Salt and Soda firing a Wood-fired Phoenix Kiln
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- Опубліковано 25 чер 2024
- This video takes viewers through a firing of my wood-fired pottery kiln, including a quick tour of the kiln and a view of the pots that come out. It was made for the members of West Forest Potters during the coronavirus lockdown in April 2020.
Thank you so much for posting a video as such. It greatly helped a pottery enthusiast like me to understand the mechanics of kiln building and pottery firing.
Thank you. Getting ready in the next month to do my first salt and soda firing in a Catenary Kiln. The process makes much more sense now that I have watched your video.
This was so informative and fun to watch your process. I am just a beginner so watching you was a extreme boost for me. Thank you. I hope you have many more videos. 😊
Excellent video Kevin, thank you for sharing. Beautiful firing results so inspiring!
What a great kiln! And absolutely lovely result! Greetings from Finland!
Good job. I like your kiln. I built an olsen wood fired kiln about 30 years ago. I run a gas trolley kiln now but have always wanted a salt fire wood kiln. It has a natural beauty that is very impressive. Thanks for your video. Wolfhound Pottery
You know your kiln well...a great firing! Thanks.
Great work !
From Addis Ababa, Ethiopia 👍🇪🇹
Nifty! Thanks for sharing. I do like your kiln design.
Thanks for the tips. Nice work and kiln!!
The simplicity but well designed pots are superb.
Thank you Jim
Wow! Very nice kiln and pieces. I want to make an smaller version of this kiln. Hope I can do it this year. Congratulations and thanks for sharing!
Wow Kevin, what a successful firing! Your pots are just beautiful! Félicitations!!!
Very nice! Thank you for sharing. You’ve convinced me to build a gas kiln.
thank you sharing your knowledge. we are trying to learn wood firing and this video is so usefull thank you again
Great! I'm planning to build one myself soon! Very inspiring and useful information!
Don't use steel firebox grating if you can help it, otherwise if you do porcelain, it will look like flys have been on it.. Austenitic stainless steel or brick cheqering
Very interesting Kevin❤️ thank you a lot🙏
Beautiful work!
Thank you Ariane
Really well edited kevin
Very well done. Thank you. I was impressed at the ease with which it reached cone 11.
Thanks. The kiln has a relatively large firebox and chimney, which makes it easier to get to temperature.
@@kevinakhurst7855 I omitted to say how delightful and varied your pieces are, and how beautifully thrown and formed. The large bowl is a stunner, but I think my favourites are the variations on a theme with the simple decoration and the harmonious colours.
Thank you for your kind words. If you are interested in seeing what came out of the kiln recently you can find it here - www.kevinakhurst.com/2023-work.html
Xcellent results
Very beautiful artistic pottery.
so informative, thanks
Thanks for sharing the video. Concise and informative, and I enjoyed watching it. Now that you've fired it a number of times, are there any design changes you wish you made, or adjustments you would recommend to others wanting to build a Phoenix? Thanks in advance.
Thanks Nate. I haven't thought about that before so your question got me thinking. I don't think I would make any major design changes. I used castable for the firebox arch/chamber floor and also for lintels over the sliding dampers and in every case it cracked in use early on, so I would probably research my casting methods and also possible alternatives, but having said that the cracks haven't caused me any problems yet. Also, as a previous comment picked up, I don't really use my mousehole effectively and I might review the design of that. I would like to mention how pleased I have been with the use of high alumina lightweight bricks for the interior chamber walls. These have been very resistant to attack by salt and soda. The other challenges I have encountered, such as the temperature variations within the chamber and the uneven distribution of salt/soda, I have chosen to accept as features of the kiln design and work with them. I hope these comments are of some help.
Excellent. Nice pieces of works. One of the pieces at 19:23 with light green is so pleasing that I would fight for it. What did u use for its coloring ?
Thanks for your kind words. The green pot is coloured with a slip containing cobalt and titanium. The cobalt gives blue and the titanium a yellowish colour; with the right balance between them you get this nice green with a very slight variegation, presumably from the titanium. I got the idea from the Scottish potter Fergus Stewart.
Followed the video with much interest. Congradulations for the beautifull pots. Would have liked to see the smoking degree of the chimney. Would it be possible to share a plan of the kiln? Thanks a lot.
Thanks Dayanath. It doesn't smoke very much. Once I go into reduction there is a puff of smoke each time I stoke, that quickly clears. I don't have any plans which are designed for others to view but I do have a couple of rough drawings which you might find helpful. If you email me (address on my website) I will reply and attach them.
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Very informative thank you. doesn't the soda eat away at the soft hti bricks?
Thanks. The kiln walls are two bricks thick and the inner wall, which lines the chamber, is made of 28 grade bricks which have higher alumina and lower silica. More expensive but more resistant to salt. I’m very pleased with how they have performed. Unfortunately I couldn’t buy tapered arch bricks in 28 grade, so I will probably end up replacing the roof when it gets worse.
