First Firing of My Homemade Kiln
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- čas přidán 23. 03. 2021
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I built this little convection kiln a couple of weeks ago and now it is ready for the first firing. My friend Matts Myhrman came over and helped me fire my homemade kiln for the first time. I fired my culinary shoe pot that I had made recently and learned a bit about how best to fire my kiln.
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A few folks have already mentioned rocket stoves - also worth noting that this design is a bit more like a “masonry heater.” Efficient and clean rocket stoves use an *insulated* “heat riser” AKA “chimney” or “secondary burn chamber” - the insulation allows a faster rise to your target temps and more quickly enables “secondary burn” in which your fire is hot enough to burn the smoke- creating even more heat more efficiently. An uninsulated heat riser will take FAR longer to get up to secondary burn because all that masonry is acting as a heat sink & thermal battery: wicking away your heat until the thermal battery is “charged” (and can then give that heat back to your kiln shelf and clay bodies.) Non-insulative walls is why your temps hung for so long in the 500-600 range before eventually climbing higher. That period of stall is your brick mass absorbing heat. …So, 3 recommendations from the rocket stove / masonry heater world:
1) insulate your heat riser. Ceramic fiber or insulating refractory fire brick work best… but are expensive. You can make DIY insulation with clay, sand, and perlite for super cheap. Perlite can be had at your local garden supply.
2) make your heat riser both *taller* and *sloped*. The ancient Chinese pioneered the use of “dragon kilns” needed to make high-fire porcelain, and were built along slopes instead of direct-updraft kilns like the British “bottle-kiln” designs. Direct updraft wastes most of your fire’s heat directly up your heat-riser/out your chimney. A sloped design will radiate more heat back toward your clay bodies…and that’s one reason why the Brits couldn’t replicate fine porcelain china for so many centuries.
3) add “over-fire” air channels to introduce **pre-heated** secondary air. Adding a few more small holes at the level of the top of your firebox will give the fire’s pyrolized woodgas (“smoke”) more preheated oxygen right when & where it needs it - in order to create the much hotter, cleaner, and fuel-efficient burn to boost your kiln temps. The “solo stove” campfire rings work on this secondary air principle, too - take a look at their simple design to see the level at which they introduce heated secondary air.
All great tips. However part of the point here is to offer a kiln design that is easy and cheap to construct. Insulation adds a level of complexity. I do like the simple, efficient design of the Solo Stove, this link shows how that works blog.solostove.com/how-to-secondary-burn/
Thanks for all the thoughtful and intelligent feedback. I will be thinking about how to best incorporate these ideas in my next kiln updates.
😂 you stole my lines. I was going to say the same thing about a longer tunnel that slopes upward. The Chinese kilns were actually built on a hillside with a gentle slope
You may have already found out but you could easily turn that into more of a rocket stove and get hotter, cleaner, faster. Just add a shelf for you fuel that goes in maybe a third of the way inside and put your fuel on that. The clear space below the shelf will draft in air under the fuel.
Yes, thanks. That was actually one of the first modifications I made to this kiln.
What would be ideal for the fuel shelf? Another grill like what is used for the pottery? And would the pottery shelf then need to be moved up higher? Thank you! Taking so many notes as we prepare to build ours! 😄
use the kiln to make charcol and then use the charcol to fuel the kiln. charcol burns hotter than wood because it has less water in it
That's a good tip, I'll be it would get a lot hotter using charcoal.
You have inspired me to make ceramics
Thanks I am glad to help inspire you.
same!
Maybe a deeper stack and longer firebox will benefit temperature control. Using rocket stove basis!
Yes, I think that makes sense.
Hey, maybe you should try doing mexican prehispanic pottery from aztecs ando mayans.
I would be cool with that.
i just test fired my kiln as well, had a lot of fun
Great!
That's a real furnace!
Bet the neighbors aren't thrilled about the smoke! 🤣
This first firing was extremely smokey, but since then I have figured it out and it isn't that way anymore.
the IR sensor in your temp gun reads everything it can see. If you look at the openeing the sensor is in, you will see that it is cone shaped. The sensor sees everything within that cone. The fartther you are from your target the larger the area being read. If you want an accurate reading of a small area, the closer you get the better.
