Sunday, March 22, 2009

My Woodfired Kilns, all 7.

Kiln Number One.


I had not seen a wood fired kiln, other than in photographs, before I built one. My friend, Peter Watson who got me started with potting, kindly lent me books and magazines. One book, "The Craft Of The Potter" by Michael Casson, had a plan in it for building a small wood fired kiln that could be used for raku or small earthenware pots. I bought some second hand fire bricks from a demolition yard, and made my first kiln, largely based on the plan in Michael Casson's book.
I had no idea if it would work, and was concerned that it might be too smoky, so I built it almost out of sight between the back of our house and the shed where it was screened from the main road and from neighbours. I fired it once to 1100 degrees Centigrade in little over 2 and a half hours. The clay that I put the cones in exploded and scattered bits of cone and clay over some of the pots and glaze test tiles that I put in, but I was really excited by the apparent ease of achieving a useful temperature and demolished the kiln so that I could use the bricks as part of something much bigger!

Kiln Number Two.




Kiln number two was a round up draft kiln. The chamber had a beautiful chequered floor that I gleaned from Michael Cardew's "Pioneer Pottery". Some other ideas were gathered from a book on making kilns by Ian Gregory. I also had ideas of my own, notably an attempt at a modified Bourry firebox. In its favour, the kiln did look very sculptural, and rather pretty in some lights, and there was opposition from Laura to the idea of pulling it down, but the fact of the matter was that the kiln didn't work!

Kiln Number Three.



(The photo above shows my friend and teacher, Peter Watson, and myself examining the results of a firing of kiln number three.)

I added a chimney to kiln number two where the firebox had been and converted it from an up draft to down draft kiln. I removed the top of the chamber and made a roof for it with an old kiln door. I made a new firebox on the same side as the kiln door. The firebox was of greater area than on the previous kiln, but was shorter and squarer. The firebox had to be partly demolished to enable the kiln to be loaded and unloaded, which was annoying. The firebox was also horribly low which meant that a day's stoking was really hard on the back and the knees. I did managed to nurse the kiln to around 1060 degrees Centigrade after a stoke of 8 or 9 hours, and fired some rather under done earthenware pots. I demolished all but the chimney of this kiln after one firing and designed something that would be easier to stoke.

Kiln Number Four.





Kiln Number Four was the first kiln that really worked. With the knowledge gained from the first three attempts I went back to the drawing board. I wanted a kiln that would be easy to stoke, and that would give a strong flame flashing effect on the pots. I put the firebox crosswise, and, dispensing with a bag wall, fed the flame in near the top of the chamber, and zigzagged it downwards to be collected at the bottom of the chamber below the lowest kiln shelf. On the way to the chimney was a second small chamber that had room for one or two pots. I used an old kiln door for the roof of the chamber, and recycled fire bricks for the main kiln construction with an outer layer of ordinary red house bricks for insulation. I had a really successful, and enjoyable firing of my first earthenware watering cans and some other smaller pots. The work was fired raw, and I found the firebox a pleasure to stoke, and the temperature rise easy to control.
The top of the chamber fired hotter than the bottom, this was as I predicted. More importantly, the top of the chamber had really good flame flashing, and the pots that were on the top shelf toasted up beautifully.

It was with real sadness that I later demolished this kiln and made way for kiln number five, as kiln four had real potential. The main problem was the small chamber. Also, the strong flame flashing suited unglazed work, but would have been a problem for glazed pots.

Kiln Number Five.






Kiln Number Five, a round up draft kiln, does work quite well. The firings take about 5 to 6 hours to get to 1200 degrees centigrade in the lower part of the chamber. The kiln is quick to cool down, and can be unloaded the day after firing it. The kiln has three levels of triangular kiln shelves that are arranged around a central prop like segments of an orange. Little gaps in between the shelves allow for the heat and flame from the firebox to rise through the chamber. The lowest part of the chamber is much hotter than the top, but I can rely on about 1200 degrees on the bottom shelf, around 1150 on the middle, and about 1060 on the top shelf. Glazed pots can turn out well in this kiln, and pots can also get strong flame flashing on the lower shelf. It is possible to fire too quickly with this kiln (in excess of 400 degrees centigrade per hour gain), or to loose heat fast if not fired with care. Above 800 degrees centigrade, the kiln is also likely to go into strong reduction if too much wood is put on at a time.

