Encouraging Devitrification

Hi, I am doing some fusing work that is devitrifying unevenly (some bits scratchy, some glossy)... I have tried the 'homemade' borax devit solution, but it doesn't seem to work with this glass... My current idea is to promote full-on devit across the entire piece. Nothing massive (I don't want it to look salted), just a fairly even sandblasted look.

Is anyone aware of any way to promote even / mild devitrification? Thanks, Andrea

Reply to
bliss3333
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Curious about what glass you are using and what your firing schedule is?

and to answer your question, unfortunately I have spent time trying to not have that happen, and I use a white matte paint from Reusche to even things out when that is the kind of look I want...Have a number somewhere if you want it...

Reply to
Javahut

Here is my firing schedule --

ramp up at 750 / hr to 1000 deg. soak for 10 minutes ramp up to 1450 deg. soak for 12 minutes crash cool to 1000 deg. soak for 15 minutes slow cool to room temp.

I am only doing small jewelry pieces, so they don't require very long in the kiln. I am using a variety of glasses -- some old, some new, some mysterious. The 'partial' devitrification seems to be occurring mostly with the 'motley' glasses... very annoying. I think I am going to try again with a stronger borax solution...

Thanks again, Andrea

Reply to
bliss3333

Don't waste your time. Mottled glasses are not designed to be fired after initial rolling and "striking" as are Stipples. the chemical content and silica levels are the reasons the crystals are forming. That is what the glass is designed to do when manufactured. Striking it when rolling, the end process before annealing, is what "forms' the mottled rings in the glass, crystal formation in the opal. The more you fire it, the denser it gets, also.

The following instructions are to be used at your own risk, but It just may work for you with mottles...all statements from here down are my own opinion. If you don't agree. fine, you have that right. As I have to express mine. Mine are based on having done it.

I have no idea what kiln you are using and what the capacity of it is, as far as ramp speed, but just for kicks, and try it with glass pieces that don't mean anything. Approach it as a test...as I would, because I fire darn few mottled glasses, and at fusing temps, none that stay mottled, but nearly none, (Lins is an exception) that denitrify.

I am assuming you are using small glass pieces as in jewelry, they should not blow apart at rapid ramp settings, and try it with mottles so you can see if it will work with the glass you want to use later....

I believe with small pieces,such as jewelry, there is no need to soak at different temps, and absolutely no need to go slow. So "Hot Rod" fire it All Temps are F.

ramp at 1200/hr,(60 deg/ min) straight up to 1450-1475, depending on the look you want. at temp, 1450 -1475, Shut it off, flash vent to 1000 and shut the lid and walk away, don't peek until tomorrow.

This assumes you are using a firebrick kiln, Evenheat, etc., not a Denver fiber blanket kiln, if you have one of those, you have to set the controller to do those things that fast. or slow, as to fire down anneal.

The idea is go thru the devit range, 1275-1325, as I call it, quickly, as fast as that kiln will go.

I have done an alternative schedule, that depends on a fast, hot, kiln.

1200 deg/hr to 750degF, where you go full on, as fast as the kiln will go. when you do this you will have to watch the peep hole, because you may have to go 25-50 deg hotter because the glass will need the extra temp because of the shorter time it is up there.

Play with it, but in general, Mottled glass was never and is never designed around being fired.

Reply to
Javahut

Actually, when I said 'motley' glass, I meant no-name and remaindered glass (as opposed to 'mottled')... However, I will still try out your suggestions and let you know the results... Thanks again, Andrea

Reply to
bliss3333

Really? Geez, just when I thought it was done to "stop the event that was currently taking place." I find it is done to AVOID DEVIT? I DON'T THINK SO DIPPY.

Reply to
Javahut

Other way around, numbnutz.

Rapid heating once past the upper annealing temp on up to the work temp prevents or minimizes devit. So a slow ramp UP "might" encourage devit...except that devit is more a function of the composition of the particular glass itself and not time vs. temp.

Why don't you take a big long shut up?

Reply to
Moonraker

remaindered

Why? Little toy boat sales sinking? Need something to copy to bolster your cash flow now that you've gotten busted for your kiln sales scam?

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Reply to
Moonraker

remaindered

You really are an ignorant twit.

It would be safe to say that Java has bent and fused more glass just this past week than you have in the past year. He's forgotten more about stained glass than you ever knew.

He could WRITE the book on kilnforming...if he weren't so busy making money actually DOING the glass work instead of posturing like you do.

Reply to
Moonraker

Price is one thing. Delivery is quite another. Having to deal with a lying asshole like you is still another.

Anybody who wants to check, can log onto most of the other glass forums and see how many compaints there are about VAG.

Reply to
Moonraker

Plenty...and I have no need to be bragging all over the web about it. Those who "matter" know exactly what I do. You, sir, don't matter. Not to me, not to any real glass professional.

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Reply to
Moonraker

That's your best argument, eh? You couldn't refute a single statement, so you obsess on something totally irrelevant, like somebody's screen name? Go f*ck yourself.

Reply to
Moonraker

Actually, avoiding devit is exactly the reason for crash cooling, no matter how much you don't like Dennis. Stopping movement of the glass could be done simply by dropping the temp a hundred or two degrees, crashing way down to 1000 is to get through (out of) the devit zone as quickly as possible.

Reply to
Mike Firth

Where is the "Devit zone"?

Flash vent to 1000 (assuming a firebrick kiln), and close the lid, what happens?

Reply to
Javahut

Ooohhh! Ooohhh! I know! I know!

Reply to
Moonraker

Why don't you post a link to that particular thread? Oh, and feel free to post any other links to comments from your admirers. It shouldn't take you too long to round those up.

Reply to
Moonraker

Um, Ive always done that,,, throw me a bone?

Liam

Reply to
Liam

A brick kiln and a mullite shelf are great reservoirs of heat.

"Flashing a kiln only lets hot air out. The bricks and shelf are still way hotter than the air after the flash. The pyrometer only measures air temperature. Watch the dial when you flash. As soon as the lid is closed, the needle begins to climb right back up. The cooler air is re-warmed by the stored heat in the bricks, shelf, and to some extent, your glass."--from "All I Know About Thermodynamics" by Yogi Berra.

The conventional wisdom now seems to be that rapid cooling of elements and bricks is deleterious to the kiln's life.

Reply to
Moonraker

You are right flashing a brick kiln bounces when lid is closed. Flash again and it bounces less. Bouncing itself is not necessarily harmful for the glass. It may be for thin glass. For a thick casted piece with huge thermal reserve you can cool the surface to near strain point, and remove some heat from the surface, the bouncing then accelerates heat movement toward surface within the glass. The time saved is not much compared to total cooling time.

To encourage devit "The devit guru" Brian Blanthorn recommends dirty glass. Devit starts easier from a seed. dirt is good seed. Devit grows faster when the glass is about moving both way up and way down.

Finally devited glass is not compatible with the same base glass.

-lauri

Reply to
Lauri Levanto

Please tell us more about this? I'm not understanding exactly what you are saying?

Reply to
Moonraker

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