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More on stretching:

If stretched by dropping, Bullseye Opaque Thin seem to be OK, but if stretched flat on the shelf, it breaks shatters, and shatters the rest of the glass. Has anyone experienced this problem? What causes it? I have theories, but none of them make sense to me.

Understand "stretching" via a drop, but how are you stretching the glass on a shelf? And what is the layout (layers, glasses, decorations, etc.) and schedule(s)?

Hi Dairy,

if you could give a fuller description of your glasses used, your firing schedule, your layup/layout, and your process, I think you'll get better information.

warm regards,

Eric

Here is one example. Lay up is on one 10 X 10" piece of 3mm translucent white. The stack is a total of 12mm of 8 X 6" of glass. Many things are going on here, including travel, but the goal is to get the stack to stretch to the size of the transparent white.

I don't see the break or shatter. What is the white in the middle of the coloured glass?

Steven, this is not the thin opaque. It just shows my method of stretching. I don't have photos of the thin opaque failures, but they were stretched the same way. The design in this piece is trrips of factory glass, stacked like a plaid, and stretched out to 6mm in thickness. It is sandwiched between pieces of 3mm clear. The goal was to get it to stretch to the size of the base glass, with a finished piece being 6mm.

I guess I need a lot more information to understand what you are doing, as I don't see how movement of the kind you describe would lead to fractures on 2mm glass that don't happen on 3mm,.

It might claim to be 2mm, but it is thinner than that. I never took photos of the failures, but I did box them up to go back to Bullseye. It has probably already shipped.

To be clear, it only happens with yellows and piss greens. Other colors like pink, blue, and dark greens don't have any problem stretching. They like it, and become translucent, looking like a watercolor.

A thought:

Does Bullseye use the same annealing schedule for thin as for 3mm?

yes
and for 6mm

Hi Dairy,


There are many of us that've played with the stacking technique, which is a lot of fun. I've done a little of it, though not extensively; I was fortunate not to have the issues you're describing.

what sorts of schedules are you firing?

I notice the notes on your photo of a top-temp of 1450 deg. F. with a hold of 5 hours. Are you ramping up at 200 deg./hr., 300 deg/hr.? ,or maybe higher? If the cracking isn't coming from the ramp up, or the annealing schedule, nor because the spreading glass is sticking to the shelf as it crawls across, then it's perhaps a compatibility issue. But if it's all Bullseye compatible, fusing glass, then a 5 hour hold at 1450 (assuming it's the first, and not a repeated lengthy hold) shouldn't be too excessive and put any strain in the glass (assuming appropriate annealing sched.).

I've witnessed repeated high-heat firings (1600-1700 deg. F.) cause some compatiblity issues on some of my experiments several years ago. And I remember Bullseye had an issue with one of it's 'dense white' colors (I don't remember the number off-hand) a number of years ago when it was subjected to high heat working. It was fine at fusing temps, but the high heats, and repeatedly used at high temps, were the source of the problems (if I remember correctly, anyway).

If you use only Bullseye, and haven't accidentally slipped in a piece of spectrum, etc., then perhaps Bullseye may be the only source to determine the issue. Maybe an errant batch of glass? Or other factors we haven't thought of, yet?

Your schedules could help us trouble shoot, too.

warm regards,

Eric

Could your kiln wash be failing, allowing glass to stick and then break?

Again, without photos of breakage, full schedules, and other parameters like type of shelf, wash, etc., it's hard to tell what's going on.