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lukeseall

Kiln not reaching temperature

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I have just bought a second hand top loading electric kiln (Potterycrafts P5976 Electric Toploader).  I completed a bisque firing to 1000 deg successfully.  I have been glaze firing today to 1240deg but from about 1170deg it has been struggling to gain temperature.  And at times it drops up to 10 degrees before it goes up again.

I have two bungs in the holes in the side but not one in the lid.  I'm fairly new to this so not sure if that is correct or not.  Any ideas what the issue might be?  The person I bought it from said that the elements were replaced recently.

I'm not sure what to do now because its been firing for waaaay longer than expected and still not up to 1240.  Any advice for a newbie would be greatly appreciated!

Thanks

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check to make sure the kiln voltage requirements is also the same as whats at the kiln plug in building-like foe example the kiln plate says 240 volts and the building is 208 volts.Keep the bungs in unless you need to look in at cones.

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That kiln's max temp is 1300c, so it should get there.

However, unless the elements are in excellent (think new) condition, and you have a very short cable and are plugged into a socket that goes direct to the fuse board it is highly unlikely to reach that.

 

Are you using cones to judge the firing? 

If it has been firing for longer than you expected, it could  have fired "enough" to mature your glazes, but you will only know that from the end result or from cones..

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lukeseall,  your post reminded me that lately there seem to be a number of folks who have their first kiln whether new or used.  many questions lately include the question of how long a firing should take.  whether stated or implied, many folks seem to think that firings take only a few hours and even turn off the kiln at the end  of only a few hours assuming it has fired too long.  

my question is, where are these bits of information coming from?    is there someone on youtube telling viewers how long to fire things?   

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6 hours ago, Chilly said:

However, unless the elements are in excellent (think new) condition, and you have a very short cable and are plugged into a socket that goes direct to the fuse board it is highly unlikely to reach that.

 

Hmmm...  It is a 32amp plug so it goes straight to the fuse box, although it has to travel quite a long way.  Maybe that is the issue. 

 

4 hours ago, oldlady said:

lukeseall,  your post reminded me that lately there seem to be a number of folks who have their first kiln whether new or used.  many questions lately include the question of how long a firing should take.  whether stated or implied, many folks seem to think that firings take only a few hours and even turn off the kiln at the end  of only a few hours assuming it has fired too long.  

my question is, where are these bits of information coming from?    is there someone on youtube telling viewers how long to fire things?   

Well, the controller allows me to set a deg/hour rate, which I set according to a firing schedule I researched.  So from that I can work out how long firing should take to reach a certain temperature.  Assuming it actually heats up at that rate, which on the Bisque firing it did. 

Is it normal for the temp rise to slow down as it gets hotter?  Perhaps I am being naive to think it would rise at the rate set on the controller?   In the end it was going for 18 hours and hit 1239deg and I switched it off as I didn't want to leave it overnight knowing it might not be functioning very well. 

I don't mind if it takes a long time to reach temperature, but the fact the temperature keeps dropping then rising again suggests to me that it is not right. 

 

 

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2 hours ago, lukeseall said:

 

Is it normal for the temp rise to slow down as it gets hotter?  Perhaps I am being naive to think it would rise at the rate set on the controller?   In the end it was going for 18 hours and hit 1239deg and I switched it off as I didn't want to leave it overnight knowing it might not be functioning very well. 

I don't mind if it takes a long time to reach temperature, but the fact the temperature keeps dropping then rising again suggests to me that it is not right. 

 

 

Mine slows down after it gets to about 1100c.  So probably yes.  I have a smaller kiln than yours, also a Potterycrafts, with the same max temp.  Even with brand new elements it struggles to reach 1260, but will put ^6 down with enough heat work.

 

Have you opened the kiln yet?  Was the firing OK?

If it fired for 18 hours, your pots are probably overfired.  Did you use cones?

 

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yes, it is normal for it to slow as you get to a certain point.   i have a kiln with a controller and it is set for a slow glaze at the factory.  i have used it once or twice to slow cool but i really do not use that feature, i trust the factory setting.  it has 3 thermocouples and i can determine the temperature at the top, middle and bottom of the  kiln as  it fires.   the readout shows the middle temperature and at times the bottom is 20 degrees cooler and maybe the top is a few degrees hotter.    i consider that normal.    normal for my kiln, my kind of work, my packing density.

when it gets near the end of the firing i have watched the readout fluctuate back and forth several times before settling on a particular number of degrees.   it has always fired well for me and maybe i am just too easily satisfied, but for what i do, it works very well.   my user manual discusses the program and the expected slow spots.   having read it once, years ago, i am confident that the factory setting was thought out well.

my concern with all the recent questions is that some sources of information are not as reliable as others.   i do not know where your program came from but some folks think a firing should take only 4 hours and that seems extreme to me.   the size and contents of the kiln, the spacing of items, the age of the elements, the number and type of shelves and posts all play a factor in firing.    someone else's firing schedule may not work for the kind of work you do and the way you pack your kiln.

i hope your results are good and your concerns are just a normal learning curve.

Edited by oldlady
spell

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