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Another KM1227 question

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This may be more clay related, but I recently purchased a 1227 that is in great condition (brick and elements) but going through the motions of replacing relays/wiring harness and thermocouple. I did test the elements resistance and they're about brand new.

The first firing I paid no attention and loaded ware for a bisque (06). After 14 hours I realized I should've checked the relays.. I turned the kiln off at about 1630, and did the relays and harness. Since I got through some quartz inversion after replacing relays and harness I went ahead and fired the kiln again, this time 06 and medium with a 5 minute hold. The kiln fired in 7 1/2 hours and my cones did not drop. In hindsight I should've done the thermocouple, but I've been in a rush to get out orders and just went for it.. 

Anyways, my question is - I'm replacing the thermocouple and want to get these pots to a bisque temp but 1) Im thinking of firing to 05, and 2) will all these firings effect the hardness or clay body?? 

Sorry if any of that is confusing.. Thanks!

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Good questions!

All those hot hours - the organics and such should be well burned out by now. If the ware will take glaze in about the same fashion that you are used to, would you consider just glazing and firing? err, glaze a few representative pieces and glaze fire them along with your next load?

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Thanks for the responses and advice!

I was impatient and decided to fire everything a 3RD time. The good news is that all my cones dropped and the new thermocouple seemed to be the ticket. Gives more peace of mind for a glaze fire. Let's hope everything isn't over fired and glaze sticks to the ware. :unsure:

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On 9/16/2021 at 1:26 PM, brettwulc said:

Since I got through some quartz inversion after replacing relays and harness I went ahead and fired the kiln again, this time 06 and medium with a 5 minute hold

Just a couple observations FYI - Clay goes through quartz inversion up and down. For a glaze firing if your load has stopped let’s say within 300 degrees or more of its firing cone temperature then little heatwork was likely done so refiring  generally is not an issue. For bisque you can bisque fire pretty much as many times as needed within reason. Finally to make your cone drop at the temperature advertised on the cone chart, fire at the appropriate speed per the chart for the last 200 degrees. So for cone 6, center column (108 degrees per hour) fire to 2232   Starting at 2032. If you can fire per the chart, you stand a good chance at nailing your cone. Holds at top temperature can cause issues, do them only when you have a real confirmed reason to..

Bisque firing only sinters  the clay together so not much melting. Bisque firing generally take longer to burn everything out so time at temperature is important. Many bisque firings range from 10-12 hours just to be sure to remove all organics.

Quartz inversion just happens, up and down. Clay is tough, it generally can take it. Not much we can do about it.

Typical glaze fire speeds 400-500 degrees per hour

Typical Bisque speeds  approximately 200 degrees per hour

Hope that gives you some ideas for future use.

Edited by Bill Kielb
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