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Manual Kiln Question

By November 9, 2010

Q: I recently purchased an old JenKen kiln to fire my hand built pottery.... This 40+ year old kiln has 2 knobs, each with a low, medium and high setting. How
do I know how long I leave the kiln on each of the 3 settings for a high fire
greenware to bisque firing, and then a glaze firing? I'm just not sure of the
timing and do not want to over or under fire my pieces. I'm so excited to do this
yet so nervous, and the nervous side is winning....

A: Hey, don't think you're alone in this! I think all of us have at least some anxiety when firing a "new" kiln for the first time, no matter how long you've been doing it!

For a bisque firing, load the kiln sitter ( see How to Use a Kiln Sitter) with a cone or rod for the cone you want to fire to, e.g. a ^04 cone or rod for an earthenware bisque.

If by chance your kiln doesn't have a kiln sitter, load a cone pack and place it where you'll be able to see it from a peek hole when you stack the kiln.

Again, we're talking a bisque load --- once the load is stacked, close the kiln. Put the bottom-most switch to low. Leave at that setting for one to two hours (depending on humidity -- more moisture in the air, give more time).

Turn the top switch to low, and heat for four hours with both switches on low.

Turn the switches to medium and heat two hours.

Turn the switches to high, and fire until temp is reached. The kiln sitter should automatically shut the kiln down, but if yours doesn't have a sitter, you'll need to keep an eye on the cone pack, especially once the kiln is incandescent inside.

Glaze firings are a bit simpler. The one problem you may encounter is reaching temp if you are firing above earthenware ranges. Many older used kilns can have trouble reaching ^5-^6. They just don't have enough insulation to be really efficient.


If your kiln does have trouble reaching temp, you may need to replace your kiln elements. You might also consider adding more insulation by wrapping a refractory blanket (e.g. Kaowool) around the outside of the kiln, being sure not to cover the switch boxes, kiln sitter, and peep holes.

For a glaze firing, after loading the kiln turn both switches to low for two hours.

Turn the switches to medium for two hours.

Turn the switches to high until the kiln reaches temp.

Comments

November 9, 2010 at 5:06 pm
(1) Robyn says:

These instructions will be so helpful. After staring at this kiln for so long, I will now, FINALLY, be able to fire all of my pieces that have been sitting and drying for months.
I’m so grateful for your advice, your website and your knowledge.

November 14, 2010 at 6:37 pm
(2) Steve Mconald says:

Robyn,
That’s so exciting that you’ve found a way to fire your work. I’ve worked with several very old kilns in the past as well and have always been thankful just to have one.

One other thought when you’re getting to know your kiln is don’t fire a whole load in it until you’ve got the process down. It’s no big deal if you ruin 5 pots while practicing with the kiln, but it can be heartbreaking to ruin a whole load of pots that you’ve been working on for months.

Be patient on those first few firings and before you know it you’ll be packing it full of pots and firing with confidence.
Steve

November 18, 2010 at 3:25 pm
(3) Marina says:

I have one very old kiln with kiln sitter. I call my kiln “old reliable horsey” :) So great it fires my bisque and glazed pottery.
I was lucky to get it from retired potter with instruction. Schedule is almost the same like Beth explained, only on low I hold it for an hour and lid is crack opened (my kiln has a special holder) on low and on medium, I close it only when switch on high.
Good luck and I hope your “old horsey” will work for many years.
Marina

November 19, 2010 at 10:27 am
(4) Sherryl says:

I also have a JenKen kiln, over 40 years old, but in good shape. This one has no knobs to turn, only a kilnsitter contol. I was able to call the company here in FL that makes them and got the directions for firing. It also has two lids and two plugs. Like I said, this is old! It uses two separate currents, and the lids help to get it from low to med. to high. Though it can fire to cone 8, it was suggested to treat it gently, like an antique. I use it for low fire or even gold or decal firing.

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