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Celia UK

Urgent Help! Electric Kiln Error / Mistake?

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Had a full glaze load in my Nabertherm electric kiln (my first glaze firing in it). Programmed to 1200oC with a 10 minute soak at the top. However, without me realising it has sat at 861oC for the last 12 hours! I don't know why it has held there, but I suspect I somehow put in a different program number (previous owner used it for onglaze firing and there was a program set for this) and not the one I'd set for my firing. I now have to wait for it to cool to see the damage. Or do in need to let it cool at all?

 

Any advice on what to do next? Can I just start it again and go to 1200oC or will that total up to too much heat work???

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Ohh , I am absolutely paranoid now, about to get my new kiln with controller . First time with one of these beasts.

I am wondering if I can fiddle during firing ie override programme without stuffing up the computerised controller.

Celia, good luck, I have no idea what 12 hours at 861 would equate to, but there will be no carbon stuff left in your clay!!

How long was you firing scheduled for?

What size is the kiln?

12 hours seem a long firing if not going to stoneware temps. Or was this part of the error.

Does the kiln have a cut out after a certain time ie slightly longer than the anticipated firing?

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You can override the program with most controllers, which is fine if you're watching it. But given that one of the advantages of the controller is that you don't have to keep a close eye on it, this isn't always helpful ( as in my case)!

The program I THOUGHT I'd set would have been about 9 hours total. The first time I looked and it (after about 7 hrs) was at 860oC I presumed it was on the way up, then when I checked later (about 10 hrs) and it was about the same, I assumed it was on the way down! Sounds really stupid now, but the times were about right and I had no notion it wasn't just proceeding through the program I thought I'd set it to!

It's a 60 litre kiln. I'm sure there would be a cut out if things aren't doing what's programmed, but I suspect it was doing what the program had in it (as I said, not my program and not one I've even looked at - I can check later)

 

I don't know how to work out what temp to refire to??????

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I'd refire to normal temp or just below .Your glazes usually stable, ie no runny ones?

I feel that at 860, not much happening in glaze maturity of a cone 6 glaze.......

Hope you get some expert shipping in.

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Only time my kiln did anything like that was when a relay burnt out. Does it smell like burnt electrics at all? Possibly an element out. Not sure why you would make a program with a 12 hour hold but I don't know much about onglaze firing.

 

Most modern controllers would cut out I think but my relay fused on so bypassed it. I think it actually took an element out in the process, or the element went and took out the relay too.

 

If it was a program and no fault with the kiln then no problem, you will have bisque the glaze to the pots if didn't go anywhere past 1000.

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Hi Joel - no smell - all fine on that front. I agree about 12 hour hold. There's a possibility I messed up this program when I first got the kiln and spent ages trying to work out the programming sequence, but not sure how it went off my chosen program on this occasion. I've bitten the bullet and just reset to go straight up to 1200o now, so as not to 'waste' the 800o it was at. No peepholes in Neberterm kilns so I can't even look at the cone pack. As the glaze had a range up to 1280oC and I'm only going to 1200o I'm hoping that it won't be over fired. But who knows? And how could I ever calculate how much more it needed anyway. I'd bet my bottom dollar if I waited for it to cool before refiring that it would be under fired - what do you think? Am I being foolish and impatient? Shall I switch off?

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So was it on exactly the same temperature both times you checked? Just want to make sure it has not actually fired quite slowly and has been the correct temps when you happened to look. Was it on both times, switching the relays?

 

There is no peep hole you can shine a torch in to make sure you have not actually fired the pots? Open the lid a tiny bit to see if they are shiny?

 

If they are bisque then no reason no to go from 800 to 1200 but keep a good eye on it  :P

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Same temp +/- 1/2degrees at 7.30pm 9pm and thus morning at 8am. Not sure what switching the relays means Joel!

No peepholes at all and I'm loathe to open the lid at this temp - cold gush of air in from garage!!!

 

What exactly does keep a good eye on it mean? I won't be sitting in the garage all afternoon ! I've banged it on 250o/hr to 1200 now and it's behaving as I'd expect.

 

Problem is getting to know the controller well enough to know how to advance it during firing and also check the program during firing, without messing it up. The German translation seems to use different terminology to that I'm used to and simplified instructions are elusive on the net!!

 

Fingers crossed!

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Ok sounds like it just stopped there then. Just wanted to make sure you were not double firing your pots. Switching the relays means turning the power on and off to the elements. The clicking noise is a relay switching the power on and off.

 

Keep a good eye for me means making sure it is doing what it should be till the end. No need to sit in the room but a check every hour or so.

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Ok, so here we go! Couldn't keep an eye on it all afternoon but before I HAD to go out I was reassured to see that it was into the 900's and I expected to see it at the top or on the way back down again when I came back. However, it was once again hovering around 884o then 890o then down a few degrees etc. I looked into the firing history and it told me that the maximum it had reached was 915o. The fault history told me it was not reaching the configured temperature - which I knew by this time! I'm now leaving it to cool down so I can take a look inside.

 

Does this sound like an element or relay or something else? Think I'll unload it and refire in 2 batches in my little kiln, but to what temperature?

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Second hand but not much used and in immaculate condition. The lady had a little ceramics decorating business - parties where people decorated ready made pieces and she then fired them. Have emailed kiln technician to call me tomorrow, so he may have an idea once he's looked at it. Thank you for your thoughts!

