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Celia UK

Bisque Firing ?temperature Reached

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Good morning all! Just opened my small electric kiln after a bisque firing. It was programmed - 100oC per hr to 600oC then 200oC per hour to 1000oC. I had 03 04 05 cones in a pack (really needed 04-05-06 but had this one to hand) on the bottom shelf and an 04 mini bar in the kiln sitter.

 

The temperature was rising as expected early on, but slowed down at the upper end, so overall took about 10 hrs. No error message on the programmer.

 

The work appears bisqued, but none of the cones, nor the minibar have changed in the slightest!

Some small test pieces were glazed (Once fire) on one 1/2 with a low fire transparent (matures at 06-05) which looks fine.

 

Any suggestions as to what is happening here?

 

Is there anything I need to consider when glazing these pieces - all will be transparent, shiny glaze.post-13648-0-79416100-1450517873_thumb.jpgpost-13648-0-01679900-1450517937_thumb.jpg

post-13648-0-79416100-1450517873_thumb.jpg

post-13648-0-01679900-1450517937_thumb.jpg

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C06 is 1000Deg Centigrade 03, 04,05 are all higher than this.  so Your cones are working OK! How are you using the minibar when you have  a controller? I used to use minibars on my kiln sitterfor my old kiln  which was manually operated? SO do you have a controller AND a kiln sitter?

Do I understand that you correctly that you  were bisquing to 1000C?

You should have to do nothing different when glazing your pots, which are exquisite!

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Hi Babs. That's all very reassuring! I hadn't looked back at my cone chart to check the correlation, but expected some movement on the 05 cone at least! I was bisquing to 1000oC and do have a controller and sitter. The sitter is just a back up, as the timer override no longer works. It's belt and braces really - and at least gives me more info on how the kiln is firing.

Thanks for your comments on my pieces - it's the next stage that will determine the final outcome. Hopefully the black & white triangles one will be successful as it's a present for a friend who has a chair upholstered in fabric of this pattern!

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The bowls are great!

 

Seems like your kiln shouldn't be having trouble coming up to cone 05 at 200C/hr. Is this something new with this run?

 

I always tip the edges of my bisque fire pieces to see if they ring. If they do, they are probably OK.

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Well the temperature reached is often different to the cone movement as the cone reflects heatwork done. so if you are doing a slow firing as opposed to a rapid firing the cone will bend at a different temperature, check the Orton site , this info used to be on the sides o f the boxes the cones came in. Quite a difference in temperature required to bend the cone at a rapid firing.

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Quite a difference in temperature required to bend the cone at a rapid firing.

 

This is very much true, there is much less heatwork getting to a temp quickly than slowly. That is why Orton has different temps for different rates. If your programming your own schedule you should pick a rate near the top cone you want for at least an hour so that your cones will be pretty accurate.

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I love the one with the black& white triangles. How did you get them so neat?

White underglaze all over then Small paper triangles cut out, dampened and laid in position as resist. Black underglaze and the other colours painted in triangular spaces left. Carefully lifted paper triangles and a little tidying up when dry. Very satisfying if you like this sort of fiddling!!

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Seems like your kiln shouldn't be having trouble coming up to cone 05 at 200C/hr. Is this something new with this run?

 

I haven't regularly been in the habit of setting up cone packs, so have always relied on the digital controller. If set to 1000oC and it switches off after an appropriate time without throwing up an error message, I've assumed it got to 1000oC. Possibly it's the 'heat work' business?

 Everything has a nice ring to it!

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The discrepancy between temp and cone bend will "show" more when glaze firing, some glazes won't "do it" until the cone bends, a soak at the end of glaze firing can bring glazes to the required state.

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