Vitrigraph bubbles and craters

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Lee Sorg
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Joined: Fri Feb 20, 2015 1:15 am

Vitrigraph bubbles and craters

Post by Lee Sorg »

I'm having bubble and crater issues with vitrigraph. I am using vitrigraph to create abstract designs, and in the initial full fuse of the vitrigraph to the glass sheet I am ending up with small bubble/craters in some places - usually at a place where the vitrigraph stringer is fatter than the stringer before or after that place. The size of these bubbles/craters range from 1 to 3 mm (sometimes they are bubbles and sometimes they are collapsed craters). My guess is that there is air trapped in the stringer at this place and it can't escape. I've adjusted the time for the bubble soak stage from my normal fuse schedule, but I'm still receiving the same result. My most recent adjusted schedule is: 300/1100/0 - 150/1240/60 - 400/1440/10 - AFAP/960/60 - 150/700/0. The kiln is Evenheat GTS 2541-13. I have been fusing two vitrigraph stringers, Red Tomato and Black, on separate glass projects and am having the same bubble/crater issue with both. Assistance with this issue is appreciated.

Thanks, Lee
Brad Walker
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Re: Vitrigraph bubbles and craters

Post by Brad Walker »

Got a photo?
Lee Sorg
Posts: 8
Joined: Fri Feb 20, 2015 1:15 am

Re: Vitrigraph bubbles and craters

Post by Lee Sorg »

Hi Brad, thanks for your help on this. I've added three photos.
Photo A (green), done about a year ago, shows what happens on my initial full fuse firing of vitrigraph to a sheet of glass. This kept occurring, so I stopped at that time trying to make vitrigraph work. But, I like what’s possible with vitrigraph and know other use it. I haven’t read or seen others discuss this issue, so I'm not certain why this is happening and it may be as simple as a result of the schedule that I’m using. Photo B shows a recent piece, this one is subtle bubble, but often the subtle bubble becomes a problem on the next full fuse when I add design elements to the piece. Photo C shows the craters that opened up on the second firing — I’ve cleaned out the holes and will fill them in with fine frit of the same color and fire again — this does not always work out well — the color isn’t always a perfect match and ends up looking like a patch job. Ideally, I want to work with vitrigraph and not have the bubble/crater issue do deal with at all. Thanks again, Brad, I appreciate your feedback.
Attachments
Photo A.jpg
Photo B.jpg
Photo C.jpg
Brad Walker
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Re: Vitrigraph bubbles and craters

Post by Brad Walker »

Glad I asked to see photos. Before you posted them, I had thought you were talking about bubbles trapped between the stringers and the glass underneath. But from the photos it looks like the bubbles and craters (which are popped bubbles) are actually in the stringers themselves, not in the area between them and the glass. That would suggest the bubbles are being created in the process of making them in the vitrigraph kiln, then becoming more noticeable during the subsequent firing. You haven't talked about how you make the stringers, but I do know that if you fire the pot too quickly you can get trapped air bubbles in the stringers. Is there any chance that that's what's happening?
Lee Sorg
Posts: 8
Joined: Fri Feb 20, 2015 1:15 am

Re: Vitrigraph bubbles and craters

Post by Lee Sorg »

I'm certain there is air in the stringer. I guess was hoping that a longer adjusted bubble soak in the full fuse might move the air out completely, but it sounds like that's not the solution. To create the vitrigraph, I use the Olympic HOTSIE P6. I set the dial to 4 until it reaches 500 degrees. Then turn it up to 6, till it reaches 1000 degrees, then turn all the way to High, till it reaches 1500. I then back off and adjust it up or down to keep it 1500 and then begin pulling. Perhaps the glass needs to get hotter before starting the pull, or maybe the speed at which I'm pulling the stringer out of the kiln is too fast? Is the answer completely in how I'm making the stringer or should I make an adjustment in the full fuse bubble soak as well? Sorry, I know that's a lot of questions.
Peter McCarthy
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Location: Cambridge, MA

Re: Vitrigraph bubbles and craters

Post by Peter McCarthy »

The bubbles are in the stringers, so I think you need to lessen the bubbles in that firing. It doesn't look like you have a bubble soak in you vitrigraph firing, and that's very important. I soak for 2 hours at 1225 when I'm pulling cane. I don't make stringers, so I'm not sure if a soak that long is needed for them.
Lee Sorg
Posts: 8
Joined: Fri Feb 20, 2015 1:15 am

Re: Vitrigraph bubbles and craters

Post by Lee Sorg »

Thanks Peter and Brad. Sounds like additional time in the vitrigraph bubble soak stage should solve the problem.
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