[Bette]

Hi, new potter here. I have been firing test tiles along with pots with full loads in my kiln. If I were to fire just test tiles - so the kiln would be relatively empty - would results closely replicate what I would see with a full kiln? I use a Skutt electric kiln with controller and Envirovent.

I also want to say how much I appreciate this forum and all the advice I am finding here. Very practical and inspiring, so thank you!

[Chris Campbell]

Good question ... sounds like it should be easy to answer, but it's hard to say.
My best guess is that your almost empty firing would be quicker and I suspect cooler due to fact that Cone temp is a combo of time and temp.

[yedrow]

The impressions I have from my reading is that the heat load can effect the glaze. A smaller kiln has a smaller heat load. The smaller the heat load the quicker the cooling, and the rate of cooling effects the growth of crystals in the glaze, especially more matte glazes and 'floating' glazes. I would guess that if you down-fire your kiln (bump it with heat to slow the cooling), you will get the same effect as a fully loaded kiln cooled at the same rate.

Joel.

[Lucille Oka]

When I used to fire low cone 05 bisque and cone 05 glaze fire, testing was an easy thing to do. All ware to be bisqued including the test tiles were put together and all glazed test were all put together
But since you seem to want to isolate your glaze tests why not put all of your tests on one shelf. If you use half shelves keep a space between them so air can move freely through the kiln.

[neilestrick]

To get accurate results, you'll need to fire down as well as up. The trick will be figuring out what rate to fire down that approximates the cooling cycle in your typical firings. The other option is to always fire down in your regular firings, too.

[SmartsyArtsy]

I've wondered about this also but intuitively avoided firing such light loads. It does draw out developing and testing different recipes. Even though my kiln is relatively small, I have thought about getting a test kiln. Would a small test kiln produce more accurate results ( compare to full load of larger kiln)?

[yedrow]

CSC, on 23 October 2012 - 11:24 PM, said:

I've wondered about this also but intuitively avoided firing such light loads. It does draw out developing and testing different recipes. Even though my kiln is relatively small, I have thought about getting a test kiln. Would a small test kiln produce more accurate results ( compare to full load of larger kiln)?

I don't think small kilns fire as evenly as larger kilns since their ratio of wall surface to the heated mass is larger, making them loose heat faster.

Joel.

[Chris Campbell]

I agree. I have a small test kiln that I use for small batches and tests. It gives you approximate results but it is very hard to get it to mimic the firing profile of my large kilns. Close enough for some things but not accurate for glaze tests if you want predictable results.

[neilestrick]

The only way to get a small test kiln to give results the same as a big kiln is to fire up and down on the same schedule.

[Kohaku]

yedrow, on 23 October 2012 - 09:03 PM, said:

CSC, on 23 October 2012 - 11:24 PM, said:

I've wondered about this also but intuitively avoided firing such light loads. It does draw out developing and testing different recipes. Even though my kiln is relatively small, I have thought about getting a test kiln. Would a small test kiln produce more accurate results ( compare to full load of larger kiln)?

I don't think small kilns fire as evenly as larger kilns since their ratio of wall surface to the heated mass is larger, making them loose heat faster.

Joel.

I've got a Paragon Firefly- it seems to do pretty well to cone 6. (I just have to back off the final ramp a bit).

Like a leaf on the wind...

[Bette]

Thanks to all for thoughtful and informative replies. I will continue to fire test tiles along with regular loads. Sounds more reliable and simpler.

[neilestrick]

I have two electric kilns, one 4 cubic feet in size, the other 20 cubic feet. The cooling times are different by about 18 hours, giving in very different results. I fire down in both kilns to about 1500F degrees and the results are nearly identical.

[yedrow]

er, lose...**groans

[Avaviel]

Wouldn't you fire your test glazes with the rest of the kiln? My reasoning is that if the test passes, you'll use it on your pots, which will be fired in big groups. The only way this would be a thing to do is if you had some pots that your fired by themselves.

I'm just thinking about this logically, so I may be wrong.

[Marcia Selsor]

I think you'd get a better result in a full kiln and fire as you intend to fire.
I have a small test kiln, 9 ht x 13 wide. I fire test tiles raised across triangular stills or on coils for full circulation of heat. I fire as many shelves as I can in there and use one on the top just under the shelf. I also put some thick fiber insulation on the outside top of the kiln. Itry to fire down but it is an old manual kiln so that is a crap shoot. I also fire a cone hotter than the glaze would be in a full larger load.
These practices give me pretty good results.

marcia