Unloading Day October 9 2010
Unloading Day, October 9, 2010
The original plan was to fire this load of pots to C/11 at the front of the kiln and C/8 at the back. It proved difficult and, as a result, we
took the front up to C/12+ in order to get the back where we wanted it. Appropriate clays were used in different parts of the kiln;
anticipating a 2 -3 cone differential in temperature.
At first, everything looked fine. There were many fine pots that came from this firing. This one, at the back and at C/9 half down
displayed "the best of dunting." This was in spite of being a body that I have used several times in the past.
All told, you can only control what you can control.....no more. Some events are just the result of the material expressing its intolerance of conditions.
Categories: Wood Firing, Down Firing, Dunting, Reduction Cooling, Woodfiring
Tags: Down Firing Wood Firing Woodfiring Dunting Reduction Cooling
Hi Bruce,
Is that a Manabigama you're firing? I'm about to fire my sixth firing in my Manabigama. Each firing has been different. My first one, though was the most even, I think: cone 12/13 up front, 10 towards the back. I seem to be focused at the moment on stacking space, whether to place shelves from wall to wall or leave space on either side.
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Yes, it is.
I have fired one or another over 30 times and have done quite a number of workshops at Monocacy Pottery that help prepare people to do rudimentary wood firings.
The most common way to fire one of these kilns is to pre-heat with propane, build an ember pit under the grate for a couple of hours with kindling sized wood and then, after a couple light stokes, start in earnest until temperature is reached.
As you probably know, this can be done very quickly and, after the passive dampers are removed and the kiln is soaked at peak temperature for a few hours, it is allowed to clear completely and then sealed up until unloading.
Many commercially prepared clay bodies and most shino glazes react pretty well in this environment. Lots of folks find that cone 12+ is necessary in front in order to even the back out to about cone 11. This kind of firing is fine and produces results that can be quite handsome.
The exact same kiln, with a few minor variations in approach, can be fired for much longer periods; producing deeper and more varied ash and flashing effects. One thing that stays constant, unless you can live with a very uneven temperature distribution, is that the shelves should be 12" x 24" and several inches should be open on each side of the setting. Pots can be placed in the resulting "alley."
This is the firing schedule that I have used lately. Keep in mind that I am using a lot of indigenous clays that are minimally processed and so the firing is geared toward them. It is true, though, that several commercial bodies react well to the following schedule. Standard #508 and #380 are my favorites.
First, place a couple half, soft firebrick in the upper flue in order to drive the flame and temperature to the lower rear of the setting.
If they fail to do their job, you can pull them off the flue and into the base of the chimney with a long poker thru the upper passive.
Hours 1-6: Pre-heat kiln without propane and build large ember pit.
Hours 7-12: Slow climb to about cone 08. Try to maintain an oxidizing atmosphere and take lower passives (just the top brick) out at hour 10.
Hours 13-18: Climb to cone 10 down in the front and cone 8 down in the back. I get better flashing in this temperature range. Many high ball clay content bodies do. Alternating reduction and oxidation cycle.
Hours 19-30: Hold at this temperature for a soaking period. This can go on longer if you want to. There is no need for a ton of smoke.....just an alternating, natural reduction and oxidation cycle.......just like in hours 13-18.
Hours 31-36/38: Six to eight hours of down firing. I seal up the kiln thoroughly after the last heavy reduction stoke is cleared. Then I close the damper almost, but not quite, all the way. The idea is to continue stoking (I use either seasoned/soaked or green wood) while there is no draft going through the kiln. If there is, you will get all kinds of spikey ash on your pots and probably won't like them. Therefore, gently place the wood in the kiln until you see flame at the small damper opening. Be gentle. Don't stir up the ash pit.
Wet wood takes a lot of energy to burn and so the temperature drops pretty consistently. A pyromoter helps a lot at this point. You don't want to stoke a lot of dry wood and then realize that you have gained a lot of temperature and probably deposited unmelted ash on your sticky pots. Continue like this til you hit about 1450F. Then close the damper and take a nap.
Be sure to let the kiln clear each time before stoking during cooling or you will lose all reds.......you'll have gray/black pots....which you may like. They can be quite beautiful.
Just experiment and have fun!
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Hi Bruce,
Thanks for sharing this. I finished loading the kiln, and I stacked it pretty tightly. We'll see how it goes.
Is there somewhere you I can see your work online?
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