Encouraging Devitrification

Better a Finn who speaks excellent English explain it for Brian, rather than Brian himself.

Reply to
db
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Those are Brian blanthorn's notes. According to him devit grows most when the glass temperature is such that it starts moveing (f.ex. slumping) but is not yet very liquid. As I understand it happens when the molecular bonds are breaking but the glass is not so hot some of them cannot combine back to acrystal form.

Devit glass is crystalline, it has different COE, according to Brian.

-lauri

Reply to
Lauri Levanto

Yes, my notes are translations of Brianese.

-lauri

Reply to
Lauri Levanto

To my understanding from a conversation a long time ago with Gil Reynolds, the glass is at a temperature where it wants to move,(perhaps the surface?) but not so hot that it is physically possible for it to do so. Like being right on the edge, 10 more degrees and it does move.

If you have a piece of glass in a torch, and it is easiest to see with clear, and you apply stress in opposite directions on the rod, such as a twist motion, and the glass is not hot enough to twist, you will see devit form at the stress area of the twist., just before it moves.

Hence why I like to fire fast, but have never, ever had a problem with devit, and I rarely ever flash vent when fusing, and never when bending.

Reply to
Javahut

Nah. You aren't smart enough to be anything more than a minor annoyance at best, and a laughingstock all of the time.

Just as most people wonder about the insane obsession you have for self-promotion. As they say in Texas about people like you: "Big hat. No horse."

Reply to
Moonraker

Somewhere else in this thread, somebody said, ""Do you know anything at all about kilnforming - or just make up crap to start a fight?"

Reply to
Moonraker

. . .

interesting, that observation seems to match with my theory above. The twisting applies some more force to break the molecular bonds, and permits rearrangement to chrystals.

and I rarely ever flash vent when fusing, and never when bending.

That is a good point. When bending there is that state present when the glass is "twisted" by gravity and not yet truly bending.

Anither question: Can someone explain why the devit is most common on the air surface. The uncleaned glass, as Brian said, has nuclei for chrystal forming on the surface. But it has also on the underside.

As a newbie I slumped bottles. Once I had a not so clean clear bottle that develope devit. I refired it to grow the devit (the situation of the originator of the thread) and got about .5 mm snow white devit. I cut it and saw that the devit has grown not only outsides but also on the internal surfaces in the middle of the sheet. Unfortunately I do not have the test piece left.

The dirt was a clue, but I never really understood what happened there. Devit growing in the middle of double layered glass.

-lauri

Reply to
Lauri Levanto

The devit zone is normally considered to be 1200-1400, the longer the glass is held in that range the more likely that it will show devit and the more devit it will show. The exact range depends on the glass, of course. If a kiln is opened and the temperature dropped quickly, it will normally bounce back, the amount depending on the materials of the kiln. An all frax kiln will bounce less than one of insulating fire brick while one with thick kiln shelves or a solid floor will bounce even more. It may be necessary to open the lid a couple of times to get the temp down. Re: another reply. A thermocouple measures the temperature of the end of thermocouple, not the air temp. The temperature of tip will be a combination of radiant heating from the walls and convective heating from the air moving heat from the walls and floor.

Reply to
Mike Firth

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