I still have this kiln, but have made kiln number six, an even firing down draft design, to get to stoneware temperatures.

Kiln Number Six.






Kiln Number Six is my production kiln. I mostly fire it to cone 11 to 12 in about 12 to 13 hours, although it could get there much quicker. The kiln was built mostly with new fire bricks. There is a layer of hard brick within the chamber that is backed up with K23 insulating fire brick. K26 insulating bricks form the arch. The kiln was inspired by a much smaller gable arched wood kiln designed by Jim Schuld that I saw in a Ceramics Monthly magazine. My kiln differed quite a bit from his design, but I liked his fresh ideas and his use of unusual materials, and the article was a great help in getting me started. I will write an article about my kiln, with some diagrams, so won't go on at length here.

Kiln Number Seven.



(Top photo shows my friend, Dave Sharp, casting his expert eye over one of the raku pots. Dave is an enthusiastic raku potter.)

Kiln Number Seven, is a small raku kiln. It is capable of reaching 1000 degrees centigrade in about two and a half to three hours. Whilst taking out a load of pots the temperature in the chamber drops to about 600 degrees, but is back up to 1000 degrees in 20 to 25 minutes. I use a cross draft firebox, and, because of its short length, the front part of the chamber is fairly oxidizing and the back part tends towards reduction.

30 comments:

judy shreve said...

Great post - what an adventurer you are. You have definitely learned by doing. What time frame is this from first kiln to kiln #6? I took a kiln building class at the clay center where I'm an apprentice. It's a small gas kiln -- but the man leading the class is very precise & we did a lot of planning (and math!) before laying the first brick. I don't know if I'll ever live where I can build an atmospheric kiln - but on the bright side - I'm beginning to really understand my electric kiln & slow cooling to develop my matte glazes. And I'm excited to work with earthenware soon too.

Peter said...

Hi Judy, I've been prompted by your comment to look back through some photos to work out when I built the kilns. It would appear that I started potting in February of 2004, as the first photos of fired work were from March 2004. The second hand fire bricks that I purchased to make my first kiln arrived in March 2005, and I had built kiln number 3 by May 2005. Kiln number 6 was started August of 2006, and had the first fire lit on 5 November 2006.

I have come to potting rather late (I started in my mid 40s) so I have felt the need to make up for lost time, hence the somewhat frantic pace of kiln building. In some ways I think I learn faster then I did when I was in my teens (maybe we learn cunning as we get older!), but the body has more limitations now. I do wish I could be an apprentice potter for a few months at least to get more idea of the everyday routine of a production pottery,and also see other people making pots. I'm not sure that anyone would be interested in taking on an old fellow like me though.

I am still using an electric kiln for some of my work, and will post some photos of the latest glaze firing soon.
Best Wishes, P.

Hannah said...

fab post! I love it, thanks for showing that. really interesting stuff. that'll spur me on

Judy Shreve said...

You built all those kilns over a very short time. WOW. It's great how each kiln got progressively better - you certainly were able to see what needed to change & improve after firing each one.

I've enjoyed my apprentice time at the clay center where I am. I've learned a lot not just from the facility - but from all of the folks who take classes there. I also came to clay late & have only been working in clay for about 10 years now. Being older does help you understand priorities - maybe that's why we learn faster -- and make a good apprentice -- don't let age stop you from trying to find an apprentice position.

I'm very interested in seeing your electric kiln work & glazes. Looking forward to those photos.

Peter said...

Thanks for those comments Judy and Hannah, lovely to hear from you both. Regarding the electric kiln glazes, I will do a post really soon with some photos. I have actually been glazing another kiln load for the electric kiln this morning, and hope to fire them tomorrow. I'll be demonstrating throwing on my wheel on Sunday at a small gallery a few miles from here. So I'm having some nervous flutters! Thanks also Judy for the encouraging comments regarding being an apprentice, age, and late starts. I'm definitely doing a lot of thinking about the next few years so, who knows, is there a potter out there who wants their floors mopping!!??

Sylwia said...

I wish I had just one, ehhh...

Peter said...

Hi Sylwia,

Thank you for following my blog, and for your comment. It is good to hear from you. It is also good to hear from someone in Poland. There are quite a lot of Polish people in New Zealand, and my wife (although not herself Polish) is invited on a regular basis to exhibit her paintings with the Polish Society in Dunedin.

I have indeed been fortunate to have been able to build wood fired kilns. I do love what wood and wood ash can do to a pot when it is fired, and enjoy the way that wood firing can be such a continuation of the creative process.

