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Help Firing Electric Kiln Without Pyrometer

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Hello all. I am new to this forum and pottery.  

I recently purchased my first new-used kiln. A Cress B23-H. I think I finally have it set up and am ready to fire. However, I do not have a pyrometer yet and the kiln-sitter does not have a timer. 

I have been doing extensive reading about kilns and firing. All schedules and firing guides and info speak in terms of degrees/hour. I know I need to get a pyrometer but I’ve spent lots of money getting the critical stuff set up so I’m out of funds at the moment. But I am anxious to get firing!

So my question is: does anyone have any tips on firing without a pyrometer? And my kiln sitter does not have a timer. I ,of course, use cones and I can fire and see how long it takes for the cone to bend, but that doesn’t quite giving me a rate of heating up when there are multiple phases before the target cone bends and the temp increase is reached. 

I would appreciate any of your expertise’s!

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I have been firing electric kilns for over 40 years and have never worried about the exact rate of climbing of temperature.  A lot depends on how full your kiln is and what type of work you do.   I hand build,  sometimes I candle it over night or put it on low for 3 or 4 hours,  then I turn it up to medium in a couple of hours  high.  It always takes me a good nine hours to fire a glaze firing,  I fire to Cone 5/6.   I   I like working with stable glazes that I can just fire  and not have to mess with.    Tony Hansen a creative glaze designer is developing these type of glazes.    I have a Skutt pyrometer set up that I can use to down fire and hold with but I rather work with a stable glaze.   Denice

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I have a Cress B-24-H. This is the firing schedule for glaze ware that has been bisque fired...

all    low    2 hours

all    med    2 hours

all    high    finish

Be sure to get and use bar cones instead of the normal 3 sided cones in the claw of the kiln sitter. I do not have a pyrometer.

 

 

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No timer needed. The timer has nothing to do with the rate of climb or how long the firing takes. It is simply a countdown, and when it reaches zero it turns off the kiln, regardless of whether or not the firing has reached the desired peak temperature. The idea is that you set the timer to about half an hour longer than you expect the firing to take. It's a backup safety device, there to shut off the kiln in case something goes wrong with the cone system.

No pyrometer needed, either. You can't really control the rate of climb very much in a manual kiln, and it's not really necessary.

For bisque firing work that is dry, do an hour on low, an hour on medium, and an then high until it shuts off. You can go slower if you have thick work. If things aren't totally dry, put the bottom switch on low for a few hours before progressing with the firing.

For glaze work that is dry, an hour each on low and medium will work fine, too. You could even go faster than that if you want to, and your work is relatively thin and even.

Bars can be difficult to find sometimes. The 3 sided cones will work fine, just aim the little number towards the inside of the kiln.

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When firing a kiln, the concepts of temperature and rate of increase are a conundrum in that it is possible to both place too much importance and too little importance on the precision of either number.  Because electronic controllers are just dumb specialized computers, one must tell it what to do and it will attempt to do exactly that, hence all the mumbojumbo about rates and temperatures. However, the reality of the ceramic process is that there is considerable leeway around it, most of the time. There are a few times during the heating process that the rate of increase should be slowed down to prevent physical damage to the developing ceramic, specifically at around 900F and again at around 1150F.  The firing schedule suggested above by dhPotter, starting with switches on low heat, then turning the switches up over a period of hours will accomplish this without needing to worry about the exact rates and temperatures. Low and medium will not provide enough heat to exceed the limits. The final stage of heating is a different kettle of fish. This is where the witness cones are essential. The cones measure heatwork, not temperature. Heatwork is the penetration of the heat into the ceramic body, and that occurs over time. It you increase the temperature very fast during the last 2 hours of the firing, it will still take time for the heat to penetrate to the center of the ceramic, which means the actual temperature of the air in the kiln will be higher when the designated cone softens and bends. If you increase the temperature during the last 2 hours very slowly, the heat will be penetrating into the center of the ceramic at almost the same rate, and the cone will soften and bend at a lower actual temperature. When you have a manual kiln, you turn it to high, it does what it can to heat the contents of the kiln (the manufacturers design their kilns to have enough heating power to do what is needed), and the cone bends when it is done. That's when you turn it off. If the load is light and it heats faster than usual, it will heat to a higher temperature and the cone will bend when it is done. If the load is heavy and it heats slower than usual, the cone will bend at a lower temperature and then it is done.

