Glaze Firing cut out at Bisque temp

[Northen Pots]

Hi everyone,

I've just had a minor electrical emergency which meant I had to shut off my kiln as it reached bisque temp (Cone 04). My fuseboard started to melt but that's another issue...

I'm just wondering if the pots inside will be suitable for refiring if the maturation temp of the glaze / clay hasn't been reached? I'm using high fire stoneware with ash glazes firing to cone 8/9. 

Normally I would experiment to find out for myself, but as I said, the mains supply to my studio is a tiny bit melted so until I can get that sorted my kiln is out of action.

Its currently crash cooling at 900°c and I can hear some slightly worrying popping and cracking noises from the ware inside so I've plugged the peep to slow down whatevers going on in there.

Its my first kiln and I've only fired it 7 or 8 times so any info is much appreciated 

 

Will

[Mark C.]

Most likely it will be fine. 

Not sure that ash firing to cone 9 in an electric is a great idea as it will really shorten element life but yoiu know this already and I assume the kiln is acone 10 model.

If the kiln is sealed up and only went to cone 04 then pots shoule refire nicely  when you get the power issue resolved.

I would love to see the finished work if you can add some photos .

[Northen Pots]

Thanks for the reply Mark.

Im not too versed in exactly how much I'll be shortening the life of my elements by firing this high, and probably don't have a great reason for firing to cone 8 either. I've just been experimenting with glazes and firing patterns and it's where I've ended up. It is a cone 10 kiln, yeah. 

I think now I've found a reliable ash glaze I'll probably see how it works at lower temperatures with a drop and hold pattern to save my elements. 

Here's some pictures of my Matt ash glaze with iron oxide. It came out way more random looking than I had even hoped and has got some really wood-fired effects to it. I've washed parts of the bisque with FeO and sprinkled ash on the wet glaze in parts. 

 

Is there a reason why firing ash lowers the life expectancy of the elements? 

[neilestrick]

51 minutes ago, Northen Pots said:

Is there a reason why firing ash lowers the life expectancy of the elements? 

Firing ash does not affect element life. Firing to cone 8 or above does. In a typical cone 10 kiln firing cone 04 bisque and cone 6 glaze, you'll get approximately 150 firings from a set of elements. Firing to cone 10 will cut that by half or more, and wear out the bricks faster. Most cone 10 glazes can be brought down to cone 6 with the addition of a small amount of boron in the form of Frit 3134 or Gerstley/Gillespie borate, sometimes as little as 3%. While cone 10 glazes are great, what makes most of them great is the fact that they're usually fired in a reduction atmosphere. Since you can't do reduction in the electric kiln there's no good reason to fire them to cone 10. Firing cone 6 will extend the life of the elements and the kiln itself, and lower the firing cost.

Melting a fuse panel is a big deal. Make sure you get that fixed properly!

[Min]

If you do consider moving down to cone six make sure the clay you use is rated as a midfire clay that matures at cone 6. I noticed you are in the UK where wide firing range claybodies are common, for functional ware a cone 10 (highfire) body will be underfired at cone 6 which leads to problems like strength and durability, crazing from moisture, weeping pots  etc.

[PeterH]

Just to reference @Min's point that slow-cooling can effect the characteristics of some glazes (arguably  in a way that happened naturally in a previous generation's highly insulated cone 10 kilns).

 

[Northen Pots]

15 hours ago, neilestrick said:

Firing ash does not affect element life. Firing to cone 8 or above does. In a typical cone 10 kiln firing cone 04 bisque and cone 6 glaze, you'll get approximately 150 firings from a set of elements. Firing to cone 10 will cut that by half or more, and wear out the bricks faster. Most cone 10 glazes can be brought down to cone 6 with the addition of a small amount of boron in the form of Frit 3134 or Gerstley/Gillespie borate, sometimes as little as 3%. While cone 10 glazes are great, what makes most of them great is the fact that they're usually fired in a reduction atmosphere. Since you can't do reduction in the electric kiln there's no good reason to fire them to cone 10. Firing cone 6 will extend the life of the elements and the kiln itself, and lower the firing cost.

Melting a fuse panel is a big deal. Make sure you get that fixed properly!

Thanks for that! I'll experiment with taking the temp down. I think trying to only change one or two variables at a time when glaze testing made me reluctant to drop it down. Pressures of trying to turn a profit and develop new glazes from scratch I guess! 

 

The fuse panel has been upgraded and I think in due course the max current going into the building will be upgraded also. I'm only glad I'm not the one footing the 11k bill for that job . Losing a kiln load of work would be enough cost for me! 

[Northen Pots]

On 7/10/2021 at 7:09 PM, neilestrick said:

Firing ash does not affect element life. Firing to cone 8 or above does. In a typical cone 10 kiln firing cone 04 bisque and cone 6 glaze, you'll get approximately 150 firings from a set of elements. Firing to cone 10 will cut that by half or more, and wear out the bricks faster. Most cone 10 glazes can be brought down to cone 6 with the addition of a small amount of boron in the form of Frit 3134 or Gerstley/Gillespie borate, sometimes as little as 3%. While cone 10 glazes are great, what makes most of them great is the fact that they're usually fired in a reduction atmosphere. Since you can't do reduction in the electric kiln there's no good reason to fire them to cone 10. Firing cone 6 will extend the life of the elements and the kiln itself, and lower the firing cost.

Melting a fuse panel is a big deal. Make sure you get that fixed properly!

The refiring was a success. I changed the firing pattern from a cone 8, no soak, drop and hold, to a cone 6 with a soak and a longer drop and hold. No noticeable differences in my matte glaze but my glossy glaze was more of a semi matte (any insights? Will the gloss be better suited to a higher peak temp and no soak?).

 

It works better that way so can't say I'm disappointed. Pics of some of the better pieces attached.

 

Thanks for the advice everyone.