Why would annealing cause devit?

[Anne Londez]

Originally Posted by Lyssa

I took a look at them and I wanted to say thank you for the links. This really makes me want to figure out for myself what the best annealing schedule is. I feel the need to either go back to university and get a materials science degree or spend the next few years testing different annealing schedules with different glasses, combination of glasses, sizes of beads, etc.

Too many variables!!! LOL

True but there is one way to overcome that issue: try an annealing schedule that is overkill from the beginning. Annealing schedules are well documented for fusing and your pieces are not bigger than fused pieces so base your schedule on the one for a small fused piece of about the same thickness. Bullseye's info is very useful, it just needs to be adapted to the actual annealing temp of whatever glass you're working with.

There is somewhere on the net a program that was made by glass scientists to modelize the annealing curve of a piece of soft glass depending on its shape and size... unfortunately it's in French. It's a modelization that's fairly accurate for larger pieces in my experience and one interesting thing it shows is that for tiny pieces, there is a minimum annealing time that you can't go under. For Effetre, that's around 25 min per cm of thickness for a round bead (under 1 inch) at the lower end of the annealing range. And there is a minimum cooling rate between the annealing point and the stress point that you can't go under either, which is roughly 1F per min.

[Lyssa]

Last night's annealing convinced me I need to get a digital controller. Not like I wasn't convinced before, but last night's batch actually lost some beads. First time for everything.

Originally Posted by Anne Londez

True but there is one way to overcome that issue: try an annealing schedule that is overkill from the beginning. Annealing schedules are well documented for fusing and your pieces are not bigger than fused pieces so base your schedule on the one for a small fused piece of about the same thickness. Bullseye's info is very useful, it just needs to be adapted to the actual annealing temp of whatever glass you're working with.

There is somewhere on the net a program that was made by glass scientists to modelize the annealing curve of a piece of soft glass depending on its shape and size... unfortunately it's in French. It's a modelization that's fairly accurate for larger pieces in my experience and one interesting thing it shows is that for tiny pieces, there is a minimum annealing time that you can't go under. For Effetre, that's around 25 min per cm of thickness for a round bead (under 1 inch) at the lower end of the annealing range. And there is a minimum cooling rate between the annealing point and the stress point that you can't go under either, which is roughly 1F per min.

[LarryC]

Originally Posted by Lyssa

Last night's annealing convinced me I need to get a digital controller. Not like I wasn't convinced before, but last night's batch actually lost some beads. First time for everything.

Good call. Not sure you can ever achieve a sufficiently smooth transition through the critical areas without one.

[PittsGlass]

I think what happens is that people want a conservative schedule that allows them to feel that they are getting the "most" annealing possible. They also want to cover a range of sizes in one program. Kilns, even with digital controllers have a swing in temp. Depending on the kiln it could swing up to 40 degrees in either direction, giving a range of almost 80 degrees. These hotter temps try to account for that in the programs.

[Lisi]

Whoa...you mean all this time (nine years) I've been making beads and the annealing temp for Effetre is 900F or below??! This is the first I've ever heard of this! Also the first I've heard of Effetre softening at 960?? I guess I've been lucky because I anneal mine on the mandrels and they have never wonkified out of shape.

Lyssa, now you aren't the only one who is confused! Damn...back to more research. sigh...

[Damselfly]

Lisi, as I understand it, I think what people meant by saying the annealing temp of Moretti is 870F, is that's the strain point at which all the molecules line up permanently. Depending on how much heat you lose when you open and close your kiln to add more beads, you wouldn't want to garage at that temp while you're working.

[Lyssa]

Originally Posted by Damselfly

Lisi, as I understand it, I think what people meant by saying the annealing temp of Moretti is 870F, is that's the strain point at which all the molecules line up permanently. Depending on how much heat you lose when you open and close your kiln to add more beads, you wouldn't want to garage at that temp while you're working.

And therefore, Damselfly, if you're batch annealing and not opening and closing the annealer constantly, you don't really need to spend any time soaking above the annealing temp. Is that correct?

[Lyssa]

That's exactly my point, Lisi. There appear to be "too many stories" for me to be able to know which one is true.

Originally Posted by Lisi

Whoa...you mean all this time (nine years) I've been making beads and the annealing temp for Effetre is 900F or below??! This is the first I've ever heard of this! Also the first I've heard of Effetre softening at 960?? I guess I've been lucky because I anneal mine on the mandrels and they have never wonkified out of shape.

Lyssa, now you aren't the only one who is confused! Damn...back to more research. sigh...

[Damselfly]

Originally Posted by Lyssa

And therefore, Damselfly, if you're batch annealing and not opening and closing the annealer constantly, you don't really need to spend any time soaking above the annealing temp. Is that correct?

I would say Not Exactly, for the following reason:

Once they're cool, the molecules are in a fixed arrangement. If you only go up to 870F (the temp at which they become fixed), then you're not really allowing them to change or to relieve any stress that might be there.

