twsincich

Thank you all for the kind words and support! Been a wonderful adventure so far and am excited to see where the road leads now that I have some bearings! Will keep you all posted on the next firing! 
 

Thank you all for the kind words and support! Been a wonderful adventure so far and am excited to see where the road leads now that I have some bearings! Will keep you all posted on the next firing! 
 

Thank you all for the kind words and support! Been a wonderful adventure so far and am excited to see where the road leads now that I have some bearings! Will keep you all posted on the next firing! 
 

Well done!
Don't be in a hurry. If you burn larger pieces of wood, you won't have to stoke as often and it won't clog up the ash pit. Ideally you should be able to fire without having to scoop out the ash pit much at all, if ever. This type of kiln it not at all efficient, so let it go slowly, take your time, enjoy the process. Remember that you're also heating up all those bricks and shelves, which is a lot of mass. 

More chimney (taller for sure to suck better).
That dampermaybe low as you said 5 bricks up from floor, How tall is that in inches? Low. if it was waist high the flame/heat expands out of the chamber and then gets reduced down and then expands again after the damper The damper that close has little expansion space which will slow draft down a s well. A taller stack may help this flaw.
I cannot tell how much flame expansion space you have?
The double expansion is spelled out well in a few books like Nils Lou  space age kilns.If I recall-its be awhile so I hope i have that right. I biult the double  expansion stack in my salt kiln and its works great with less taller chimneys .I have 7-8 feet brick and 8 feet of heavy stainless pipe
Read up on making cone pack making. Cones should face slightly away from each other so than do not fall on each other for better reading-good temp records count

Good job! Firing a wood kiln is a very grand dance.     Porcelain is quite delicate and wont hold up to that heavy level  of flame impingement like a good grogged stoneware. It seems they were overfired by a few cones!  You might try to use stoneware pieces to act as a bagwall.     The rebar will sag. Even more so if the coals build up and block the inrush of cool air from underneath .    I see you didnt weld them to the tbar so you could just turn them over each firing and get several more out of them.  I pull mine and lay them on a concrete slab and beat them straight with a sledge hammer.
Keep up the good work and let us know about your next firing.

That’s a beautiful piece (kiln) of compact design. I’m delighted you worked through some bugs. The rebar will sag and spall, you’re aware, but the thickness you chose will make it last longer and they’re a consumable. The next hundred firings will really teach you something.. Bravo.

The pieces came out really well, especially since this was only my 4th time firing a kiln and first time slip casting anything! I made a cone 10 stoneware body and a cone 10 porcelain body to cast with and made 16 new cone 10 glazes to test out as well. So I definitely risked all my marbles that I'd be able to get the kiln up to temp! Everything in the very front split apart which I am assuming because it was directly near the burning wood and sometimes the wood did hit the pieces. So that is an easy lesson to fix. I'm thinking maybe some kind of bag wall of bricks would help? Ideally I would probably want the firebox and grate to be much lower to prevent this but without a huge rebuild I'm hoping I can figure something simpler out. Everything behind those fired wonderfully! 
 

 
and some glaze testers 

 

As for the firing itself, I started much earlier than previous firings to give myself plenty of time and options to be patient and learn the kiln. After blowing up so many pieces being in a rush last time I let everything dry for a few days after finishing glazing and let it all candle with a heat lamp in the kiln for another day. Started the fire at 10am and wanted to hold it under 200 deg F for at least 2 hrs to make sure everything was as dry as it was going to get. Then I slowly starting to increase the temp until I hit around 500 deg F and then followed my usual climb rate of about 150 deg every half hour. No particular reason for 150/half hour but my first fire followed that and it seems to work. This was all done by simply using little cedar shake strips burning in the air intakes. After i hit 500 I started to put a piece of my cut 2x3x14" pine pieces onto the fire grate and would used splits pieces of those to stoke the air intakes. This rhythm of putting the full piece on the grate and then using split pieces in the air intakes seemed to work well to regulate the climb and get the wood to burn all the way down efficiently. Once I got to around 1800 deg F I started putting the single pieces onto the grate and there was a sufficient coal bed to burn the wood without stoking the air intakes with split pieces. After about 2000 deg F the climb started to slow down and I started to test different damper, air intake stoke and wood addition ratios. I learned that keeping the air intakes clear and allowing the coal bed to burn down allowed the wood to burn quicker. (I'm assuming because it was hot enough and more air intake) I also realized that instead of using full 2x3x14" pieces, if i split them into 3 or 4 pieces and added them onto the fire grate more often they burned quicker and the temp climbed easily. I was easily able to get to 2394 deg F (but NOT 2400 haha and I used a lot of wood and time to try to get there) At top temp I closed the chimney damper all the way and bricked up the kiln. I am fairly confident I can get it up to temp quicker and more efficiently than this time, with less wood now that I have gotten familiar with the kilns habits. 
 

