Annealing Temps

Mira · Post by **Mira** » Tue Jan 20, 2004 10:25 pm

Okay, so I have a Hotstart Skutt Kiln. Now that I'm working with much thicker pieces, I need to add annealing time to my program. Skutt says no-can-do, the computer that comes with the kiln is set up for system 96.
I say thats fine, I use system 96, but that still doesn't help me when I want to fuse thick pieces or do box casting.

So, of course, I try to out fox the controller. I figured I'd run my regular program for process temp and time, then shut down that program at the end of the process time and re-program for a couple hours at 980. Clever, huh? Trick is, the lowest temp my controller will let me process at is 1000.

So, here's the question: (Finally, you're saying) . . . .
Will glass anneal at 1000, or is this a waste of time altogether?

Thanks!
Mira

Amy Schleif-Mohr · Post by **Amy Schleif-Mohr** » Tue Jan 20, 2004 10:37 pm

Mira,

You need to understand what annealing is. It is the slow decent of temp. through a given set of temp. It's not just one temp. or sitting at one temp. for a given amount of time. I don't use S96 so I couldn't tell you what the range is but hopfully someone else with experience will.

Good luck,
Amy

Mira · Post by **Mira** » Tue Jan 20, 2004 11:08 pm

Hi Amy,

Thanks for the tip. After a little more research on the Spectrum site, I found this:

"Different colors have different â€œidealâ€

Judy Schnabel · Post by **Judy Schnabel** » Tue Jan 20, 2004 11:13 pm

Mira,

Can't help you with programming your controlller, but you hit the nail on the head with annealing temps for System 96.

I hold at 955 then take the kiln down 150 dph to 700.

Judy

Amy Schleif-Mohr · Post by **Amy Schleif-Mohr** » Tue Jan 20, 2004 11:24 pm

So Mira,

Correct me if I don't understand... You can't program your controller to go below 1000F, be it going slowly or soaking.

How thick are you working? 1/2"? 1"? 2"?

I can't remember if you indicated that your kiln is fiber or brick.

Amy

Mira · Post by **Mira** » Tue Jan 20, 2004 11:31 pm

Hi, Amy,

Yep, you got it right. It's a brick kiln, meant for glass and all. Skutt came up with this kiln and it's meant for newbies. Basically, you pick if you want to go fast, medium or slow. Then you pick if you want to slump, tack or fuse. You can then muck with the process temp and hold times. You can add time while you are processing and you can skip to the next segment. It's all well and good, but you can't add time to the annealing portion of the program - you have to stick with Skutt's pre-programs on that part.

So, needless to say, it's a great way to jump in and get your feet wet, but I have to admit, I'm a bit dissapointed. I want to do some box casting as set out in Glass Craftsman, but it doesn't look like my kiln will be able to anneal anything beyond 3/8 " properly.

Unless, of course, I can out-fox the darn thing. And my only thought on that was to try to run two programs back to back: the first one dealing with the process times, the second one dealing with annealing. When I lower the temp as far as it goes, it will not go lower than 1000.

Why would Skutt do that? Skutt, if you're out there . . . please chime in.

Thanks again to anyone who has an idea!

Mira

Amy Schleif-Mohr · Post by **Amy Schleif-Mohr** » Tue Jan 20, 2004 11:43 pm

Well Mira, I had an idea but I don't think it's going to work for a box casting. The casting will be way too thick. The ones I've seen are at least an inch and a half thick and that takes a couple of days to fire, minimum.

Sorry you are kinda stuck.

Hope you can figure it out.
Amy

Mira · Post by **Mira** » Tue Jan 20, 2004 11:56 pm

Amy, I'd still love to hear your idea - right now I can only go to 3/8" thick, so if I can increase that at all, that'd be great.

Thanks again,
Mira

Lynn g · Post by **Lynn g** » Wed Jan 21, 2004 12:20 am

Mira, I'd hate to think you've outgrown your kiln but I suspect that may be the case. According to Phil Teefy (welo-known and experienced fusing instructor and kiln builder), Bullseye glass 6-18" in diameter and 3/8" thick needs to cool at 60 degrees/hour thorough the annealing zone; 7/16" thick should cool at 30/hour and 1/2" thick should anneal at 12 degrees per hour. A fused block 8x8x1" thick needs to go from 1200 degrees to 950 at 300 degrees per hour and hold for 3 hours, then at 16 degrees per hour to 760 (this takes 12 hours). Then cover the glass with K-Wool at 760 and cool at 60 degrees per hour to room temperature. I would expect the time frame for System 96 glass would be pretty similar.

My point is, for thick work you're looking at a considerable amount of time for annealing, as well as the need for accuracy in temperature to avoid annealing stress, which will cause your piece to break at some point in time. I can't imagine wanting to fool around with trying to out-fox the controller for that length of time, especially when the piece may bery well break anyway. (I finally broke down and spent the bucks for a Rampmaster for my Evenheat because I was tired of using the infinite switch, setting the timer and running out to the kiln constantly, and still not being able to control what was happening!)