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Just a whole load of 'stuff' Babs. A few plates, bowls and mugs, some ring dishes & spoons and a mug and little pinch pot that 2 of my grandchildren made back in the summer. I'm still at the 'trying things out' stage of my ceramics hobby - even after 3 years fiddling around! Thankfully I procrastinated so long about applying to exhibit at our region's Christmas selling exhibition (would be first go at such an event), that all the places were filled. Otherwise, this kiln load would have been for that and I'd be in a complete stress! As it is I might need to think again about a best friend's 60th birthday present and Christmas presents for some friends and family.

 

Who knows - I may be lucky and can still retrieve something and try a third firing? I'm staying optimistic until I know otherwise for certain!

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Same temp +/- 1/2degrees at 7.30pm 9pm and thus morning at 8am. Not sure what switching the relays means Joel!

No peepholes at all and I'm loathe to open the lid at this temp - cold gush of air in from garage!!!

 

What exactly does keep a good eye on it mean? I won't be sitting in the garage all afternoon ! I've banged it on 250o/hr to 1200 now and it's behaving as I'd expect.

 

Problem is getting to know the controller well enough to know how to advance it during firing and also check the program during firing, without messing it up. The German translation seems to use different terminology to that I'm used to and simplified instructions are elusive on the net!!

 

Fingers crossed!

 

Had a full glaze load in my Nabertherm electric kiln (my first glaze firing in it). Programmed to 1200oC with a 10 minute soak at the top. However, without me realising it has sat at 861oC for the last 12 hours! I don't know why it has held there, but I suspect I somehow put in a different program number (previous owner used it for onglaze firing and there was a program set for this) and not the one I'd set for my firing. I now have to wait for it to cool to see the damage. Or do in need to let it cool at all?

 

Any advice on what to do next? Can I just start it again and go to 1200oC or will that total up to too much heat work???

The 12 hour soak may have brought you to cone 07, which may not of hurt anything.  If the controller has a review button press it and you will see what the program is.  You can change the program to what you want and if the kiln is still hot the program will take off from that point.  So you don't have to wait for the kiln to cool down.  I may not be correct about this so watch the kiln to see if that is really happening.  It is always a good idea to press the review button to see if the program is as you wanted  it.

David 

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Thanks David - I did try to 'pick up' the firing from the point it had reached but it kept defaulting to 'wait' mode. When I read the handbook carefully I found that if the temperature of the kiln is higher than the starting temperature of a program (even if the controller is moved to the right firing segment), the kiln goes into 'wait' mode until the temperature falls to below the starting point. Which is exactly what it did. Just a feature of this kiln I guess. Knowing this, I just programmed in a 250oC per hr rise to 1200oC and set it off.

 

Anyway as the same thing happened as the first time, I switched off and have just opened the kiln (see photo) - everything just smooth and white as it went in.

I've contacted the kiln engineer and in the meantime will unpack and load what I can into my smaller kiln and refire to 1200oC. Offer up a prayer to the kiln gods for me!!

post-13648-0-83508000-1447058934_thumb.jpg

post-13648-0-83508000-1447058934_thumb.jpg

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Thank you! I used a ceramic nibbles bowl as a slump mould and the flower was from a silicon mould used for cake icing! Discovered that my nearby kiln technician stocks the German kiln I've been having trouble with, so is familiar with it! Coming out Thursday.

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Aaaggh! The kiln gods weren't listening! Old Lady - Now I know why I need a peephole and why I should peep into it!!!!!!!!!!

 

All the pieces in my little kiln have over fired and the glaze has crawled - in some cases right off the pots on to the shelf! The thicker the glaze the worse the crawling. Bizarrely the little kiln appears to have over fired too - all three cones - 3,4 & 5 (I know I should have had 4,5&6 but ran out of 6's) were completely slumped over. This was a new cone pack, not the one that went into the previous firing, in case anyone asks!) However, the cone 6 minibar in the sitter, while almost at 90o angle hadn't gone quite far enough to trip the switch.

 

So now my dilemma is what to do with the other half of the load from the big kiln, that has already had 2 firings?? Any advice would be most welcome here. I will (reluctantly because I'm going to hate showing you all how bad this has turned out) post pictures of the cones and two of the over fired pieces - a worst (thicker glaze) and no quite so bad (thinner glaze).

 

I know I'll have your sympathy, but also any advice would be most welcome.post-13648-0-24725800-1447150487_thumb.jpgpost-13648-0-88384000-1447150503_thumb.jpg

post-13648-0-24725800-1447150487_thumb.jpg

post-13648-0-88384000-1447150503_thumb.jpg

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Looks like you probably hit a near perfect cone 6. So I wouldn't say it over fired if you were going for cone 6. When you say little kiln, how little do you mean? I've got a little 1 cubic foot test kiln, and glazes do all sort of weird things in it because it fires up and down so quickly.

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Small kiln is 40 litres - 1.4 cu feet Neil. Fairly typical hobby potter's kiln over here.

 

Yes Babs - no problem with the clay/glaze combination before. I'm thinking that perhaps the long firing at 880oC - about 12 hours in total, added up to sufficient heat work to vitrify the clay, which prevented the glaze from adhering. Does that sound feasible?

 

With the remaining half load, that has also had the long 880oC firing - if my theory above is correct and the clay has vitrified already, could I try to remove the (half fired) glaze and reglaze with a low-firing glaze, or would vitrified clay take any other kind of finish??

 

Any suggestions, most welcome!

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