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Finding the sweet spot?


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#1 Nelly

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Posted 03 November 2012 - 12:57 AM

Dear All,

As I plan a weekend of massive glaze firing from work I did in the summer, I am wondering if there are any hard and fast rules for finding the right spots in an electric kiln for optimum results.

For example, in my old studio in Toronto, the middle of the kiln was always the hottest. Thus, my matt black glaze always looked great when it came off this shelf. I am finding my matt black doesn't look right anywhere in the kiln?? ;)

In my old studio, the saturated iron and Rosie's red always looked good on the bottom shelf. Here, in my new kiln, they lack the character I was accustomed to seeing. They do not melt into the creases or some the same transitional coloration as well. Thus, while shiny, they do not have the same finish I am used to in the past despite the exact same glaze recipe.

Can we say that, anything with iron in the glaze needs more heat or is attracted to a hotter spot in the kiln??

Is finding the best spot a matter of trial and error?? I mean, technically in these computerized kilns everything should be the same throughout--right?? Or am I wrong??

And I still work by the premise that hot air rises to the top so this should be the hottest spot??

Anyway, I could just be grumbling as I get to know my kiln but it is hard to ascertain. I am using predominantly glazes that I had mixed from recipes I know. These are not commercial products so it is baffling me a bit.

Nelly

#2 atanzey

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Posted 03 November 2012 - 06:27 AM

Have you done your past firings with cone packs on all the shelves? You may need to adjust the computer a bit. What you're describing sound like maybe, just maybe your kiln has underfired the pieces a bit from what you're used to. My L&L has offsets for the various cone values, and using them, you can adjust the amount of heatwork.

Or, you could add a very short hold at the end, and see if that helps. I did that last firing - I think only 10 minutes - and everything came out just a touch overfired (but nothing ruined. So that was the wrong approach..... Live and learn!

Alice

#3 neilestrick

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Posted 03 November 2012 - 09:20 AM

Kilns that do not have zone control will almost always have hot and cold spots. You'll need to experiment with how to load the kiln to even out temperature variations. Generally, load loose at the bottom, tight in the middle, medium tight at the top.

The top is not always the hottest, because there is heat loss out the lid. The middle is generally the hottest.
Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#4 Nelly

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Posted 03 November 2012 - 09:24 AM

Dear Alice,

I will likely contact my kiln support people to ask about this issue?? I am currently awaiting the results of my cone 7 firing. We will see??

Last night, I simply moved the numbers up on the display panel to what I thought was a 7 range.

I will know when I open it again later today if it does, as you say, need tweaking or if I am not doing something correctly (i.e., putting in the right cone number when the digital screen comes up).

Oh how I loved the old kiln where I could play with the numbers and hold manually at the top temperature. Seems like everything I do on this machine I have to first think about how I did it before with the cones and Dawson and relearn it using the technology.

But, as I have been assured repeatedly, I will grow to love it.

And yes, there are cone packs on the shelves. I will know today, in particular, how it went at the bottom when I open the lid and unload.

Will keep you posted.

Thank you,

Nelly

#5 Ben

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Posted 04 November 2012 - 10:33 AM

Cones, cones, cones.
Thermometers read temperature. Ware in a kiln shows heat work which is the result of heat and time. Thermometers can't read time so they are useful only to a point.
As Alice suggested, cones will tell you what you need to know. You need a cone pack that covers your target cone and one above AND below. If you are firing to ^7 you need a 6-7-8 cone pack at the outer edge and the middle of the top, middle, and bottom. Make notes as you unload or take pics etc. You'll get different results with different loadings so note that too.

Alice, might I suggest you do your soak at a slihgtly lower temp. You'll have to experiment of course but it could even things out AND not overshoot your heat work goal (cone).

USE cones!
They are cheap and the info they provide just can't be arrived at any easier way.

good luck, good pots,
Ben

#6 Nelly

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Posted 04 November 2012 - 11:05 AM

Cones, cones, cones.
Thermometers read temperature. Ware in a kiln shows heat work which is the result of heat and time. Thermometers can't read time so they are useful only to a point.
As Alice suggested, cones will tell you what you need to know. You need a cone pack that covers your target cone and one above AND below. If you are firing to ^7 you need a 6-7-8 cone pack at the outer edge and the middle of the top, middle, and bottom. Make notes as you unload or take pics etc. You'll get different results with different loadings so note that too.

Alice, might I suggest you do your soak at a slihgtly lower temp. You'll have to experiment of course but it could even things out AND not overshoot your heat work goal (cone).

USE cones!
They are cheap and the info they provide just can't be arrived at any easier way.

good luck, good pots,
Ben



Dear All,

I am just going out to load my kiln. I will use cone packs throughout. I will get back to Ben.

I just know moving up from cone 6-7 really helped me. I may push it further today.

Thanks Ben.

Nelly




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