I think you want to go higher so the molecules are a little more elastic, and soak there long enough to affect the entire bead, then go down to 870F (and hold) so that the molecules can become fixed once again.

FWIW - I've done some reading, but I'm certainly no expert on this.

[Anne Londez]

Originally Posted by Damselfly

Lisi, as I understand it, I think what people meant by saying the annealing temp of Moretti is 870F, is that's the strain point at which all the molecules line up permanently. Depending on how much heat you lose when you open and close your kiln to add more beads, you wouldn't want to garage at that temp while you're working.

Sorry but no, it's the actual annealing temp that's given by the actual manufacturer. I can copy the Effetre catalog if you don't believe it. The strain point is way below that.

[Anne Londez]

Well I actually have the Effetre catalog scanned on my computer so here is the relevant page together with a close-up.

[PittsGlass]

Damselfly is correct IMHO. The more stress that could be accumulated in the design or thickness, the longer it needs to have free molecules, and the slower it needs to cool through and past the strain point. I would never suggest "minimalist" annealing practices. If the atmosphere in the kiln is normal and the space is adequate it not likely that there will be ill side effects to annealing longer than required. Not enough time on the other hand can cost you work.

If you want to go with manufacturers numbers you are limiting yourself to only using Vetro with Vetro, Cim with Cim, ect. Once you begin using more than one glass manufacturer you need to be finding a happy medium between the companies suggestions. I could never be happy with one color palate. I use a schedule that can handle some varied coe's and viscosities.

Glass is not one COE or viscosity, no matter what any manufacturer says (note the +/- 1.5 in the above chart). The colors are created to be as close as possible to the magic number. If you use one color alone you can have an empirical scientific formula to stand on, otherwise you need to use some form of generalization.

There is also a comprimise between proper annealing and acheving certain color combinations. Striking colors may require longer or shorter periods of annealing to get the desired effect. The science of annealing and the art of color can sometimes be at odds. It really depends on your end goal.

Simply stated, it is not likely to reach an exacting answer on the one perfect anneal schedule.

[Lyssa]

Turns out the "ick" really has nothing to do with the Devardi Mini Bead Annealer. I had a friend (CheriB) anneal a bunch of my beads for me and all the "problem colors" that were previously coming out "icky" in the Annealer came out "icky" in Cheryl's kiln.

*groan*

[Lisi]

Originally Posted by Lyssa

Turns out the "ick" really has nothing to do with the Devardi Mini Bead Annealer. I had a friend (CheriB) anneal a bunch of my beads for me and all the "problem colors" that were previously coming out "icky" in the Annealer came out "icky" in Cheryl's kiln.

*groan*

Oh no! Are you on a HH and using propane and not MAPP or bulk propylene?? Please tell me that's it because if it is, then your problem can be solved by changing to bulk propylene or another similar to MAPP fuel. Propane can ick up glass, that's the truth.

[Lyssa]

Nope, I'm on a Minor with Devilbiss 515 oxycon.

[Lisi]

Originally Posted by Lyssa

Nope, I'm on a Minor with Devilbiss 515 oxycon.

Okay, now...this is weird! Now I'm wondering about your flame chemistry. Do your candles have yellow or blue tips?

[Damselfly]

If they looked fine after being torched, but got devit after being batch annealed, it would have to have something to do with the annealing, wouldn't it? And since that explanation of annealing said it had to do with the glass crystallizing, I'm thinking that some glass is more prone to that when being reheated to less than molten state.

Whether it's due to how fast it ramps up, or just the temperature to which it ramps up, you may be out of luck trying to batch anneal those colors. I'm sorry you're going through this.

[Lyssa]

Yellow tips.

What would it mean if I had blue tips?

Originally Posted by Lisi

Okay, now...this is weird! Now I'm wondering about your flame chemistry. Do your candles have yellow or blue tips?

[jaci]

Yellow tips mean you are working in more of a reduction flame. Blue would be more neutral. This could be causing your problem. Your torch head may need some cleaning.

[Lyssa]

I always heard that you wanted blue candles with tiny yellow tips. Now I'm confused.

[squid]

You do want blue candles with tiny yellow tips.

[Lyssa]

Help! Contradicting advice!

[Lisi]

I always work in a slightly more oxygenating flame. So I dial out the yellow in the tips so I get just blue, but not to the point where the torch is hissing.

[jaci]

Yea. I find myself working in more of a slight hiss... And you may need to adjust your psi on your propane. I have mine set between 8-10. And work on a oxy con around 4.5-5Lon. Idk what the psi is. (and of course adjust at the torch there after)

[Lyssa]

I just discovered this thread which describes the exact problem I've been having, minus any mention of the ick showing up next to the bead holes.

[jaci]

Maybe you two should chat about the torch kiln etc and see what is common between you to narrow down a solution.

[Lyssa]

Yup, sent her a PM.