Dawn Raburn on wed 5 sep 07
Just unbricked my 5th gas firing and there doesn't seem to be much if
any reduction. I am sick. I know, I am no expert on this with only
5 firings, but my first, third and fourth firings were pretty good.
I can't really duplicate those firings because I was dancing all over
the place with my gas and air. I did take notes but still, it was
crazy. Well, this time I did what is so often recommended, to work
up to full air, full gas, and use the damper for control. Started
body reduction at 012 and I had flames 16" out the top and probably
8-12" out the bottom peep. Then during the rest of the firing I was
still getting 8" flames out the bottom peep and more up top. So,
what the heck? Do I re-fire the same wares? Will that weaken the
body? Will it do any good now that the clay is vitrified? I've got
shows coming up!
I have written before, but just so you know, I have a brick,
downdraft forced air approx 37 sq ft kiln with natural gas.
Help,
Dawn
Bob Johnson on wed 5 sep 07
Dawn:
I'm no expert on the fine points of reduction firing, but I can share what may be a similar experience---and how I solved it.
In my first year or two of firing my downdraft kiln, reduction was spotty at best, absent at worst. I did what seemed to be all the right things with the damper; flame came out of the peeps---but reduction was not good.
After a lot of reading and talking to other potters I finally figured out that I was setting my flame too clean and efficient with the primary air, so there just wasn't enough carbon (carbon monoxide, actually) left to do a good job of reduction. The solution: making the flame just a bit yellow, which lets some of the unburned fuel circulate through the kiln.
If that works for you, tho, beware of going to the other extreme and getting too much reduction, with carbon coring (which is what I did).
Bob - Southern Oregon
At 9/5/2007 05:28 AM, you wrote:
>Just unbricked my 5th gas firing and there doesn't seem to be much if
>any reduction. I am sick. I know, I am no expert on this with only
>5 firings, but my first, third and fourth firings were pretty good.
>I can't really duplicate those firings because I was dancing all over
>the place with my gas and air. I did take notes but still, it was
>crazy. Well, this time I did what is so often recommended, to work
>up to full air, full gas, and use the damper for control. Started
>body reduction at 012 and I had flames 16" out the top and probably
>8-12" out the bottom peep. Then during the rest of the firing I was
>still getting 8" flames out the bottom peep and more up top. So,
>what the heck? Do I re-fire the same wares? Will that weaken the
>body? Will it do any good now that the clay is vitrified? I've got
>shows coming up!
>
>
>I have written before, but just so you know, I have a brick,
>downdraft forced air approx 37 sq ft kiln with natural gas.
>
>Help,
>Dawn
>
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