Hi, I love your kiln. Good job and thank you you making the video. Do you have a link to plans if I were to build my own?
Hi thanks Jesse. I don't have plans that were intended for others to use, but I can send you what I have if that is of any interest. Email me at kevin.akhurst@btinternet.com if you would like them
Great video Kevin. Enjoyed watching. Can you say why you use soda and salt together, and why not inject directly into the kiln chamber?
Thanks John. The use of salt and soda on wooden boards in the firebox was suggested to me by Jeremy Steward, who told me he had got good results that way. I did try spraying soda into the chamber once, but had a difficult time with the spray nozzles blocking and, ultimately, melting. I could have overcome that, but I was happy with the results from Jeremy's method so I decided to focus on optimising my slips and glazes for that approach rather then spend more time exploring the firing technique. I think having the sodium carried with the flame increases the variation in appearance around the pots from front to back, which I like. I know there are supposed to be differences between salt and soda - I believe that salt is supposed to fill the kiln more quickly while soda tends to follow the flame, and I have also read that they have slightly different colour responses, though I don't understand why that should be given that the active ingredient, sodium, is the same for both. From where I am now I don't want to spend time trying out variations on that combination.
Thanks for detailed response Kevin. All makes sense to me. All best John
Great job on video..as a newbie to wood fired pottery it would be nice to know the different stages of firing, sequence, sop.
Thanks Timothy. I am firing bisque-fired pots so I don’t have to be super slow at the start, but I still like to go a bit slow to start with in case there is any moisture in the pots and I start off at 150 degrees (Centigrade) an hour for three hours. Then I increase the ramp to 225 degrees an hour until I get to 950 degrees. At that temperature I go into reduction by closing dampers and reduce the ramp rate to 100 degrees an hour. Once I get to cone 9 down near the top of the kiln (around 1250 on my pyrometer) I hold temperature for about two and a half hours while I add salt and soda at ten minute intervals. I hope that helps.
Excellent kiln firing schedule!
I love wood firing.
Thank you !
very nice congratulations. I would like to make a smaller one. I don't understand at what height the outlets of the firebox are; in addition, the dimensions of the hob with respect to the arch of the hearth.
Sorry for the delayed response - I missed your comment somehow. I'm not altogether sure what you want to know. There is a single outlet to the firebox which takes the form of a gap in the firebox roof/chamber floor at the far end of the kiln. The hob is formed of solid steel bars which are the full width of the firebox. However, I did lay two single rows of bricks on the firebox floor to make it easier to create the ember bed by reducing its width.
Hi Kevin
What material of kiln shelf & props are best in the reduction salt & soda firing ? Thank you. I have learned a lot from your sharing the video. From Addis Ababa
Hi. I'm glad you have found the video useful. I'm not an expert on kiln furniture, but I use ordinary cordierite shelves and heavy fire bricks cut to various sizes for the props. The kiln shelves are coated with batt wash on the upper surface (not on the lower surface as I don't want bits flaking off and falling on the pots beneath). After each firing I scrape off any loose batt wash and brush more on where the shelf has become exposed. If you are planning to spray soda you should avoid light-weight silicon carbide shelves as the thermal shock of the spray cracks them.
I should have mentioned that I also dip each end of the kiln props in batt wash, as well as using wadding pads between the props and the shelves
What is the lumps you put under to stand on the shelves and how do you make it? Beautiful oven and pieces!!!
Hi Mirjam. Thank you for your comments. The lumps are wadding, to stop the pots being welded to the shelves by the salt/soda glaze. People have many different recipes for wadding - the important thing is that it should contain a lot of alumina, which doesn't react with the sodium. My wadding is made of two parts alumina, two parts of a fine grade molochite and one part of china clay, with a little wallpaper paste added to help it bind together. The dry powders are thoroughly mixed and then small amounts of water are mixed in until it all just binds together but is still a very stiff mix. I'm very happy with the way it performs.
Maybe I should add that I think many potters put the wads on the pots as they load the kiln, but I prefer to fix the wads to the pots beforehand with small blobs of PVA glue.
@@kevinakhurst7855 thank you very much for the answer
Are the pots bisque fiired first and are you also glazing them along with salt firing?
Hi. Yes I normally bisque first as I find glazing easier and the glaze firing isn’t too long when I’m firing solo. I did fire some raw glazed pieces once as they were too big for my bisque kiln. For that one I started firing one day, closed the kiln up for the night and then finished firing the following day. I used to always use slips in the top half of the kiln and glazes in the bottom, where the temperatures and amount of salt/soda are lower. More recently I have been putting glazes high in the kiln, where they are usually changed by the salt/soda
hi kevin,
you mention at 13:53 that when salting you aim to keep the temperature between 1220 and 1260 degrees. this seems quite a small range, what problems would you have if you were off one way or the other?
Hi. For me this is mainly about reproducibility. I only fire about twice a year and I don’t want to start experimenting with different firing regimes when I have six months of work inside. The salting takes over two hours and at the end cone 12 is most of the way down at the top of the kiln. I think if I allowed the temperature to go much outside that range over the salting period then my pots might be over or under fired. I have heard more recently about lower temperature soda firing, so I think it must be possible, but I’m already well down a different path.