Well now I'm going to have to build a kiln this spring!
We have been doing trash can firing successfully with many drilled holes in the sides to bring in air. It creates great smokey streaks on the pieces. I found a small burn barrel which should work even better. I have collected many old kilns for the brick and hope to build with these soft bricks as liners.
Also, thanks for the tip on damp areas. Subscribed in damp Vermont.
Sounds great. Thanks.
If you igloo up the bricks on top it will draw much better up don’t even have to mud them. Leaving a 5 inch hole on top
Good tip Tony. I will pick up a few more bricks and try this.
Hi Andy, great results! We can't wait to see how you seal the pot. As you mentioned, elevating the fuel to scoop out the ash and level out the coals will definitely add some heat.
Thanks for the tip. Ever onward!
Great to see....nice ring to that pot.....thank you.
Thanks for watching!
Thank you
Love your channel! When I fired a wood fired Raku kiln at college we used Pine? Pallet wood which we split length ways about thumb thickness so it would burn hot and fast.. At the end we were literally hardly able to post the wood in quick enough... But we were firing Raku heavily grogged commercial clay... I think the larger branch bits you used were good for a slow start... Whish I lived nearer to come and try 😁 Somerset UK
Thanks for giving your experience. Greetings from across the pond!
Wooow i will definitely fire with the pine nuts to try to get black pottery. Thank you so much for the ideas. Amazing results.
You are welcome. Thanks for watching.
Very nice, thank you for presentation. Best regards from Saxony.
Thank you so much.
You have great music taste, I love this channel!
Thank you very much!
Beautiful video! Love the music too😁the shoe came out fantastic and I hope you can make delicious meals in it! I tried to make on but it turned out to be a planter😊loved the process anyway, wish I had the space to build me a kiln like that, (my smoked fire pottery was done in a galvanized trash can) also too many restrictions in the LA area, it is my favorite style though. Thank you again for sharing your well of knowledge and continue to
learn with all of us clay lovers🙏🏻💐🕊
Thanks for watching and the encouraging words.
Great work. It should be interesting to see how you are going seal this pot. Thanks.
Thank you.
Nice experiment. You might try basic charcoal if just looking at achieving predictable temps for testing.
I have been thinking about trying charcoal actually. Thanks for the tip.
Tony Soares uses it to great success.
I'm curious to see how you seal this pot. Great work!
You and me both! Thanks
Interesting video and I plan to build something similar when the project reaches the top of the todo list. One comment I would make is that the fuel must make a significant difference when it comes to performance and when I first saw your small basket of scrappy looking Mesquite wood I thought you stood little chance of success. We don't have that wood here in the UK but much to my surprise I now read it is high in lignin and burns quite hot. It would be interesting to learn more about which woods have high calorific values and for us here in the (damp) UK a wood moisture meter would be essential and are cheap and easily available online. Totally agree about your Mkii version to keep firebox above the spent ash and suggest that Mkiii should incorporate some kind of forced air flow such as bellows or something along those lines - blacksmiths use them when working with molten metal and they must require temps much higher than we need. Anyway, a very pleasant way to start the day and thanks for taking the time to video your efforts and make it available to all :) Paul
Thanks for your feedback and suggestions. Keep your wood dry, it makes a huge difference. Also popular for firing here in the American Southwest is Juniper wood.
Good show Andy , I like it better the more I see for my area, looked like mica clay.? Should help it hold water .. nice
Thanks. There is some mica in my clay from the local mountains, but not a whole lot of it, just enough to add a little glitter to the pot.
A concentrated airflow like a blow dryer in a steel pipe will help. The fan works like blowing into a bottle, not all of the air goes in. An old blow dryer will give you those quick temps that you are looking for without the 100 degree drop.
Thanks for the tip!
