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Old 05-16-2015, 09:32 AM
Rich Arentzen Rich Arentzen is offline
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Color bubbles

Using color bars, what techniques are people using to avoid color bubbles, and what would be considered a reasonable and successful percentage of pieces without them?
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Old 05-16-2015, 09:45 AM
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Pete VanderLaan Pete VanderLaan is offline
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In rod, when opaques using fluorine are being made, you can see bubbles completely when the rod is being made before it strikes. The rod needs to be cooled rather slowly to prevent an outgas from the rod core.

Experience tells me that lots of bubbles in rods come from putting color in your color box hot. Micro fractures occur when rod is treated that way and they show later as bubbles. There are also bubbles in rods themselves as they are being made. Bubbles get introduced into pot color from the trailing glass from gathering rod and the more rods you make, the more of those bubbles happen. I find that the upper half of a pot is suitable for good rod and anything after that needs serious inspection. I usually turned the lower 2/5ths to frit and considered my self lucky.

Now galleries and stores? They're all different. I think it depends on size and location. Some are ridiculously so stuck on perceived defects that they can't see the piece at all. I have one that doesn't want light colored transparent glass because it's hard to photograph. I would not be happy paying for a color rod that had big bubbles in it. It's not easy to make them.
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Old 05-17-2015, 01:38 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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I think a lot of bubbles are caused by people trying to whack off a small piece from the end of a rod...it causes fractures that make bubbles. The german color rods have gotten a lot better over the years and Id say its not a problem with the color, its operator mistakes. The trick is to hit the rod in the middle and then the middle again etc until you get the size you want- it will make a clean perpendicular break every time and no fractures.
We try to preheat the rods a bit by putting them on top of the annealer for 30 minutes or so when possible but lots of times a 4-6 inch rod will go in "cold" and they dont fracture- if they do they blowup- maybe one in 50
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Old 05-17-2015, 06:08 PM
Eben Horton Eben Horton is offline
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Pete is right about cooling bar too fast when its made.. Riechenbach special black has a bubble to be found in about every 3 inches of it. I guess that is what makes is special. They are in there before you break it because if you are lucky, you will get lucky and crack it right on the bubble.

to avoid bubbles, i will be very careful about how i shape it before i put the starter bubble in the color... no rust on my marker or jack handles is a must, don't block it unless you know your color can take a blocking.. some colors will stick to the block. I always flash it right before i gather so the skin is warm.
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Old 05-17-2015, 06:38 PM
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Pete VanderLaan Pete VanderLaan is offline
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This is a repetition of something I've said before but it bears repeating:

When we used to make color, particularly fluorine rods, we would gather the glass three times and then roll the rod. Speed was important to profit. Fluorine opals are transparent drawn from the pot so we could see if there were issues. We would draw a perfect rod, roll and box it. In the morning, I took one of every five rods and ran it through a diamond saw vertically to see where problems might arise. Those rods had bubbles the same size as Swiss cheese in them.

So, I changed technique and once the rod was formed, we reheated three times which slowed our process down enormously. The diamond saw work revealed a flawless rod.

Kugler for a while made rod casting them and they all had a string of bubbles down the core and to this day I believe they were having the same problem I had. Glass demands that you be patient. It doesn't tolerate shortcuts.

Dan Fenton : "Glass remembers everything you ever do to it."

Sleep on Buddy.
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Old 05-18-2015, 04:49 AM
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Here's some things I have picked-up over the years that seemingly help prevent introducing bubbles in rods. If your rods have bubbles already, there's not much you can do about it other than pick them out once the glass is nice and soft.

Some of this stuff I learned from one of Lino's assistants for anyone that cares about that.

To preheat opals (I do this mainly with Gaffer white, and pretty much any other white, enamel, etc.), take your chunk of rod and place it in a ceramic coffee mug. Fill with water to cover. Microwave on high for 1.5 to 2 minutes. Use tongs to take from cup to color oven.

For ALL colors: when taking first heat in glory hole after picking-up out of color oven - don't turn the pipe/rod. I know it goes against everything you've been taught, and it takes awhile to get used to. Apparently, the slight temperature differences in the gh environment are enough to induce thermal shock as the piece rotates in the chamber. Insert it slowly and hold it perfectly still for about 20-30 secs. It'll sag, then you can turn. I know it sounds nutty, but I've had almost no instances of popping since I adopted this technique.
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