Skutt Glaze Tech Kiln

[Smokey2]

I'm considering purchasing a Skutt Glaze Tech Test Kiln (GT) to go with my L&L E28 with a Genesis controller.

I mix my own glazes and have my firing schedules down pretty good with a slow cool down to 1400°.

I would like to program the GT to fire glazes as close as possible to the L&L. The one thing I noticed is that the GT thermocouple isn't protected like the L&L's. What kind of difficulty might I be facing to acquire some consistency between the two kilns?

[neilestrick]

As long as you do the same firing profile you shouldn't have any problems with consistency. The slow cool is key, as the small kiln will want to cool much faster. As for the thermocouple, the problem with an exposed thermocouple is that they tend to shed, dropping little bits into the kiln. In a large kiln, that's only going to affect a small area. In small kiln, it can shed on a much larger percentage of the kiln. I've got a baby kiln where 1/3 to 1/2 of the floor is covered with TC shedding. Because the kiln is so short, the TC is pretty close to the floor, so the shed doesn't fall all over everything as badly as in a taller kiln. So you can either order that kiln and not worry about it, order that kiln and put a protection tube on it, or order a kiln from L&L that already has a protection tube. If you're set on that kiln, just add a protection tube. You'll just need to put in a TC offset to compensate for the insulating factor of the tube.

[Smokey2]

Good Info

My L&L has an offset of 18° and I glaze fire to 2195°.

If I do not add a protection tube to the  GT should I program the kiln to fire to 2195° or 2213°?

 

[neilestrick]

1 hour ago, Smokey2 said:

Good Info

My L&L has an offset of 18° and I glaze fire to 2195°.

If I do not add a protection tube to the  GT should I program the kiln to fire to 2195° or 2213°?

 

2195

[Smokey2]

That's distressing, that means my understanding of TC offset has been wrong for many years

[neilestrick]

25 minutes ago, Smokey2 said:

That's distressing, that means my understanding of TC offset has been wrong for many years

That offset is what makes it accurate. If you didn't have the offset, it would over-fire by 18 degrees.

If you didn't have the offset, if the inside of the kiln is 1000F, then inside the TC tube it's 982F, 18 degrees cooler, and that's what the controller would read. So if you fired until the TC read 1000F, then it would actually be 1018F in the kiln. We bump up the reading of the controller 18 degrees so that when the kiln is at 1000F, that's what the TC is reading, too.

[Babs]

Is the 18deg cited a pplicable to all t.c.  in protective sheaths?  

 

[Bill Kielb]

31 minutes ago, Babs said:

Is the 18deg cited a pplicable to all t.c.  in protective sheaths?  

 

L&L worked that out for their combination. Since kilns are similar, I would guess that is fairly universal for Similar pottery kiln application.
My personal experience  in different environments: incinerators, rotary kilns, stack temp .......... we would calibrate for the environment.  The calibration  would differ by size, length, wall thickness of the protection as well as thermocouple type and refractory thermal conductivity.

For the alpine gas kilns  in the studio we measured the the difference as less than ten degrees for their standard protection tube and thermocouple combination. Since those kilns are all about watching cones we just never bothered to offset them.

[liambesaw]

Your TC offset has only been wrong for several years if you havent been using witness cones and have blindly been following what your thermocouple says

[Bill Kielb]

8 hours ago, Smokey2 said:

Good Info

My L&L has an offset of 18° and I glaze fire to 2195°.

If I do not add a protection tube to the  GT should I program the kiln to fire to 2195° or 2213°?

 

Like @liambesaw mentioned above, do you confirm with cones?  To get an automatic controller to stop at the right cone it takes some final segment programming to fire at a rate and ending temp as published in the Orton chart.

If you are relying on an automatic cone fire program, the programmers took care of this for you. So the good question would be what cone have you been verifying to. Picking an ending temperature without an ending rate in the last 200 degrees of the firing is unpredictable with respect to what cone did it fire to.

Gotta have witness cones to know.

[neilestrick]

1 hour ago, Babs said:

Is the 18deg cited a pplicable to all t.c.  in protective sheaths?  

 

I think it depends on the thermocouple, tube makeup and thickness, and how far it extends into the kiln. L&L has changed their offset at least once in the last 20 years.

[Mark C.]

My offset changes daily

[Babs]

1 hour ago, Mark C. said:

My offset changes daily

How are you measuring the offset required prior to firing?

Gut feeling?

How the fish are biting?

I've got cones in and watch during last hour.

Easier as I haven't adjusted controller and spent a life watching cones and colour and listening to noise of gas.....

Also never trust a thingie to shut down for me.

Murphy sits on my shoulder I figure

[Babs]

Oh so my setting end temp lower than cone in kiln is offsetting????

Doing that from logs kept and cone down temps in earlier  firings!

:-))

[Mark C.]

some days I offset where I sit on the couch others its offset by lack of enough coffee

[Smokey2]

FWIW,

Years back when I first started I installed a thermocouple  on my sitter kiln. Days later I noticed that when I took a reading  that the temperature inside the kiln  had a reading that was higher than the room temperature, even when it has been off for over a week. I decided at that time not to really concern myself with the shown temperature except to use it as a guide for each firing. 