@@AncientPottery thank you for posting the construction. I've been wrestling with the idea and materials, I was thinking brick and cob and I like your idea. I got the blow dryer ideas from the King of Randoms channel for a Foundry to melt aluminum cans. He uses the blow dryer and charcoal to get up to temp to melt the cans. The steel pipe is built into the design.
@@AncientPottery This is the setup in action. czcams.com/video/lSoWxG30rb0/video.html
I've been looking for something like that
I love your work and videos.
Chimneys seem to be an integral part of a kiln, so much so , that there are formulas for firebox to chimney ratios.
Perhaps, a metal pipe or some sort of improvised chimney would help get your temperatures up, if that's what you want.
Cheers.
Thank you. Yes, I have had a number of comments on chimneys and draw, I am going to try something with that next time.
I think it needs to be clayed all around it, the entire kiln. out side, to cover the gap where air comes out and doesn't allow it to burn hotter
It's pretty airtight except for the holes I allowed for oxygen to enter. Check out my most recent video where I fired mugs in this kiln, I added a chimney at the top and that seemed to help a lot.
Could you make a video showing how you add the grate to the bottom for the ash? /Are you sliding more grates in?
Yes, when I make this change to the kiln I will record a video showing the process. Thanks for the suggestion.
To raise temps, try using smaller strips of wood. Sometimes they are available as waste from mfg places. (Learned from Lenca wood fired kilns in Honduras)
Well done on your test fire👍
Thanks and thanks for the tip.
Seems like you got to cone 011-012 based on the Orion cone chart! Great first firing!
Thanks for the info, I don't speak "cone".
@@AncientPottery there are charts on the internet that show what temperature is rated for different cones typically it's used for electric kilns because the different cones will melt or bend over at different temperatures. If I was trying to kiln low fire bought clay at a low cone value in a home built kiln like yours, I can see what temperature it should be able to be cured at and using the thermocouple I can match the temperature of the kiln to the clay.
Nice video with some great knowledge to it but I would suggest to make you a longer Firebox with an arrow opening on it it will cause a better draft through it
Thanks for the tip
Hi uncle andy I miss you and love you so much and it's me melody on my dad's youtube love you
Hi Melody, you look like Melvin in your picture. I love you sweetie.
I like the design Andy, nice job. Having the grate for the wood helped a lot in my kiln which has a similar setup. I also would really like to find a good way to seal pots like this (earthenware flower vases in my case). So far I have tried: tung oil, sodium silicate, polyurethane wood sealant, clear Krylon spray acrylic, terra sigillata, and fastidious burnishing, none of which have been a resounding success yet... I can juuust brush cone 06, so I might have to resort to glazing.
Thanks! I am not looking for 100% sealing, just to slow the seepage. I think either glazing or coating with something like tar might be the only ways to seal completely.
@@AncientPottery I have run into an obvious-in-hindsight problem with trying to seal my woodfired pots in an electric kiln: The bisque from the wood held great, I used cone 06 glazes to keep the temp below the melt point of my harvested clay - and lost all the beautiful fire marks on my pots from the fire. They hold water like a champ - and turned into lovely plain terra cotta pots. Live and learn. If the bisque ( 06) temps can burn off a pencil line they can also burn off smoke patterns!
Cement + foam (detergent bubbles) = cement foam. Good thermal isolation. Cheap. I wonder if putting some on the bottom and on the floor would increase Temp. Good video. Thanks.
It seems to me that this could help some. Although most heat is obviously going out the top.
You could also insulate from the outside using the Clay/Sharp Sand and Straw. 👍🙋♀️🌈🌞
Yes, I suppose that would help. Thanks.
Where did you get that thermocouple setup, I like that analogy gauge
Like this? www.theceramicshop.com/product/19222/pyrometer-analogue-no-tc/?gclid=CjwKCAjwquWVBhBrEiwAt1Kmwj63YVMIx0X9s25Dus8-Njvm8TRJHUewqP0TibFmIayE4_JO9QLzHxoCezUQAvD_BwE
What about putting a flat brick, or stone on the grate, would that help in not turning it black on the bottom? Or help it not warp?
if you build another one, try to raise where your fire bucket it so you can put a hole below it, that way it will suck in air from bottom opening to feed the fire.
