Tuesday, 14 August 2012

Mini wood-fired kilns..a possibility?

Two questions I'm seeking answers to at the moment:

- is it feasible to build a mini wood-fired kiln?
- if so, what is the highest temperature it could be fired to?

I'm exploring the possibility of designing a very small kiln for use in a suburban environment, so ideally it has to produce no more smoke than a household barbecue. Last week I created a simple up-draft prototype using normal house bricks to build a firebox and a kiln chamber and chimney made from cylinders of kiln fibre. The chamber was large enough for around nine small-to-medium pots placed on two layers of shelving.

The kiln was stoked with charcoal and wood for around five and a half hours (that is to say, until I ran out of fuel!) and temperatures in the firebox were high enough to make the metal grill slump. The 5-inch high ember pile turned pale yellow and the flames a beautiful lavender-blue.

I was hoping to get to high earthenware temperature in the chamber, but we didn't get there...even cone 05 didn't go down, but the temperature was high enough to sinter the fen slip I'd applied as a glaze to the inside of a few of the pieces. By the end, the kiln fibre was glowing a bright orange and you could watch waves of flames surging up the walls of the chamber..it was worth five hours' hard labour just to see that.

One thing I was pleased about was the low level of smoke produced..generally, the fuel burned very efficiently and smoke only became evident when a damper was placed over the top of the chimney. Once things got toasty in the chamber, seven inch flames would shoot from the chimney as wood was piled on..pretty impressive for a kiln less than five feet tall!

This design was just cobbled together using stuff I had lying around..next time I plan to build one using H.T.I. bricks and a second layer of one-inch kiln fibre. I will also reduce the height of the kiln chamber and make the chimney taller...hopefully that will make much higher temperatures achievable.

I've yet to find much on the web about mini wood-fired kilns. If anyone has any ideas or links, I'd be glad to hear about them. I do remember a chap demonstrating a tiny, portable kiln at a ceramics fair back in 2007. It was fired with charcoal, and he reckoned it could reach stoneware temperature. The chamber was miniscule though, as were the pots he put in there.


  1. Hello, sorry for the translation of google

    The small coal furnace you saw in 2007 can be this, a minigama Akira Yoshida.


    The problem is that not withstand multiple firings. So I am investigating a number of cooking pasta without breaking support
    I have built small brick kilns circular BBQ, mineral coal and air (with a hair dryer) + 1300 º c in less than an hour!

    Hopefully get to design a small wood kiln ... is one of my dreams: a mini-Anagama


    1. Hello,
      Thanks for your comment, the minigama design looks interesting, maybe I will get hold of the booklet. I would love to learn more about the use of hairdryers too, that sounds fascinating!
      Very best, Mark

  2. http://www.merkelhess.net/works/2009/spongefactory.php you will find another small furnace downdraft

    this is another Akira oven, based on a traditional Japanese system to heat the house (shirrichin)

    a video on how to build the minigama

    and this is the wiki that makes a friend
    The oven is cheaper, although we are the most beautiful ... works great ...
    you can do just round and cover with refractory ... coal and vegetable mix, put the pieces in the coal or on a piece of refractory ... Put a metal tube at the exit of air from a hair dryer, if not melt the plastic

    if I find photos of some of my cooking you send them

    Try it! is very fast and fun

    1. Wonderful!!! Thank you so much for the links, these will give me plenty of food for thought. The video on how to build a minigama and the wiki will be especially useful. It would be great to see your photos. I am on facebook under Mark Smalley Ceramics.. if you are a member, please do add me as a friend..maybe we could share photos there. Thank you again for your help! :)

  3. When i was in my teens I helped build a combination anagama and catenary arch kiln. The thing was a beast though...10-12ft stack on the back of the catenary arch. But the flow was interesting...still had the normal stoke hole that would be on a catenary kiln...but the anagam was right behind that.
    Anyway, years later i ran into rocket stove mass heater technology. This method of heating is cool cause it reburns the smoke from the initial fire and creates more longer lasting heat from it... Maybe there is a way to combine those systems to make what a mini wood fired kiln.

    1. Thanks for your interesting comment. Funnily enough, I was thinking yesterday about how heat might be collected from the chimney & recycled back into the kiln.. perhaps using a coiled metal pipe inside the chimney and some kind of electric fan system. If you know of any useful sources of information about rocket stove mass heaters, I'd be very interested to take a look at them.