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Kristin_Gail

First Firing Of This Here Electric-To-Propane/wood/soda Converted Kiln

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Oh my, all the help I received here in the planning, purchasing, moving, building, firing of this thing!  Am I ever thankful for this place.

 

Thought I'd share just a bit here.  Details are on my blathering blog.

 

This is Big Anthony.  I think his chimney is too big.  But he works just fine.

 

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I'm single-firing, and the process took about 21 hours, freezing cold to Cone Six.

 

He stalled at about 1950°F, and I fired the rest of the way with the addition of wood - which I'd planned to do, anyhow, for fun.  Just didn't realize I'd have to do it.

 

Learning is a process, right?  I completely screwed up the reduction I was hoping for; I only had four soda ports, located between the firebox and the shelves, and didn't get all of my soda introduced (near the end, the metal wand from the garden sprayer shot out of the sprayer, laying squarely in the firebox); and I accidentally crash-cooled it.  But I still got some great teaching results, considering this was the first time I'd ever fired any non-electric kiln beyond a couple test propane/soda kilns.

 

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I learned a lot - ohmyword, so much - from this firing.  So much about firing this kiln, and firing kilns in general, about slips and glazes, placement of pots in the kiln, what my brain can and cannot compute on no sleep ...

 

In any event, it worked!  I'm forever thankful for all the help I received here.  It worked!

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The interior of the kiln - soft brick sides/floor and fiber ceiling - were sprayed with EPK/Alumina Hydrate (50/50). My ITC had gone bad after 7 years in storage. I figure the fiber will only last a handful of fiings, maybe a year or two for the bricks. We'll see. If the ceiling does go fairly soon, it will give me an excuse to replace it and, in the process, make it front-loading!

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I like the mug in the last pic with the residual soda. I am worried about those burner mounts. Will they be beefy enough to last?

Looks like fun.

TJR.

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I to like your last mug in photo and 100% agree that to big is fine just as Neil said close it down at exit flue-when you find the right spot it should help speed up the firing as well as working better-wheres the damper?

Mark

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Thanks so much for the encouragement, folks. I am certainly having gobs of fun.

 

TJR, I can't tell if you're kidding? You mean my angle-iron Erector Set doesn't look stable to you? It will eventually be bolted to the concrete slab - holes are drilled in the slab; we're just waitingfor warmer weather for the epoxy to set properly. It was still pretty solid, just sitting there.

 

I had intended to put half a brick in the exit flue, but had forgotten. Think this might help with the stalling? I really didn't mind it, though - it gave me a great excuse to use more wood.

 

The top of that last mug is not pretty: http://kgspottery.com/MessesMostly/January_2014/11.jpg Liner glaze went on before exterior slip. Oops. But I was so happy with that orange flashing!

 

Mark C., I put the damper in the chimney, just one course above the exit flue: http://kgspottery.com/MessesMostly/BigAnthony/41.jpg Hopefully that makes sense. I did leave a one-brick clean-out thingie at the base, directly across from the damper, as someone here suggested. I've been very thankful for it! We had to build a fire in the chimney first in order to heat up the chimney and create a draw for the pilot burner.

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A fair amount of the mugs have cracks in the body, radiating out from where the handle attaches on the bottom. (http://kgspottery.com/MessesMostly/January_2014/18.jpg) I've never experienced cracks in wares before - so I don't know anything about it. I'm assuming it's a matter of clay body and single-firing, possibly going too fast during a particular stage? I'll mess around with that, but thought I'd throw it out there in case someone had an idea.

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The cracks are possibly dunting from crash cooling, or from going up too fast, or.......Lots of variable at work here.

 

Getting the flue exit downsized will help with getting it to reduce, too. When I reduce gas or wood kilns, I choke it down till it stops climbing in temperature, and hold it in reduction it for about 45 minutes.

 

The burner rack looks fine to me.

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Was the ware really dry when you loaded the kiln from the green glazing process?  If not and it was well below freezing....... and it sat there for a good while before you fired...... that coud be the cuplrit in some or all of the cracking.

 

Look carefully at the cracks.  If the crack is THROUGH the glass layer on the surface very sharply Ilike a crazing line), the cracks happened on the cooling cycle (exacerbated by a too big chimney,.... if what you did was to forget to close the damper ;) ).  If the cracks in the glass have seeped into the cracks or are pulled away at the edges of the crack a tad and rounded off... the cracks happened before the glazes fused otr the soda went in.

 

best,

 

................john

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I think John and Neil have hit it as to cooling to fast. 

1st that was my suggestion on the extra chimney  brick hole and your stack looks great by the way-you just need to add a brick inside in flue to choke it down a little. Also does your damper seal the bottom slot well in  stack? Meaning is it the right size to cover the slot hole ?

Did you put the damper in when you turned off kiln? and fill the burner holes? and slow cool this kiln or something else?

You want to keep cold air from getting pulled and having the stack pull it through when fire is over. So whatever you can do to stop this is whats needed.

Thats what I want to know.

Mark

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With soda and salt firing, the rate of cooling can have a great deal of impact on the final color of the pots. I used to use a pretty light colored stoneware clay in the salt kiln, and if I closed the damper tight at the end of the firing I could get it to come out a deep chocolate brown, much much darker than it ever appeared in a regular gas firing. The faster I cooled the salt kiln the lighter the color would get. Generally I would leave the damper open about 1 inch to get the medium brown I liked. So experiment with that. You'll also notice a difference with your flashing surfaces.