Yeah you’ve got the right idea to put in another grate for the wood to burn on, that will increase combustion rate and heat. Curious, why do you think the rim cracked, was it too fast a heat rise, weakness in the pottery or something else?
This was a crack that appeared while the pot was drying, then I fixed it, or so I thought, only to have it reappear after firing. So probably just a stress crack that was formed while drying and was never fully healed.
The taller the chimney, the better the draw. You wouldn't need a fan and the flame is more controlled in an upward direction.
Try some cone 5 6 pottery clay in your kiln and see if you can get vitrification of it.
I don't use commercial clay and I am not trying to vitrify because I am making earthenware.
Omg I 💚 you ...great channel
Thank you so much!!
Do you have to have a grate for the pottery? Why not a flat metal plate that leaves a couple of inches gap around the edge so you are choking the airflow but it could also trap heat better?
Just a thought.
Might be worth experimenting with. All the example kilns I have looked at or seen pictures of had a grate or at least a more porous structure.
Hi Andy, I'm from Argentina. Could you post the dimensions of the oven. Your videos and perfon are very good for my English. Thank you
Sorry for the delay. They are 16 inches wide at the top and 32 inches high.
Thanks....The day after seeing your video I designed my own updraft kiln with 8 inch concrete blocks ...nearly finished...Is the fire box necessary?
In my previous kiln I did not have the long fire box but I felt that I needed it to add more fuel and longer sticks. Watch the video to see how that worked czcams.com/video/XjpxfkSBPgo/video.html
Another great video Andy. Do you think a simple brick kiln like yours would work with an LPG or propane burner as fuel source ? I’m just thinking it would be smoke free which will upset the neighbours less. Thanks.
Yes, I'm sure it could easily be rigged up to work with gas. My latest firing was almost entirely smoke free, the video will be out in a couple weeks on that.
Based on rocket heater technology (or what I know about it), as you said, if you raise the fuel, you’ll get air underneath, cleaner burn, potentially higher temps.
Great, thanks for the feedback.
Maybe charcoal could help a bit.....also you wired the rebar grate together.....was that special? There are wires that can take the heat....great video.
Yes, I have thought about trying charcoal. The wire is just plain old baling wire, it was used because it was easier and cheaper than welding.
If you get to 1200°C do you still need to seal it after?
I want to build a kiln. I live in Michigan. What would you suggest for taking care of it during the winter months to protect it from the elements?
The mud mortar I used in my kiln may not survive long in a wet environment such as Michigan. My mortar is fired into ceramic on the inside of the kiln but is washing away on the outside. Perhaps you might want to use refractory mortar, or be very careful about protecting your kiln from the rain and snow. Maybe covering with a tarp or a sheet or tin when not in use.
hey mr. ward! i know this is an old video, but can you do glaze firings in this kiln if i were to make one? and how long would i have to hold the 750-900 C temperature for the first firing?
I think you may be able to glaze in a kiln like this. No holding temperature is required, just reach the target temperature and then allow it to cool after that. Have fun.
What about restricting the output more? Lots of heat escaping top. Of course you have to accommodate your arm length, but would "firing area" get hotter if you made the kiln a row or two taller? Might be interesting to see where temps go if height is increase by just ONE row of bricks.
Nice video! At around 12:00 you mention the black spots on the clay and I think the blackend spots actually looks nice. If I wanted to fire some ceramic art, what would you recommend in doing to keep the whole surface of the ceramic black when firing until the end, to where the outside stays "carbon-ized with the carbon?
You should check out how the Pueblo potters of New Mexico fire their black ware pottery. czcams.com/video/1zrTO1KYhQs/video.html
They smother the hot pottery with horse manure to infuse the clay with carbon deposits.
@@AncientPottery Wow! Thanks for the reply and video!
Thats reduction firing👍👍
Would it help increase the heat by plugging off the feeding hole at one point of the process?