I have enjoyed looking at your blogsite. Sadly, I do not speak Polish, but it is good to see the photos. You have very interesting work.

I tried to post a comment on your site, but could not work out how to do it.

Best Wishes, Peter.

Anonymous said...

hello there peter. i stumbled upon your site whilst looking up plans for a simple, working kiln that i can build myself. and i found 7 of your designs! perhaps you could give me a few pointers on how to get started. you do make it look easy! i've only ever fired in gas and electric, and now that i'm living on a bush block without electricty, i'm keen to fire with wood. how do i begin? ps. thank you for this lovely blog. i'm off to explore it more.
claire

Peter said...

Hi Claire, welcome to my site. I am really happy to help if I can. I was wondering about drawing some simple plans of the better kilns and putting them on my site, so this I will try and do. Just rather busy this week with working towards a firing, but will do something about some helpful information for you probably next week. (I'm writing this Monday 15 June). Best Wishes, P.

Anonymous said...

thanks Peter. wonderful. i await them eagerly!

ang said...

nice bit of kiln building the raku one looks a treat, well done..

Logan Frostt said...

hello peter it does appear to me that i am quite late to join this conversation however i must ask if you know much about Kilns made for Metal working/Blacksmithing. i have worked with light metals and shaped them without heat but ive progressed to denser metals and need a kiln finally XD if you could please lend me a hand =P btw wonderful job on the kilns keep it up your doing great

Peter said...

Hello Logan,
Welcome to my site. I am sorry to say that I know nothing (as yet!!) about metal working or blacksmithing, so I really can't help you regarding kilns for that. I had a quick search online with Google for blacksmith forge plans, and came up with a lot of photos and some plans when I did a Google "Images" search.
I noticed that you said "kiln", rather than "forge" or "furnace". I found a site that might be of interest (??)

http://www.artfulbodgermetalcasting.com/3.html

Sorry not to have been of more help, but I am sure that there will be someone out there who will have useful information for you.

Good luck with it. It would be nice to hear how you get on.
P.

Anonymous said...

Hi Peter,
I would like to build my own kiln but I don't have a large backyard.
You second kiln looks small enough.
It would wonderful to see the construction drawings or something that could help to copy you kiln.
Faithfully yours,
Ilia,
Minsk, Belarus
Sirius2@rambler.ru

Anonymous said...

Sorry, it's a question for the fifth kiln:)

Peter said...

Hi Ilia,

Lovely to hear from you, welcome to my site.

Sorry not to reply sooner, I have been very busy here over the last few days, and have had not much time on the computer. Unfortunately I did not draw a plan of the 5th kiln, but just made it with what I had available at the time.

I did find some nice looking plans of a simple round updraft kiln in a book called "Self Sufficient Pottery" by Judy Cunningham-Smith and Mollie Herbert. The book was published in 1979, but there are a copies available at very reasonable prices second hand through Amazon.com and AbeBooks.com

Sorry not to be more helpful now, but I am rather tired after a long day. I will try to send you some more information to your Email address.

Best Wishes,

Peter

Anonymous said...

In your first kiln I was astounded how quickly it took you to reach over 1000degC - well done! Means anything is possible. I'm making a small one in my BBQ using the extra strong firebrick recipe from Forno and rocket stove technology - design.

Peter said...

Hi Anonymous,
Good to hear from you. I was astonished by getting to more than 1000 C so easily, and it was really exciting to find that it could be done. Good luck with your BBQ kiln, it sounds fun, do let us know how it works out! P

Anonymous said...

Thanks for putting up my comment, I like your wife's paintings too! Really contemporary and colourful. I was wondering if you have any advice with clay dug from the ground in your backyard. I'd like to make a throwing earthenware that fires to around cone 01 - 2. Do you have a recipe or experiences to share by any chance? Thanks!

Peter said...

Hi Anonymous,
Using clay from your own backyard is quite a big topic for me to answer properly as a short comment, I would really need to do a post on it. I had a very quick look on line as I know that other people will have put together "howto" advice on this. One site that could give you the information that you need to get started is
http://www.practicalprimitive.com/skillofthemonth/processingclay.html

This has good information and step by step photos of processing clay that you may find helpful.

The clay that is in most people's backyards where I live (and gardener's complain about!!) is a nice earthenware that fires to the cone 01 - 2 range that you mention.