How many fire bricks total did you use in this kiln?
Hi Nathan. Sorry, but I never counted them. I got a lot of bricks from an old kiln and I have a lot left over. Almost all of them are standard 9 inch x 4.5 inch x 3 inch bricks, although I used some larger heavies at the chamber floor level to help key in the cast floor. Sorry I can't be more help
I like your kiln is there a place I can go to get the dimensions, material list, and designs
I’m afraid I don’t have details in a fit state to be shared. I measured up a friend’s kiln, made some design changes and then built it from my own sketches and notes. I think there are some Phoenix designs on the internet but I expect each one will be a bit different
these white things that you use to place under the pots in the kiln, what are they made of?
Hi Olga. It is called wadding. Without these, in a salt or soda firing, or a wood firing with a lot of natural ash glaze, there is a risk that the pots will be attached to the kiln shelves by glaze during the firing. With wadding it is important that it doesn't vitrify during the firing, or react with the salt/soda itself. It needs to be firm enough to support the pot and friable enough to break off easily after the firing. I make mine to a recipe I got from Micki Schloessingk; 2 parts of a very finely ground alumina, 2 parts of a finely ground molochite and 1 part china clay. These are mixed with some dry wallpaper paste powder (or courgel) as a binder and then water is stirred in to get a very stiff consistency. Some potters apply these as they pack the kiln but I prefer to wad my pots before packing, fixing the wads to the pots with small blobs of PVA glue.
@@kevinakhurst7855 Thanks a lot for the answer, Kevin! I want to try salt firing but I am not sure about the complete technology. Would you mind answering a couple of more questins please? Does the salt affect the inside of the kiln and the shelves? can you use your kiln chamber for both salt firing and other kinds of firing? do you salt fire at cone 5 (or am i mistaken)? and placing salt should happen at the highest temperature point? for how long then should I hold this temperature? thanks in advance for reply!
@@olganikolayeva2568 Hello Olga. I will answer your questions, but I recommend you get a book on salt firing (e.g. Phil Rogers, 'Salt Glazing' and Jack Troy, 'Salt-Glazed Ceramics'), which will go into more detail. The salt does gradually attack the inside of the kiln and this generally rules out using normal lightweight insulation bricks. Many potters use heavy bricks but I used high-alumina lightweight bricks for the lining of my kiln chamber and they are resisting the salt well. I use normal cordierite kiln shelves most of the time and I coat the upper surfaces with kiln wash to reduce the attack by the salt. They are still going well after 15 firings. I understand that the salt which remains on the walls can affect subsequent non-salt firings, but maybe in a small and acceptable way - I haven't tried it myself. I usually start salting at about cone 7 or 8 which is close to my maximum temperature. I then gradually add the salt over around two hours while holding at that temperature, by which time cone 11 is down at the top of the kiln and cone 9 at the bottom. You need to give the salt time to act on the surfaces, but there are no strict rules. I hope this helps. Good luck with your salt firing.
@@kevinakhurst7855 thanks a lot! I will read these books if I find them!
Hello, would you have the design of this oven? I'm from Brazil and here I can't find books that teach how to build. I work with amphoras, and I would like an oven like this
Hello Silas. Sorry but I don't have any design details that would be intelligible and are in a state to be shared. I read quite a few books on kilns before I started (e.g. Olsen, Kiln Book; Gregory, Kiln Building; Finch, Kiln Construction, Lou, Art of Firing; Rhodes, Kilns), but what I found most useful was to find a friendly potter whose kiln worked and develop the design from theirs.
@@kevinakhurst7855 Thank you very much
I prefer comercial glasses they are much better and the foreign will last less time to reach the glass melted.
Are you burning pine? You are getting ALOT of creosote spoke and ash build up. Forgot to mention…if you put a cast iron lidded pot in there you could have a hell of a “potters stew”.
Yes - quite a bit of pine, mixed with holly and birch. It’s just what grows locally. Also, later I discovered that my firebox floor had collapsed and blocked my mousehole, so now that is fixed maybe the embers will burn out a bit more. I wish I had a horizontal flue I could put a cook pot on top of - maybe my next kiln?
いいねー
ありがとう
A proper mousehole under the firebox would eliminate coals clogging the entrance flue.
Thanks Gary. I did build in a mousehole, running through to a perforated floor at the far end of the firebox, but when I started firing this kiln I felt it didn't make much difference and since then I have left it plugged. Your comment has inspired me to try using it again.
@@kevinakhurst7855 A proper mouse hole, perforated bricks clog. See "Pioneer Pottery" on basic construction. I modified mine bit I get no coal build up in my throat arch. I just happened on this again. Hope you are having decent results. I been on a long break but might build again in downtown Detroit.
Thank you very much Kevin for this clear and inspiring demonstration. Much appreciated. :)
Gabriela