Maybe
This reminds me of the stone ovens used for baking back in the 18th and 19th centuries.
taco bell bag for tinder can never go wrong
Would it work to place a grate inside with an ash pan underneath? The draft under the grate should increase the heat. Also afterwards the coals that collect in the ashes can be covered with ash and used to fire up and increase the heat for the next time. I used to have a solid fuel iron stove and would leave the grate door open at the bottom so that the draft would fire up the wood quicker, then close it once it was lit. Then at night I would bank the fire. The next day I would rattle off the ashes, blow on the coals, and throw on some new wood and with the help of the draft from the open grate door, the fire would light up quickly. I'm not sure if your kiln would benefit from this or not to create extra heat.
This might work. Can you share any images or videos of what this looks like?
Can you cook in a pot like that on a propane stove, or household stovetop?
It depends on the pot, generally yes, but different clay bodies are better than others.
Would something like this work for entry level. My daughter, she is 10, went a pottery camp for the summer and wants to keep doing it.
Yes, it could, of course I wouldn't recommend a 10 year old firing one of these without adult supervision.
Really brilliant video Andy. How long roughly did it take from beginning to end of firing?
Hmm, not sure, I probably should have paid better attention. I would estimate maybe an hour and a half total.
@@AncientPottery It's easy to lose track of time when having fun! I'm going to attempt a small firing this evening
Could be that the stuffing of wood also made a "rocket" affect with the air coming in? Smaller opening makes the air rush in faster I think:))
Yes, the kiln needs more "draw" I did solve this in later videos.
@@AncientPottery
Oh goody:)) gotta check that out then:::
@@Nilafila76 check out this one czcams.com/video/4z3x8psUUbE/video.html
I'm new here. What is a shoe pot, and why is that design beneficial? I googled it, and got really random things from shoe flower pots to how to recycle footwear. I'm going to poke around on your channel and see if I can find an answer!
czcams.com/video/JoWIz-NgGww/video.html
@@AncientPottery yes! I found it last night! You're so inspiring. And here in Missouri, there is a lot of clay in the soil, so I'm thinking now I need to watch your videos on finding and using wild clay.
Hello Andy,
I keep having difficulty with black soot stains on my pottery. I noticed you mentioned it might be the fuel that’s used. What kind of wood do you recommend? Or maybe it has something to do with the temperature? Maybe not high enough to burn off the carbon? I’m very curious about you advice…
Avoid any wood that burns with black smoke, use one that burns with white smoke. Probably though your problem is related to not hot enough or not good air circulation. You will need to get to about 700 C to effectively burn off that carbon.
@@AncientPottery Thanks! that's really helpful!
I have a few questions if possible Mr. Andy: HOW do you place the manifacture into the "klin" when it reaches such high temperature? I saw a previous video and you used charcoal, why is now better/more useful to turn into wood scraps? and last but not least, are you sure nobody is going to call fire dept.? 😁 my neighbours would kill me for less than this 😅 - Scientificly this is a super content, thank you!
The pottery is placed in the kiln before I start the fire, while the kiln is cold. The charcoal was not used in the kiln, but I suppose it might work, the wood is cheaper and is recycling. Nobody has called the fire department on me yet. Thanks
Nice video. I wonder if you can get the 1300 celcius to make glazed pottery with this kind of kilt.
It certainly would be fun to try to get that hot. On my next firing I will see just how hot I can get it.
* to increase temperature you will need air flow under the coals
how have a ceramic finish
Infrared thermometers only read the air directly in front of it
Incorrect
Very nice. Apparently it took awhile for the kiln to heat up.
Yes, it definitely did. Thanks.
It's almost a year since you made this. Have you used it much? How is it working for you?
Loving it, and regularly reaching temps like 850 C which is plenty hot for my clay. Check out this video czcams.com/video/4z3x8psUUbE/video.html
Great video Andy. Looking forward to seeing more. Do you think using hardwood wood help the kiln burn hotter on your next fire?