Suggestion...if you just got the kiln, why don't you try contacting Skutt, explain your problem, and see if they might be willing to take the kiln back and give you at least a partial credit towards a kiln that will be able to do what you need it to? Failing that, look for a buyer with no ambitions to go thick!

Good luck!

Lynn

Lynn g · Post by **Lynn g** » Wed Jan 21, 2004 12:25 am

Mira, after I sent my reply, I happened to notice you are in Lodi. You are vertainly close enough to get in touch with Phil Teefy at Rainbow Glass in Sacramento. He has which cover block fusing which you might find very helpful. His websire is http://www.glassglow.com

Lynn

Mira · Post by **Mira** » Wed Jan 21, 2004 12:35 am

Double farts.

Thanks for all the help, though. I had always planned on holding on to this kiln for smaller things and push for a bigger kiln when the time comes. That way, I would have two kilns with different capabilities. Looks like the time is coming sooner than later.

Marty · Post by **Marty** » Wed Jan 21, 2004 9:08 am

12 dph for 1/2" thick glass is ridiculously conservative. And it doesn't make sense- the 8x8x1 block takes a 16dph ramp and the 1/2" takes 12?
And why would you want to open a kiln at 760 on the way down to throw a blanket on your glass when the same effect can be achieved by powering down slowly without the risk of thermal shock?

Tony Serviente · Post by **Tony Serviente** » Wed Jan 21, 2004 9:37 am

I am as puzzled as Marty. Either I have pleased the gods and benefitted by their blessing of my glass, or a considerably faster schedule works.
As to the controller, can you put a switch in to bypass it. It'd be like going from automatic to manual trans in a car. Might be tedious, but then you could get it to do what you want by either turning it off and on, or better yet, put an infinite switch in the line.

Tony Smith · Post by **Tony Smith** » Wed Jan 21, 2004 9:48 am

Lynn g wrote:Mira, I'd hate to think you've outgrown your kiln but I suspect that may be the case. According to Phil Teefy (welo-known and experienced fusing instructor and kiln builder), Bullseye glass 6-18" in diameter and 3/8" thick needs to cool at 60 degrees/hour thorough the annealing zone; 7/16" thick should cool at 30/hour and 1/2" thick should anneal at 12 degrees per hour. A fused block 8x8x1" thick needs to go from 1200 degrees to 950 at 300 degrees per hour and hold for 3 hours, then at 16 degrees per hour to 760 (this takes 12 hours). Then cover the glass with K-Wool at 760 and cool at 60 degrees per hour to room temperature. I would expect the time frame for System 96 glass would be pretty similar.

My point is, for thick work you're looking at a considerable amount of time for annealing, as well as the need for accuracy in temperature to avoid annealing stress, which will cause your piece to break at some point in time.

Lynn

12Â° per hour is incredibly conservative. Take a look at Bullseye's chart for annealing thick glass. Their recommendation is 120Â° per hour for Â½ inch thick glass. Being extra conservative from there would be 75Â° per hour. This rate can be accelerated below the low end of the annealing range (below 750Â° to be conservative)... there's no need to maintain this rate to room temperature. http://www.bullseyeconnection.com/pdfs/ ... _thick.pdf

Tony

Mira · Post by **Mira** » Wed Jan 21, 2004 12:08 pm

Tony,

What's an infinite switch? Would that mean I could just Bypass the controller? That would work for now!

Mira

charlie · Post by **charlie** » Wed Jan 21, 2004 12:20 pm

you should ask skutt if they'll sell you, or trade you, a different controller circuit board. the case and all the rest of the controller is the same. you want the standard version that comes on, for instance, the gm1414 or gm1014.

what if you outfoxed the controller by setting the 1000 degree point, then decreased at, say 50 dph for 3/8. it's ok to go slowly above the real anneal point too, it just takes you a bit more time.

Tony Serviente · Post by **Tony Serviente** » Wed Jan 21, 2004 12:33 pm

Mira-Most switches are either on or off, with nothing in between. An infinite switch has either a few in betweens, like high, medium and low, or a continuous range, like a rheostat. They do this in various ways, but it means you have "infinite" control. A switch for an electric range would probably do it for your kiln, and your local appliance store will either have a new one in their repair dept. or may have an old one to give you. Thing to be careful of is that the amperage rating is as high, or higher than your kilns. I would also strongly suggest that you do this with the help of someone who knows their wiring. It is really easy, but anytime you start working with line voltages the risk of injury, death, or property damage is there. What may be easier, and is certainly cheap enough is this cool gadget http://www.ekmillerco.com/detail.aspx?ID=20. You cold bypass your controller, and plug the kiln into it. Good luck.

Mira · Post by **Mira** » Wed Jan 21, 2004 1:32 pm

Thanks Guys. Luckily for me, my hubby is an electrical engineer. I'll see what Skutt is willing to do for me. If nothing, then I'll see about that Infinite Switch.

Thanks again,
Mira

Tony Smith · Post by **Tony Smith** » Wed Jan 21, 2004 2:09 pm

Another option would be to contact Bartlett and see if you can buy a new chip for your controller. They have the same controller available with four fully programmable, 8-step programs.

Talk to Rob Bartlett. (319)372-8366 http://www.bartinst.com

Tony

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