 

@Kelly in AK @Russ @neilestrick @Biglou13 @C.Banks
 
Hello to all who have posted help, just wanted to give an update since my most recent kiln firing with your suggested modifications. Thank you again SO MUCH for your kind words, advice and encouragement! 
I am happy to report that I believe the firing went very well! I was able to fire the kiln up to a top temperature of 2394 deg F and the cone 10 on my cone packs in the front and back were completely bent. I think I may have even gotten to cone 11 in the very front but do not have cones for 11 so more of a guess. Started the fire at 10am and bricked up the kiln and closed the chimney damper all the way at 12:30 am for a total fire time of 14.5 hrs, which I am very happy with.
What took so long? Well, I thought if I learned slip casting I could fill the kiln up quicker for another firing to test the modifications but of course that took a few months longer that planned. 
The modifications I made were:
1- Enlarged the exit flue to almost double the size it once was. Drilled small holes along the line I wanted to cut and then used progressively larger bits until the block fell right down. Not very pretty but perfectly functional and my major concern was cracking the pieces of brick left, so, success there. 



 
2- Rebuilt the fire grate with 1 1/4" rebar and T bar steel that I picked up from the local junkyard. Little slump in the front (I'll add a support brick in the middle next time) Worked great as a cheap, replaceable fire grate that raised the wood up about 5 inches from where it was last time and opened up the coal pit area under it significantly. I could tell when I was firing that the coals superheated the wood, which burned better and faster and I only cleared out the coal bed minimally this time whereas the previous firings I would have to constantly rake out the coals once I hit 1900 deg F and would end the firing with a large pile of coals on the ground after. 


How many firings will it last? I don't know but easily and cheaply replaceable. 
3- Opened up the air intake space in the kiln door to allow more air in. As the coals seamed to burn down better and faster and the kiln seemed to draw well the entire firing, this seemed to help a lot in connection with the raised fire grate. 

 
4- Insulated the chimney more up to the damper. I didn't have as many soft bricks as I thought so I just used a mix of hard and soft for this firing with some simple fireclay/sand mortar to see if it worked before I did anything more substantial. (I have to drive 3 hours to Portland for firebricks/clay/most things I need) Seemed to help! There was always a strong pull in the kiln and flames shooting up when I would stoke. 

Thank you so much for your kind words @Kelly in AK! Everyone here has been incredible so far. 
 
I agree, I wish I’d made my firebox bigger. Bigger cross section and space under the grate. Luckily It sounds like I have some options and I could still drop the floor down if it’s still not enough. That way the air is coming in low enough to heat up before reaching the wood like you suggested. 
 
My first thoughts before starting anything was, the smaller the better. Cheaper to build, Fire, easier, etc etc. The main thing I’ve learned during this whole process is bigger is always better! You can always brick in a flue, make a bag wall if the kiln is half empty cause there’s too much space, would be easier to load if I could fit in, and with a wood fired kiln the firebox is probably never too big. 
 
I love your idea about double bricking the chimney! It’s really only doubled up the first brick and a half, would be easy to go up to the damper that’s 8” above the top of the kiln. Does that sound like enough, at least to start? Would you suggest hard brick or soft brick? I was told soft brick insulates better and wouldn’t be an issue since it’s outside of the kiln atmosphere? I mortared the chimney bricks with high fire alumina mortar up to the damper so nothing would seep out. But I have some extra bricks of both hard and soft. 
 
I was reading about the groundhog kilns in the Carolinas and loved those! They sound great. I grew up in Florida, wish I’d known about them then!
 