Yes, the type of wood can make a huge difference. I have been using old pallet wood recently and that is working okay. Check out the firing in this video czcams.com/video/4z3x8psUUbE/video.html
Did you make those bricks sitting off to the side @9:44?
Those are concrete landscape blocks, so no.
@@AncientPottery
Oh OK I guess I thought they looked kinda handmade. Could be that they are simply worn a bit, or it could be I just didn't look good enough :))
Hi there, you might like to try shaping the top of your brick kiln like a Gnomes hat, with the point chopped off... as they are made here in the UK in the last century and way before. You can find pictures of these when you would Google thus:
The Potteries in Stoke on Trent UK. 👍🙋♀️🌈🌞
Yes great suggestion, you are actually not the first person to tell me that. I am going to try it.
What type of clay did you use to build your kiln
I don't know what "type" it was. Just some clay I dug from the side of the road near benson, Arizona. Probably a lacustrine clay but I don't know more than that.
Are we only supposed to go over 100°
I'm getting my bricks today. Craigslist always has them free
Awesome, that's a great tip for doing it cheaply.
How long do you leave it firing at the highest temperature?
I don't leave it at that temp for any set amount of time. I just reach the target temp and then start the cool down. It's all very quick.
Great job! What are the dimensions of your kiln?😊🐝❤
26” diameter and 31” tall.
@@AncientPottery Thank you so much!😊🐝❤
3:31 hey... that's Steve's crazy neighbour!?
Who, me or my friend Matts? Not sure
Was the wood totally surrounding the pot or only in the fire basket?
The wood goes below the pottery in the fire-box, the pots are held above the fuel on a BBQ grill.
@@AncientPottery Thanks. I missed that. Do you now prefer the igloo approach, rather than your other oven? Creating a stronger directional draft?
@@SharleneJT I have not yet formed an opinion or preference, just trying different things to see what is best.
👌🏻
How do you get your clay?
I dig it from the desert
Is it good to have a little black sand in my clay or should I totally filter that out?
I don't know if it is "good", but it certainly can't hurt anything.
@@AncientPottery I appreciate the education and your response. Thank you bud! 🙏
Your giving me ideas. I have an old large electric kiln I turned into propane updraft. I don’t use it anymore since I made a downdraft kiln. Might build a fire box in front of it and do some wood firing ! Thanks for all your cool videos. Btw I live in the mimbres valley 😎
Good idea, and it is probably insulated better than my bricks.
would charcoal make a hotter fire
What cone is your clay, please?
It is wild clay that I dig and process myself. I have absolutely no idea what cone it is.
@@AncientPottery well, maybe tell us what temp vitrification happens? I’ve got wild WI clay I’d like to try firing.
There's no way my neighbors wouldn't be calling the fire dept after seeing all that smoke coming out of the kiln at around 6:25. Yeah it's hot af, but all that smoke is gonna get people's attention.
Hot tip; fire after dark so the neighbors won’t notice the smoke.
So why not use fire brick and just stack dry?
Dry stack can work but you are also allowing a lot more oxygen in, kind of changes the equation
Hi, this is incredible. I am so inspired. I have done a successful pit firing in the past. My question is : would it be possible to add salt during this process to create those soda ash kiln results? Or does the temperature need to be much higher ?
Thanks! The temp would need to reach something like 1300 C to do a salt glaze, which is way hotter than I have been able to achieve yet. Although I am still messing around with getting the temperatures higher. New video coming out about this soon.
Is the kiln a time machine? You went “back in time”. Make a video on how you did that, it would go viral. Put it in the doodlydoo.
I do it all the time. The secret is buried in my content so you have to watch ALL of my videos to find the answer.
have you ever thought of building a rocket stove kiln?
I think this kiln is based on the same principle isn't it? If not, how would a "rocket kiln" differ from what I have here?
@@AncientPottery I guess it might involve an insulated chimney with the pottery above, and a metal container over the whole lot.
My concern is getting past the HOA
Call it a barbecue. I hate HOAs.
@@AncientPottery I will be building this is Chino Valley Arizona outside of Prescott. Will the cooler weather be a concern?