Good luck! P.

whisperingsage said...

Pete, this is soooooo exciting to me, thank you for making all the mistakes so we don't have to. I for one, DO appreciate your learning curve.
My next question and suggestion; have you ever heard of the Rocket stove? We have been learning about them and using them for a few years and the concept is best found on a page that I probably can't put up or it will be tagged as spam. But, go to Google and type, rocket stove, Paul Wheaten,Rich soil. This is the Permies site which has loads of neat DIY ofo, and this rocket stove concept is the best thing I have found to heat your home, greenhouse, even tent. The "rocket" part of the stove is the heat riser, which is above the woodfeed.(which is vertical and the fire is drawn in sideways. ) and that area because of the vortex, creates amazing smoke dissipating abilities. So the "mass" of the mass heater can then absorb the rest of the heat with long lasting comfort in the home. watch the videos and see. But there must be a way to marry these concepts with a kiln!
Also, the gross reduction in smoke will make you a better neighbor.

Peter said...

Hi Whisperingsage,
I don't usually publish adverts here, but in this case I'll bend the rules, the Google search that I did confirms what you say, the Rocket stove looks a great idea! I am always interested in ways of using fuel more effectively. Thanks for the information. P

Lisa researching ceramics said...

I looove your kiln! Thanks for sharing pics.

Peter said...

Thank you Lisa, it is good to hear from you. P

Kirk Bonds said...

Interesting and wonderful. My goal is a small wood fired kiln dedicated to terra cotta with no glazes. Where can I go to find information on constructing such a kiln. Pieces would be maximum 20" square and possibly as tall as 24". I am looking for possible kiln designs among Pueblo Indians, Mexico, Central and South America. Any thoughts? I am at quannah2@mac.com. Thanks for your hard work, sharing, inspirational and useful information.

Peter said...

Good to hear from you Kirk,
It should be fairly easy to build a kiln for terra cotta temperatures. I was wondering how many 20" square by 24" tall you were wanting to fire at a time? The other important thing that could be a factor in kiln design is if you are out in the country somewhere with no near neighbours and no fire restrictions? Or if you are in a town?


The Kiln Book, by Fredrick Olsen is one of the best starting places for getting an overview of kiln design. You will find that book at amazon.com, or many other book sellers. Many potters built kilns based on Olsen's fast fire wood fire kiln, but there is good information about tradional kilns in the book that could suit earthenware better.

One problem I can think of straight away for you with a "modern" down draft fast fire design, is the size of kiln shelves. Your 20" square work would essentially take up one large kiln shelf, and an "efficient" wood fired kiln with a chamber of maybe 20 - 30 cubic feet, might not fit many of your pots in it. It is possible to fire a kiln like that with very little smoke being generated (which is good if you have neighbours or fire restrictions), but you may find a simple updraft design a much better proposition if you were firing lots of larger earthenware pots. You would almost certainly generate more smoke though! I will email you as well with this.
Best Wishes,
P

Lisa loves pottery said...

Your kilns and your pottery are beautiful!

Peter said...

Thank you Lisa. :) P

Anonymous said...

hello,
im a young potter that has been raised in and around earthenware all my life.Now a young potter of 33 years old and over 25years of potting i have been searching for small designs of wood fired kilns for a couple of months and was wondering if you could send me in the right direction for advice so many questions i have about this process in my head any ideas would be appreicated

Peter said...

Hello Anonymous,
Good to hear from you, thank you for having a look at the blog and for writing in. One very practical book that springs to mind is, "Kiln Construction: A Brick by Brick Approach" by Joe Finch.
If I had found a copy of this when I first started trying to build a wood fired kiln, I think I would have made even faster progress. This is a fairly short book, and you will easily read through in an evening, but the practical examples of kilns that he gives are a good starting point, and look like they would work well and be easy to build and to fire. The kilns that are described in the book are for wood or for gas, or for a mixture of both. The kilns use modern materials, such as insulating fire bricks, and would fire economically.

In one of my comments above this I also mention "The Kiln Book" by Fredrick Olsen, and this is also a very worth while book to study. This is a much longer book, and has lots of information about kilns in general, as well as specific examples. Many potters built versions of the Olsen Fast fire kiln that is covered in this book. The kilns by Joe Finch seems to me to be a further refinement of Olsen's Fast Fire kiln, and it is interesting to compare them.

Hope all that helps.

Best Wishes, P