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Electric Kiln Firing Help


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Hello everyone.. I hope you will be able to help me!!

 

I am returning to pottery after over 30 years. I have purchased a small electric kiln which has a kiln sitter attached. The kiln has a dial to set ramps and the kiln sitter has a dial to set firing duration. I have read lots about firing schedules but would like some practical advice please.

Could someone please explain a basic bisque firing.. What cone I need, firing duration and ramp setting.

 

I am hoping I have made sense and thanks in advance😊

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Most fire to cone 06, 05, or 04 for bisque firing.  If you kiln is manual, you should be cones for those temperatures (self-standing, large are easy to work with) so you can monitor temperature.  If the dials are L/M/H, then start 2 hours low, increase to 2 hours medium, then high until the tip of the cone you are trying to reach (say, 05) touches the kiln shelf.  Then turn off. 

 

Some more details on your kiln would allow us to provide better information -- size (cubic feet), brand/model, type of kiln sitter, etc. 

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My kiln is a Cromartie Hobbytech 40 with a Dawson kiln sitter. There is a dial HOURS OF ESTIMATED FIRING TIME which I'd marked with numbers 1 thru 20. Then there is a smaller dial marked with SET then numbers 1 thru 9 then HOLD which I understand is to set the ramp. There are also are two red lights marked HEATING AND IDLE respectively. I should say, that I bought the kiln from a friend.. It's about 15 years old but has never been fired and is as new.. I have tried to upload pics for you but without success!! It's a kiln suitable to run in the home.. Thought this would be a good start..

 

Have set a kiln room up and have noted all safety stuff.

 

I was advised to buy clay to suit the temp capacity of my kiln.. It says 1300 max so have bought Potclays ox St Thomas 1150 ~ 1280.

 

Initially, I want to make tiles.. I have done this before.. After 30 plus years am trying to dredge my memory for information!! At that time, I made my pottery but it was whisked away by someone far more competent than me, fired and returned for the next stage etc..

 

thanks for your help

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tanya, what country do you live in?  i suspect the british isles somewhere because of the potclays reference.  you will be able to fire your kiln correctly but there is a word you are using that has a completely different meaning than you believe.  your kiln is not the newest kind which has a computer running it.  you have a temperature and time control which will work fine for making tiles.  there are recent discussions of how to use the timer on one like yours.

 

the word "ramp" as it is used here in discussions refers to an electronically controlled computerized kiln, not yours.  many of us use this kind of kiln and the programs that the manufacturer set up to fire clay into pottery.  they are the basic programs.  some people want to control aspects of the firing with different speeds or temperatures, holding a particular temperature for a longer period than the basic program.  the word "ramp" refers to the way these changes are set up for that particular kiln or that particular firing.

 

if you will look up "kiln" on a supplier's website and look at the photos of kilns, you might find something similar to yours.  you will also see the ones that i  mentioned above.

 

have fun making lots of beautiful tiles.

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The sitter does not set firing duration. It is simply a countdown timer that will turn the kiln off when it hits zero, regardless of whether or not the kiln has reached temperature. It's a safety backup in case the cone doesn't shut down the kiln.You'll need to do a firing with the timer set too high, like 15 hours, to figure out how long a firing takes. Then set the timer for about 1/2 hour longer than that for all future firings. That time will be different for a bisque than for a glaze firing. You'll want to bisque to around cone 04.

 

The clay you have purchased seems to be a cone 10 clay. You really don't want to fire that high in an electric kiln unless you have to, which you don't. Going that hot will burn out your elements much faster, and wear out your kiln much faster. Most folks who fire electric kilns fire to cone 5/6. You'll want to get a clay that matures at cone 5/6, not cone 10. The range of temps they show for you clay is misleading, because the clay will not be fully vitrified if you fire at the low end of the range.

 

For the firing itself, most people put the kiln on low for an hour or two, then medium for an hour or two, then high until the cone drops. You can estimate that by the numbers on the dial.

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AH............  it is not an electronically controlled kiln.  you got a great kiln and only need reassurance.  it is mechanically operated and shuts off in response to a mechanical action, the softening of a cone.   read about cones at the Orton website.

 

instructions for firing it are simple.  see neil's post above.  the kiln is simply like a giant hair dryer that you need to turn off when the hair is dry.   to tell if the pots have reached the necessary temperature and length of time, you put a cone on the bars of the sitter and turn the kiln on.  you choose the cone you want to use depending on what your clay needs.  read neil's post again knowing that you are not setting a timer for something like an oven that will turn off when that timer says to, you are trying to guarantee that the kiln will turn off when the cone melts.  the timer is a SAFETY mechanism to turn it off so you do not burn your house down in the unlikely case of the cone not working correctly.  odds are so great in your favor.  

 

use a mini-bar cone instead of the tapering kind in your sitter.  there are lots of posts on the forum about firing with a cone in a sitter.  sometimes referred to as a sEtter, not sitter.  just a misspelling not a separate term.

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Thanks everyone for your help.. I have all manuals and have read lots and lots about firing my work.. I just needed some practical advice which you have all given formal manuals don't tell you everything!! I will let you know how I get on. I live in the north of Scotland miles from anywhere so there are no good retailers where I could pop in for advice etc which would be so much easier!! Thanks again.. If anyone thinks of anything else I would be glad of any further advice!!