Another though- this kiln design is not really made to fire fast. The only reason it might fire fast is because it's small. It's a mini anagama, and anagama are not efficient, fast firing kilns. That said, even large anagama can get to cone 10 much faster than people typically fire them. A kiln that is fired for 3 days can get to temp in less than a day no problem, but they are fired that long in order to build up ash, giving the surface effects that are desired from this type of kiln. But still, 18 hours is a lot slower than 8 hours. So take your time and don't rush it. Let it soak, as we say. Anagama have a very small ash pit to firebox ratio, so the ash pit will fill up quickly if you try to fire too fast. Also, small pieces of wood burn quickly and produce heat quickly, but they also produce ash quickly so they're not great. You can quickly fill up the ash pit and then your air flow drops. Once you open up the flue and intake, I would definitely try firing with larger pieces of wood, like fireplace size logs, even if you can only fit a couple at a time. The little stuff is fine for early in the firing, but you need to get to bigger logs as soon as you can.
Are you using a pyrometer to time your stokes?

Im going to say no, its not too small. With adjustments you should be able to get it to c14! The flames off the wood are hotter than that.  You just have to release the btu's stored up in that wood quickly with enough oxygen to burn it.

More air, more air and more air. If you can force air into the firebox and have that part adjustable  (a motorized fan of some sort with a speed controler) you can overcome alot of the"issues" youre having with undersized intake, exit and chimney size. My suggestion is to do as you proposed...enlarge your exit flue, enlarge the ashpit and forget about the chimney... with forced air chimney height becomes a non issue.  Adding more exterior insulation also helps alot.  When i first built my kiln i had some of the very same problems. It would take 12 to 16+ hours to fire. Ive now got it down to 5hrs +or- to c10 in the coolest parts which for me is the lower back portion .  When the blower was added to force air it cut the time down to 8 or 9 hrs.  Since then Ive changed stacking configuration leaving room for the flame to pass thru more readily along with a few more tweeks to get it to a consistent five hours. And its several times larger than yours at eighty cubic feet stackable space. Tons of wares, shelves and furniture along with the hardbrick mass to heat up.  So keep firing and tweeking things around. Dont worry about making mistakes... its how we learn!

Pieces from the Second Firing
 

Yes. It should be close to intake. Its very hard to make it bigger while firing . The damper will control the size IF its made larger than needed.
Yes also. You need lots of room under the grates for the coals and to also keep the grates from melting IF youre using metal grates. I try to not let the coals build up more than half of the space below the grates. It will choke off the incoming air and cause stall.  .....wood kilns need LOTS of air to fire correctly.
Adding air with a blower of some sort will cut firing time in half or more and will increase temp IF you make sure youre not under feeding the fire. Overfeeding will also affect but not nearly as much. Watch the chimney exhaust. .. a little smoke at stoke is ok and then see it clear within several seconds is good. Smoke all the time thru firing.. no good. Too much fuel.
Also your wood size is what Id use at the beginning of a firing till about bisque temp. After that its smaller stuff with way more surface area for burning. Take one of your 2x3 pieces and split into 4 pieces. Itll burn way faster and release more btu's quickly.
 

I followed the 10:1 rule from Olsen (firebox : flue size) on a similliar project and found I did not get enough pull with a 9 foot chimney of 81 inches in area. I came to the same conclusion that the exit flue is too small. I liked the idea of a fast fire kiln but in my case there were other issues with the depth of my firebox in relation to the heigth of the kiln.
I haven't got back to it but I'll rebuild with twice the flue size and look more closely to a ground hog deisgn with a low, wide chimney instead of the tall, narrow fast fire design.
Established kilns I've been a part of have run into heat saturation issues atfer too many hours of struggling with what amounted to overloading. I bring this up in repsonse to @Biglou13 as I'm sinscerely curious if your design has the mass to succeed as anything other than a fast fire. I don't mean this as a criticism I only mean to work out what expectations we should have from kilns with less mass.

How thick is your floor?   How tall is your chimney?  
 
I need to study post more but first idea is  taller chimney. 
 
sometimes you have to ride out the stall with more time.   

@twsincich Welcome to the forum. It's really difficult to fix this without seeing it, as there are at about a dozen variables at play here, but based on your numbers, your ash pit it probably too small, as is the flue opening, as is the air intake. But it may not be. It may be that you're just letting all the heat out the chimney and everything else is fine. You may just be stoking too heavily or too lightly. But based on the fact that it does better with a fan, and that you have to leave the flue wide open, the air seems to be the problem. Like any fuel burning kiln (gas, oil, wood, coal, or whatever), you have 3 factors to deal with during the firing- fuel, air intake, and damper. They all work in unison, and adjustments to any one of them will require adjustments to the other 2 to get the rate of climb and atmosphere you want. You're maxed out with the damper, so the other 2 are limited.
Is that base solid concrete? Is the floor of the kiln directly on the concrete? How thick is the floor of the kiln, and what material is it?