When I acquired a new kiln with a controller and I turned it on for the first time I noticed the same thing, a higher temp in the kiln than the room temp, I figured it was the TC offset.  I adjusted my firings to what worked the best with my glazes using the readings as a guide and not to be relied on as the actual internal temps.

My belief has always been that consistency was upmost important and the temp shown on the screen was only a guide.

I've kept detailed records of every firing that I have completed which includes:

• Temps readings at 30 minute intervals on the sitter kiln
• Dial adjustments for slowing down parts of the firing on the sitter kiln to make it easier to duplicate future firings
• Witness cones in every firing
• A photo of the fired cones
• On the L&L I placed cones on every shelf until I had my firings dialed in
• Now I place just one set of cones in a different area of the kiln for each firing
• Detailed notes of each firing which includes success, failures and what to improve on.

The readings and photo is stored in a spreadsheet for easy reference. The Genesis controller makes this easy to do

 

[neilestrick]

At room temp when everything is cooled down, the TC offset will make the controller read hotter than room temp. However once the kiln is firing, that offset compensates for the tube keeping the TC cooler and lagging behind the actual kiln temp.

I never use cones in my digital kilns. I figure that if there's a problem in the firing I'll see it in my glazes, and having cones in the kiln won't prevent it from happening. For me a big part of the reason for having digital kilns is so that I don't have to mess with cones any more. Plus with the number of firings I do at my studio it could cost me up to $350 a year on cones.

[Smokey2]

On 5/2/2020 at 12:51 PM, neilestrick said:

I never use cones in my digital kilns. I figure that if there's a problem in the firing I'll see it in my glazes, and having cones in the kiln won't prevent it from happening. For me a big part of the reason for having digital kilns is so that I don't have to mess with cones any more. Plus with the number of firings I do at my studio it could cost me up to $350 a year on cones.

Impressive, $350 on cones would be about 480 firings in a year. Last year I completed about 40, I was hoping more for this year but pandemics happens when you least expect it.

I find I can spot problems with using cones before it shows up in the next glaze firing

======

Anyone here own a GlazeTech? If so, can I PM you and ask a few questions?

[neilestrick]

I actually did the math wrong there. Large cones cost about $13.50 for a box of 50, or 27 cents each. Each firing needs 3 cones- 5,6,7 for a cone 6 firing. I'd put 3 cone packs in my medium kiln- bottom, middle, and top. So 9 cones per firing, 100 firings a year, or 900 cones at 27 cents each, for a total of $243. In my big kiln I'd probably put 6 cone packs in if I really wanted it to be worth using them, since it can have horizontal temperature differences as well as vertical. So 18 cones per firing, 40 firings per year, for a total of $194. My baby kiln would need one cone pack per firing, 60 firings per year, for $49. That puts the total at $486 per year. I've had these kilns since 2008, so in 12 years of not using cones, I've saved almost $6000 dollars. Probably more, since I used to do a lot more kids classes and had to fire the medium kiln several times a week during summer workshops.

I'm not saying people shouldn't use cones. For a lot of people they're the best way to keep track of firings, I've just never found them to be necessary for me. If you're really tuned into your glazes, they'll serve the same function as the cones.

[Smokey2]

I use large cones, not the self supporting ones and use just one large cone pack set per firing in my L&L E-28. It costs me 75¢ per firing so based on 40 firing it cost me $30 last year. Cheap insurance since it saved one firing last year.

I bisque to 1969° and my 05 cone was barely bent. In this firing I had a clay that has pinhole problems with certain glazes. If I had glazed these pots it would have been a total loss.

Digital controllers are great but they are not fool proof or perfect. "Trust But Verify"

So much for asking about a Skutt GlazeTech

[neilestrick]

That's not a very common kiln. But based on Skutt's history, it should be a good kiln. The only thing I wish they had done differently is the controller. The 3 button controllers work just fine, but they're not nearly as user friendly as the full size controllers. As a test kiln, it should have a controller that's easy to use for custom programs, like the new touchscreen. Their web site doesn't show that as a factory upgrade, but it may be something you can add yourself. They make an upgrade kit for their full size controller, and it may work as a 3-Button upgrade with minor modifications.

[Smokey2]

5 minutes ago, neilestrick said:

The only thing I wish they had done differently is the controller.

Agreed

[neilestrick]

1 minute ago, Smokey2 said:

Agreed

Since you're going to be hooking up a 240 volt circuit anyway, I'd take a look at some of the other test kilns on the market that have better controllers. Paragon, L&L, and Olympic all make test kilns that have similar volt/amp requirements, but with a full size controller.

[Stephen]

ah crap, u guys have now cost me a couple of hours. Never heard of offset and now I have to go and surf on it and that always leads to more surfing and eventually I may even end up in YouTube hell.

Thanks a lot.

[neilestrick]

22 minutes ago, Stephen said:

ah crap, u guys have now cost me a couple of hours. Never heard of offset and now I have to go and surf on it and that always leads to more surfing and eventually I may even end up in YouTube hell.

Thanks a lot.

Glad we could be of service! Watch out for cat videos.