 

 

Tanya xx

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Welcome Tanya - I too have a Hobbytech 40, but with a slightly different Kiln sitter. I was also in the situation of having the work whisked away when I was learning years ago, so had massive holes in my knowledge and understanding when I came back to it! I have had a digital controller added now, but I fired the kiln just with the sitter for about a year, but was only using earthenware clay. I've recently started using some stoneware and have fired it to 1200oC but no higher. As Neil says, although these say they fire to 1300oC that would really be pushing it! Even though I've never tried going that high, I know that it would be very slow to achieve the last few degrees to reach the top temperature.

First time firing, as Neil says set the timer to high number and see what it stops at when the kiln switches off - the difference will be the length of the firing, so you can set it a little longer as a safety net thereafter. I have to say, on mine, the timer knob tends to stick so doesn't really give me an accurate picture. (not needed now I have the controller, but I still have to make sure it's set for longer than the firing will take)

Use minibars in the kiln sitter - an 04 or 05 will bend and switch the kiln off just fine for a bisque firing of around 1000oC. If you make up a cone pack with 3 cones, say 03, 04 and 05 and run it with an 04 minibar in the sitter, you'll be able to see how closely they relate. (Can't believe I'm giving this advice, as I've never got into the habit of using cone packs myself!) I'm sure I've read somewhere to use a minibar one cone lower than you want to fire to. So an 05 in the sitter may actually relate to an 04 firing. Before I had the controller, I used 05 minibars for bisque but I have a friend with the same kiln who uses 04! The higher the bisque temperature, the less absorbent the clay will be for glazing.

I have always found the technical experts at Potterycrafts and Potclays very helpful with queries about glazing and firing, so a 'phone call there with a specific question is another option for you. Better still, someone at Northern Kilns (Google them) would be even more appropriate. If you're using commercial brush-on glazes, although they're relatively expensive, I'm sure you and your Hobbytech will get on just fine. It all gets a bit more complicated and frustrating if you start mixing your own (she says from experience!!!!!) but stick with it and you'll get there. Lots of Googling and questions here .......loads of expert advice to draw on. Enjoy!

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Thanks Celia, it's always good to know you are not the only one!!!!! That's brilliant help.. I think I need to get a lower firing clay so will call Potclays and ask their advice for this. The one I have starts at 1150 to 1280 which I am told will fire a bit high for my kiln. I can't wait to get going and I expect lots of trial and even more errors are in store for me, all part of learning. Thanks again.

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  • 3 weeks later...

If cone 6 Clay is over fired to 2022F will it still take a glaze? L & L kiln overfired during "slow bisque"

Have a call into company, but thought I'd see what the forum thought about over firing.

 

Depends on the clay. What cone did you program it to fire to?

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This is not about firing times, but will hopefully help folks to position the cone or mini bar correctly. 

 

(There is "Kiln Loading" section in the front, with cone info in the back.)

 

If your cone is not set right, the whole load could mess up... (overfiring is one typical problem).

 

(I put this together years ago for my students {and teachers} who were getting their own kilns that had kiln-sitters.)

 

See PDF.

 

Luck!

Lena

Kilns and Cones, a Simple Guide by Lena Arice Lucas.pdf

Kilns and Cones, a Simple Guide by Lena Arice Lucas.pdf

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A problem I have been having with my cone packs is that it seems no matter where I place them--front, back or middle (leaving a clear sight path) once it fires red hot I can almost never get a good clear look at them (yes, I use safety glasses). If I am lucky I can see partially see the shape of maybe one cone of the 3, dimly, but so far it has been a crap-shoot as to what state the cones are in, on both levels (2 tiered L&L). Any suggestions? PS I am developing mild cataracts in both eyes...any chance that is the problem? 

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A problem I have been having with my cone packs is that it seems no matter where I place them--front, back or middle (leaving a clear sight path) once it fires red hot I can almost never get a good clear look at them (yes, I use safety glasses). If I am lucky I can see partially see the shape of maybe one cone of the 3, dimly, but so far it has been a crap-shoot as to what state the cones are in, on both levels (2 tiered L&L). Any suggestions? PS I am developing mild cataracts in both eyes...any chance that is the problem? 

 

http://ncclayclub.blogspot.com/2013/11/when-grandpa-cant-see-cones.html

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Lee, are you using a green or blue tinted lens? I find the green #5 welders lens really works well, I have a darker one too and it's nearly impossible to see the cones at ^6 with that one.

 

 

I sometimes paint a very thin stripe of black ceramic ink or underglaze down the length of the cone, it really pops out and is easy to see. Can you put your cone packs in so there is an element behind it? Easier said than done but if you can that helps too.

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I do have the welder's green but I think the black stripe may help-sounds like a good idea, as well as placement in line with an element.  Thanks  :)

 

Definitely try in-front of the elements, but means leaving a clear space all the was across the kiln.  Does work tho'

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  • 1 year later...

Hi Tanya, I have just purchased a Hobbytech 40 kiln with sitter like yours and was wondering if there was any update on how you've been getting on with yours? Which clay did you find best in the end?

 

I have some school buff earthenware clay and some Duncan brush on commercial glazes that fire to cone 06 according to the bottles! I was wondering what cone to fire the bisque firing to in order to do the glaze firing to cone 06 afterwards if you or anyone could advise, please? Many thanks in advance!

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