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shawnhar

Advice for 1st glaze firing?

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Just about ready to do my first glaze firing in a couple of days and looking for some feedback or just a sanity check. I can't bear the thought of ruining an entire kiln load because I didn't do my due diligence or overlooked something simple.

 My kiln is a Skutt KM818, it's much smaller than the 1027's at the studio and I know it will fire slightly different. I'm not too worried about that, just want a semi-safe starting point. My glazes are rated cone 5/6 and are the same ones used at the studio, they were just mixed from dry ingredients 2 days ago.

The studio fires their kilns to cone 5 with a 10 or 15 minute hold, I forgot which, and I believe they said that puts them up right at cone 6. They do not use vents. I am using a vent, and I am planning to use the pre-programmed cone fire mode, medium speed, to cone 5 with a 10 minute hold. No fire-down, turn the vent off after the hold completes. I have cone 5 and 6 witness cones to spread around the kiln.

The only other variable that might have an impact I can think of, is I fired my bisque to cone 06, rather than 04 like the studio does, not sure if that would have a big impact on the glaze firing, but I did read it might make the pieces absorb more glaze when I dip them so I need to be careful about the thickness. I plan to bisque the next batch to 04 and compare (if this 1st glaze firing goes off without a hitch).

Am I overthinking it or is this a solid firing plan? 

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Thermocouples can vary, I would put a cone pack in front of the spyhole and monitor it near the top of the firing. (wearing eye protection) Increase the hold time if necessary to bring the ^6 down. (In my kilns 10 minutes is not enough to go from cone 5 to cone 6)

There is a lot more mass in the 1027 which in itself will slow the cooling down more than your 818, might be fine but might need to add a bit of a slow cool depending on how the glazes look.

 

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Thanks Min, you bring up something I have wondered about. If I see the ^6 is not bending, I don't know how to increase the hold time without starting the whole firing program over. Are you saying "next time" increase the hold time? I am also pretty sure my little kiln will not hit the next cone in 10 minutes, but unsure whether it is better to over or under fire glazes.

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Which controller do you have? With the Genesis you can add 5 minutes while in a hold or increase temp while in a hold.(page 17 of this) If it's an older controller then you have to quickly shut if off then restart it. As long as the temp has dropped below the "set point" for the soak it will restart and go to the last segment. There might be another way but that's how I do it. Can you talk with someone at your studio and confirm what they are firing to? Wasn't sure if you meant closer to cone 5 or 6? If it's cone 6 then I would use the med speed glaze fire to ^6, watch the cones near the end of the firing and shut it down when 6 is down if that happens before the soak. (Can do a tc offset for your next firing to allow for a soak if it's firing too hot) If 6 is nearly down adding 10 minutes would be perfect to get to ^6.

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Ah well, I have the Skutt controller, slightly different than the Bartlett. 

The studio only refers res to cone 6 glaze, never anything else. The owner happened to state they do the soak at cone 5 thing, to hit cone 6, to even out the kiln. 

You recommend setting to ^6 with a hold and just shutting down if the ^6 cone hits the shelf? That sounds like a better plan, and get to see the TC offset based on what the cones do, perfect!

Why would you allow the soak to continue if the ^6 has already hit the shelf, rather than shut down then, did I read that wrong?

 

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I would just do a cone 6 firing and see how it comes out. If it's too hot or too cold, I would then adjust the TC offset to get it dialed in. A 10-15 minute hold will not get you from cone 5 to cone 6, so the studio kilns have some calibration issues.

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I think no matter what, you'll be figuring out things on your own by firing.  I do gas but I'd imagine it's the same with electric.  Sometimes you screw something up and stuff gets ruined or underfired or bubbly or whatever.  Make note of what happened and look up on digitalfire on what it might mean, adjust and retry haha.

One reason I use the same clay body over and over is because I have so much time invested in adjusting glaze and firing schedule for this one body that it will take a miracle for me to have enough time to invest in another one.

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I have that kiln and fire my Cone 6 glazes to Cone 5 with a 15 minute hold. Works perfectly. The school I used to fire my work at had huge Skutt kilns, and my results are identical. I think you’ll be pleasantly surprised. I let the kiln cool naturally, so it’s faster than the larger kiln but it has not made a difference in my results compared to the larger kilns. Good luck! 

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5 hours ago, shawnhar said:

You recommend setting to ^6 with a hold and just shutting down if the ^6 cone hits the shelf? That sounds like a better plan, and get to see the TC offset based on what the cones do, perfect!

Why would you allow the soak to continue if the ^6 has already hit the shelf, rather than shut down then, did I read that wrong?

Yes. If this happens then note the temperature when you shut it down.

If the cone isn't down all the way at the beginning of the soak I would let the kiln continue with the soak. If the cone tip gets to about the 3:00 o'clock position (or 9, depending on which way it's facing) adding a 10 - 15 minute soak probably will take it to tip touching shelf.

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I saw you have already fired in another thread. If I were you I  would stop using your pots to work through all of this. A new kiln and entirely new set of mixed glazes requires some testing. Neil and others can correct me if I'm wrong but no you should not get much different results from the 1027 and yours. I use a small 1cf kiln for glaze testing and production happens in either a 1027 or oval 9cf SPS kiln and the glazes turn out about the same, at least to my eye.  They all have the same controller with same schedules and controlled ramp cooling.   

If you just can't bare to spend time testing with test tiles then just throw 50 spoon rest (nice flat surface and walls to see the how the glaze breaks) or a bunch of small snack bowls. Why toss a bunch of nice pots into an unknown.

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Thanks Yappy and Stephen, just waiting for my test pieces to dry so I can do another bisque and then I will use those at ^5 with no hold, go from there. I have enough to run 4 test fires and hoping I will find the sweet spot.

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On 9/27/2018 at 9:51 AM, Stephen said:

I saw you have already fired in another thread. If I were you I  would stop using your pots to work through all of this. A new kiln and entirely new set of mixed glazes requires some testing. Neil and others can correct me if I'm wrong but no you should not get much different results from the 1027 and yours. I use a small 1cf kiln for glaze testing and production happens in either a 1027 or oval 9cf SPS kiln and the glazes turn out about the same, at least to my eye.  They all have the same controller with same schedules and controlled ramp cooling.   

If you just can't bare to spend time testing with test tiles then just throw 50 spoon rest (nice flat surface and walls to see the how the glaze breaks) or a bunch of small snack bowls. Why toss a bunch of nice pots into an unknown.

The one thing I will say is that we do cone 5 with a 20 minute hold to allow the melt to even out and reduce glaze defects such as pin holes. The extra 20 minutes bends the 6 cone about half way with heat work.

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Perfect info man! I am guessing that is what I will get with cone 5 and no hold, based on my previous result, if so I can put in a cone offset and add a hold, hopefully that will get me in the ballpark.

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