Monday, 13 June 2011

My new Raku Kiln

Here are some photos of my new 'Raku Kiln'. I cut and wired the frame together one day and then lined it the next. Now I am ready to go.





HOW I DID IT - The basic frame of the kiln was made using 2mm guage wire, which i bought on a roll from my local hardware shop (width of 600mm). I cut and wired the frame together with regular fencing wire. Once the frame was made, I partially lined the kiln with aluminium foil, then lined it with 1260c ceramic fibre blanket which I obtained from a refractory supply shop. It came on a 7.2m roll, 600mm wide and 25mm thick. It can be bought by the metre from most ceramic supply shops. I found that it was more econimical to buy it on a roll, plus I want to make other kilns, so why not. I used approx 4m of ceramic fibre and wire to make this kiln. I also used approx 4m of Kanthal Wire and 30 ceramic buttons which I made from raku clay. These were used to fasten the ceramic fibre blanket to the wire frame. In the photos, you will see a hole at the bottom where the gas burner will be placed and the hole at the top is the flue. The dimensions of these holes is quite crucial in order to achieve the required temperature and atmosphere within the kiln. I will know if I have to adjust these once I do my first firing. When firing, I will place the kiln on an base of bricks seperated by another layer of ceramic fibre to prevent heat transfer through to the bricks from the kiln.

HOW TO RAKU FIRE- Pots are glazed, dried then placed on a shelf which sits inside in the kiln base on approx. 10-12cm kiln shelf props/furniture. The gas burner flame is directed through the hole in the bottom (secondary air), under this shelf and hits a tilted kiln shelf/ledge at the other end of the kiln and flame directed up and other the kiln arch (see pics). 



Burner directed under shelf and flame hit a tilted shelf at the other end of kiln and directed up and over arch.
View inside showing set up (note tilted shelf sitting on the floor at the other end) which assists direction of flame.

Pots are quickly fired/heated until they reach approx 900C to 1050c, depending on the maturing temperature of the glazes used on the pots. Once the required temp has been reached, they are then pulled from the kiln using long metal tongs and wearing heat resistant fire gloves as the pots are GLOWING and RED HOT. The time that the kiln takes to reach the required temp does vary from kiln to kiln and also depends on the operator, but generally I have pulled pots from the kiln within an hour and a half. The glowing pots are then placed into metal bins which contain a reduction material (for example newspaper, sawdust, leaves, straw). Once they ignite, a generous thickness of damp/wet newspaper, then a metal lid is placed on top of the bin to enclose and starve the pot of oxygen. A chemical reaction occurs within the glaze and clay body due to the heavy reduction atmosphere within the enclosed chamber. The pots are left inside this reduction bin until they are cool enough to remove. You can burp the bin which allows some oxygen to re-enter briefly which can cause further changes to the pots surface if there is copper in the glaze used on the pots (reductions reds and greens). Doing this will result in the pots in the bin catching on fire again, so keep faces well back when doing this. You can also quench the somewhat cooled pots in water but caution must be used with this method since the pots are still extremely hot and steam can be released from smaller holes, closed in pots. Experiment, keep notes about the firing and compare results after each firing to see what works for you. 

Raku firing produces some wonderful effects on the clay and glaze. There are some beautiful glaze effects that can be achieved when firing in this way.

I love the whole process involved with Raku firing. It is very exciting, fast and a since it can be a little unpredictable, you never quite know exactly what you will get once you lift the lid of the reduction bin.

Examples of Raku.




Caution: Extreme care must be taken when handling the ceramic fibre blanket used to make such a kiln. Always take the advise of the manufacturer ie. wear appropriate mask and gloves. 

Raku firing is very exciting and rewarding, but can be very dangerous! Great care and safety precautions should be taken into consideration prior to prevent burns and accidents. When Raku Firing, you are handling red hot pots, kilns and equipment, so appropriated clothing and shoes is important. Keep long hair tied back and wear a mask if you think that you may be sensitive to the smoke emitted during post reduction.  Use common sense when working with a group of people to ensure everyone understands the process. If the appropriate safety equipment is used, then you will never have a problem. Always have a hose or buckets of water close by.  I would recommend, that if you are interested and considering raku firing, seek the advice of someone who has fired in this way before and ask to participate in a raku firing to best see how it all works. That is how I learned what I know.


2 comments:

  1. Have you fired your kiln yet? I'm building one. I think, maybe, horizontal is more efficient than vertical, especially because mostly, I'll do tea bowls. Thanks! Lee in Mpls.

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