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dick, excellent description of how the kiln works.

since the questioner is a real beginner, maybe you can edit that sentence near the end that says "That's when YOU turn it off."  maybe indicate that the bent cone causes the electricity to stop at that point, no human needed.    

can't be too careful with new folks.

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This is so helpful to me! I am also new to this forum and have recently purchased an old Cress B-23-H.

I am currently running my second Glaze Firing, and I am wondering if there is any reason to turn the dials toward high fire? For my first Glaze Firing, I had the dials to Low for one hour (DIY downdraft vent that I installed on), Medium for 2 hours, and High for 4.5 hours and I was feeling it was taking longer than expected so I turned the dials to High Fire and two hours later it shut off. (And I used a cone 6 Junior cone in the kiln sitter, but the Witness comes showed a firing to Cone 5.)

My question is should I just leave it at high and wait it out this time? I turned it to high fire last time in thinking that maybe the kiln wasn’t getting as hot as it should. 

As for not getting up to Cone 6, I tried using the thicker end of the cone. If that doesn’t work, I’m planning to use a Cone 7 Jr cone. Or I was told to try turning the kiln back to high for one hour after it shuts off.

Thanks to anyone who has thoughts! It’s good to know others have this same old kiln out there :)

Edited by RAstudio

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2 hours ago, RAstudio said:

 

As for not getting up to Cone 6, I tried using the thicker end of the cone. If that doesn’t work, I’m planning to use a Cone 7 Jr cone. Or I was told to try turning the kiln back to high for one hour after it shuts off.

Thanks to anyone who has thoughts! It’s good to know others have this same old kiln out there :)

From experience I can tell you that it does not matter much if you try to use a thicker or thinner part of the cone because the cone will soften and slump based upon the temp, not on where the little rod touches it.   And once the electricity is turned off by the kiln sitter, the dial position does nothing because no electricity is getting to the switch.  In other posts many folks have discussed hot and cool spots in a kiln.  You may want to place several witness cones to see if your firing is uniform throughout.  It could be that your witness cone was in a cool spot and other parts (particularly the middle where the cone sitter is located) was hotter.  Early on I bought a pyrometer that I  can stick in through the inspection holes.  I made a plug that holds the probe in the proper orientation and I have never regretted the expense.  being able to watch the temps makes it so nice .  And amazingly enough, DH Potter's schedule is nigh on to perfect for the heat ramp up on my kiln.

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17 minutes ago, Viking Potter said:

From experience I can tell you that it does not matter much if you try to use a thicker or thinner part of the cone because the cone will soften and slump based upon the temp, not on where the little rod touches it.   And once the electricity is turned off by the kiln sitter, the dial position does nothing because no electricity is getting to the switch.  In other posts many folks have discussed hot and cool spots in a kiln.  You may want to place several witness cones to see if your firing is uniform throughout.  It could be that your witness cone was in a cool spot and other parts (particularly the middle where the cone sitter is located) was hotter.  Early on I bought a pyrometer that I  can stick in through the inspection holes.  I made a plug that holds the probe in the proper orientation and I have never regretted the expense.  being able to watch the temps makes it so nice .  And amazingly enough, DH Potter's schedule is nigh on to perfect for the heat ramp up on my kiln.

Thank you! This is helpful info. Where can Ifind DH Potter’s schedule?

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I had a Cress (used) about 45 years ago. I agree with dhpotter, just a simple, 2 hours on low, (with lid cracked open til steam stops..check with a mirror or mason jar, by watching if they fog up) shut the lid after 2 hours or if you still have steam, shut after the first hour n medium,.

2 hours on medium turn to high until finish. Check after 8 hours after beginning.

Marcia

 

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