 

Mark makes a good point about the damper. If there's a gap above the damper shelf it can undermine the draw of the chimney. The gap effectively becomes a passive damper, where the chimney will draw air before pulling from the kiln. So make sure there's a pretty good seal around the damper shelf. You can always just put bricks on top of the shelf to block the gap if that's the case, or weld a piece of angle iron across it. This will give you the best control during the firing and cooling. If, with the damper closed completely, you still find it's cooling too quickly, then cover the burner ports too. Generally if the damper seals well you won't need to seal the ports.

Kristin_Gail likes this

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Well.  It's embarrassing.  But I am unfortunately not a person who functions - at all - without sleep.  Therefore, when it came time to cool at hour 22, I left the damper where it was (don't have my notes here but it was probably 1" open) and turned off both burners, left just the pilot on.  I was truly hoping to fire down, taking many hours.  I sat there watching the temp fall at hundreds of degrees per second (exaggeration, but only slightly) but couldn't get the information into my brain.  I just stood there and stared.  It was all a fog of dizzy numbers.  I think after half an hour and hundreds of degrees, I finally figured out I should at least plug the other burner port.  It wasn't until I turned everything off, buttoned it up, and sat down inside for a moment that I woke up and understood just how badly I'd messed up the cool-down. 

 

I still hope to fire down next time, but with a real burner.  Or both, if I need to.  Crikey, at the very least I could just turn everything off and plug the entire thing up, safe and snug.  What I did is just bizarre.  (When short on sleep due to new motherhood, I often forbade myself from driving, my brain is so incapable of functioning in this state.  Anyway...)

 

And you're absolutely right about my damper.  When we built it, I knew the space left (I think it's less than 1/2") would need to be plugged during firing - but forgot.

 

I'm thinking next time (this is sort of at the recommendation of Marc Ward) to fire it through the very slow temps (700) one day, then button it up and sleep. Come back the next day to take it to temp.  A sort-of bisque.  

 

John (did you get my thank-you e-mail?), these pieces were very dry.  But they had indeed frozen twice - once in the studio when it accidentally froze, and then overnight in the kiln.  I'll examine them more closely.  But it sure does sound like the crazy crash cool is a safe guess.

 

I know I did so, so many things wrong - the cooling being the biggest, I think.  But I really can't believe how much this one firing has taught me.  Still fairly amazed at it all.

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All and all ceramics is a constant learning curve-By the looks of the shed and kiln I would say you did a GREAT job. 

Next time write all these details down so when you are burring the angle at both ends you have a focus as its written down.

Things to avoid are freezing pots -just do not let that happen

and close up the kiln tight when done.( I'm not a firing down guy with my salt or reduction kiln.)

I cannot tell you the amount of times I double check my damper after a fire to make sure I closed it. even with 30 plus firing every year I always check it at least twice.

You did a great job on this kiln repurposing feel proud.

and welcome to the kiln zombie world.

Mark

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If it is stalling, check your draft. Light a newspaper torch and hold it at the connection between the flu and chimney. The flame should be drawn into the stack. You can also test it by closing all the openings except the damper..open wide. Hold a torch by the burner port and see how string the draw is. I helped fire a wood kiln (fast freddie) in Banff and it kept stalling at 1900. Les manning called up Fred Olsen for advice. He said the stack needed more height. Banff is at 6000 ft above sea level. I don't know your altitude, but if you are at a high altitude, you may need to add some height to your stack. In Montana at 3000 ft. I needed more height for venturi burners. The stack was 25' for 60 cu. ft. car kiln.

 

Marcia

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Well. It's embarrassing. But I am unfortunately not a person who functions - at all - without sleep. Therefore, when it came time to cool at hour 22, I left the damper where it was (don't have my notes here but it was probably 1" open) and turned off both burners, left just the pilot on.

That's exactly why I said what I said above.... I've seen that mistake happen with new fuel-kiln firers a gazillion times. Youe are NOT alone.

 

Like Neil, I used to fire salt a lot... and to get good greys rather than browns... I always crash cooled the kiln deliberately. Works a bit with soda also.

 

best,

 

.....................john

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You know, I came here to offer gratitude with a little report. I had no idea I'd find even more answers and so very much encouragement.

 

I have visited so many wood or soda or salt potters who explain they have to have an entirely different "line" of electric-fired ceramics to sell at shops, and keep their main pieces to sell on their at their studios (where they can explain the process in person) or perhaps a fine gallery. I'm now experiencing it first-hand, even at these very early stages, and it isn't very fun, eh? Even friends who collect pottery have no idea what to say except to nod and say, "Um, I like the orange ..." As my throwing and firing improves, I'll feel more confident to explain to friends, "No, really. This isn't a mistake - I want it to look like this!" But for now I'm truly thankful for you folks. You're my one and only cheering section.

 

Mark C, I just saw your comment - thank you so much for telling me about the clean-out hole. Very necessary!

 

Marcia, I'm pretty much right at sea level - 230 feet, Wikipedia tells me. If I don't find answers with the brick in the flue and plugging the space above the damper, I'll think about chimney height, too.

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