit, but it just seems unnecessary. It seems odd that the base glass is essentially having a reaction to the color when it is solid, and not when it is blown. Also, doesn't happen when the color is away from the direct center. I'm doing another batch this morning, try to see how many flashes it takes to get the center of the glassy pop.
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Old 04-16-2019, 09:29 AM
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Back when we were doing the color rod business when we made fluorine opaques, the glass drew from the furnace as a total transparent and struck as it cooled- very rapidly but you could easily see whether there were bubbles in the gathers. We made the rod, hung it up until rigid and boxed it.

The next day, I would take samples of colors and run them through the diamond saw on the vertical, sawing the rod in half like a pickle might be sliced and there, in the core, the rod was laced with huge bubbles, not a few, fifteen or twenty per rod like swiss cheese.

So I changed the technique and after the rod was formed, I heated it in the gloryhole three times just to the point of it slumping and then cooled it again. Three heats, three cools. Then, it went into the box.

Testing those rods yielded absolutely no bubbles at all. It needed to be cooled throughout.

It's your call.
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Old 04-16-2019, 11:44 AM
Shawn Everette Shawn Everette is offline
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So the batch I did today I got no irregular bubbles, despite not changing much about the way I flashed down. The main change was that I didn't punty any of them for clean up. One I'm going to cold work, but the other two I switched my axis before the last gather to get the face of the design oriented where I wanted, and poof, no bubble dusting.

This would make me think that it was a cold core and then reheating to clean up the surface after that was leading to the bubbles, not a hot core and cold surface.

I'm not sure if we can manage the switch prior the last gather for the main design my partner is working on, but so far the solution I've come to is don't punty the paperweight.
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