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akilspots

converted electric to gas kiln results

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from the first firing of a little electric to gas conversion kiln i built.  hit cone 6 at the top and middle of the kiln and cone 7 at the bottom where the burner port is. 

had some mixed results:

  • one glaze blistered pretty badly on everything it was on.
  • some shivering on the inside of one bowl where i used the "gold" shino. 

 i re-fired these 2 of them in the same kiln and 1 in an electric and they all healed over the 2nd time around...

 

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Nice work, at 1500 degrees your firing rate actually increased so I would guess it was not in heavy reduction. Nice graph, looks like no issue to make cone six.

you may get some useful info here with respect to simple reduction 

 

 

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16 hours ago, Bill Kielb said:

Nice work, at 1500 degrees your firing rate actually increased so I would guess it was not in heavy reduction. Nice graph, looks like no issue to make cone six.

you may get some useful info here with respect to simple reduction 

 

 

yeah i actually watched this video a few times...definitely got some good info from there.  it's very sensitive to changes i guess from being so small. so its like i can get a reducing flame coming from the chimney but a slight adjustment of the damper will have it climbing while there's a reducing flame as well. it never gets quite as big as that one in the video still though. but the klin is just a little 4.5-5 cu ft baby kiln. it has been great to get some firing practice with though.

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15 hours ago, neilestrick said:

Are you using commercial glazes? If so, they are intended to be fired in oxidation, so may or may not be happy in reduction. Nice results overall, though.

they are all from john britt's mid-range glaze book. the shinos definitely want to be fired in reduction not so sure about the oxblood glaze i've got mixed results with it in both types of firings. 

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2 hours ago, akilspots said:

yeah i actually watched this video a few times...definitely got some good info from there.  it's very sensitive to changes i guess from being so small. so its like i can get a reducing flame coming from the chimney but a slight adjustment of the damper will have it climbing while there's a reducing flame as well. it never gets quite as big as that one in the video still though. but the klin is just a little 4.5-5 cu ft baby kiln. it has been great to get some firing practice with though.

Here is a suggestion many find easy and logical to follow that you can try:

Achieve your desired firing rate midfire  say 450 degrees per hour (6-8 degrees per minute) or what you are comfortable with. Set your damper for best balance / energy use..... around 1200  -  1300 degrees.  This will be termed a neutral kiln, still in oxidation  but  sucking in the least amount of secondary air required.  No jets at the site ports not too tight but not crazy loose either and leave it alone from there.
This is usually easy to determine as you slowly close the damper flames will begin to come out of the various ports and openings as the kiln becomes slightly pressurized from the top down. Find the easiest point where it comes out and open the damper gradually so this location is neutral,  (flame just retreating into the hole) all other locations should be neutral since this is the most sensitive one. At this point your kiln should still be in oxidation and nearly as neutral in pressure as practical and sucking in the minimum amount of secondary air as necessary for your kiln to operate in oxidation while efficiently keeping as much heat in as practical.

Then at body reduction time 1500 and above, see if you can push into heavy reduction increasing  gas pressure only,  slowly,  and insuring you have a flame or jet at upper and lower site ports. The lower site port should  have the smallest jet and will be a decent indicator if you are  effectively reducing. Try and set the top flame for a yellow wispy look but if you see raw soot or carbon that would be too much, not necessary.

Follow your Britt schedule or whatever schedule you like and decrease reduction levels later per your schedule  first by slowly lowering the gas pressure. If your temperature rise or speed of firing is not adequate then open your damper ever so slightly while increasing gas pressure But maintaining your desired reduction. At any point during reduction if you lose your jet at the bottom port you are sucking in air or oxygen which can reoxidize  already reduced stuff.

Not sure if that all makes sense but we hope to have a basic video in about a month detailing the above actions for a Geil downdraft that we just finished a monitor for and are currently testing. The principles are the same and the hope is to give folks an initial Easy way to do this and from there they can explore and develop their own methods hopefully sharing results back with the pottery community.

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