Interesting I looked at some ( how to use a pottery kiln ) on you tube , temperature ranges for cones etc things to do and things not to do , I see a few mistakes you made , bisc temperatures as to final ceramic temperature etc , I recommend checking out a few videos on using a pottery kiln then apply those techniques to yours and see how it goes. Very good job on your kiln by the way , practice makes for great learning. 👍
Mistakes? I teach my students that there are no right and wrong answers with clay and yet you say I made mistakes? I have been firing earthenware pottery myself for over 30 years. What do you think was my mistake?
Maybe take some bricks off the top or open them up a little , good luck🤞
How to wear such a shoe
An electric kiln heats up very slowly. Shouldn't you do the same thing when you use a wood fired kiln? Slowly over 7-10 hours gradually increase the intensity of the fire?
True, but since this little kiln only holds a couple of pots at a time, can you imagine tending this for 8 hours just to fire 2 pots? Besides, add a little extra temper and there is no need to worry about thermal shock.
@@AncientPottery That reminds me of another question I've had watching your excellent videos ... When they sell clay at the art supply store, is there any way to find out what is in it, and how much and what kind of temper they add? I looked at few on-line suppliers and they say what the different types of clay they sell are good for but not what is in them.
Wow,i thought it would only reach 600 c.
Next time I am going to try to go hotter yet!
Those infrared temperature sensors are not accurate. You will get wildly different readings of objects at the same temperature depending on what they are made of. Reflectivity plays a role in this, as it varies a lot for different materials. For instance, temperature readings from reflective metal are going to be very different from a non-reflective material. Infrared sensors are really only useful to give relative readings of the same object over time, they should not be used as an accurate measure of temperature. The thermocouple should be your only guide to the temperature.
Thanks for the info, good to know.
Maybe a bigger firebox, not sure.
Yes, that might work, I’ll be trying it again soon.
You shouldn't have had such a high entrance to the kiln all you are doing is introducing air that will not contribute to burning the wood. What you should do ideally is have most of your air coming from below where the fire during the vitrification process because you need like 1300C+ to get to that point which for kiln firing you really should be aiming for vitrification.
Personally how I would do it is having the bottom if the kiln made up of halve bricks with a half brick space between each brick or if you don't want to cut bricks in half have them facing long way out then putting the bricks ontop of the bottom layer centred on the space between each brick below them, then reduce the diameter of the kiln by ~25% by layering the bricks ontop removing a brick from each layer but having no gaps thereby reducing the dimeter of the kiln, then at the point where you have reduced the diameter by ~25% put in a grate where the fire will burn, build up about 2 more brick layers then leave holes on opposing sides in the kiln where you want to put in your firewood.
You will want to have doors that you can close and open easily where you put in the wood. You can just build it so you can put bricks in to block off air intake, but it will make using the kiln a pain in the ass so I would strongly suggest proper doors which can almost completely block off air intake and you can slowly adjust how open they are. This is because while you don't need free oxygen when in the sintering process you do need free oxygen to burn off the carbon build up which vitrification needs a lot higher temperature than you need to burn off the carbon so slowly opening the doors in the as a final step will be where you burn off your carbon.
anyways the rest is the same in the build process so it doesn't need to be described
Usage however is a little different obviously you put in your firewood to slowly build up the temperature then after you have put in enough firewood slowly close the doors over about 20 minutes adding more wood as you go to replace what has burned off, then leave it going only opening the doors to add more wood then when the pots of gotten white hot 1300C+ very very slowly open the doors only at first leaving a millimetre gap also adding in firewood to keep the fire at the same intensity, then after the door are completely open keep the fire going at the same intensity for at least 30 minutes this is your final step to burn off the carbon, then finally as the fire starts to dry down mostly close the doors to allow the temperature of the pots to slowly come down.
If you want to be extra careful you can add insolation to the kiln so that the pots will cool down even slower.
I have no desire to reach 1300 C or vilification. I am making earthenware and am perfect happy with 800 C, but hopefully your comments will help someone else here who is trying to reach those temperatures.