Open fire

The weekend before last I helped Joe Morgan fire his wood kiln, and he very kindly made space for some of my work in the kiln. Last Sunday, after what seemed a painfully long wait, we opened up the kiln.

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Joe lifting the lid, underneath you can just see kiln fibre and kiln shelves covering the ware chambers.

The wood/soda firing process is very different from what I know. It took me a while to get my head around the approach required… using a different clay, glazing only the inside of pieces, using oxide slips to work with the soda to create the characteristic glaze that comes with soda firing. Even though all the pieces I made are essentially tests it was hard not to be very excited to find out how they had come out.

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Kitty and Joe Morgan lifting the final kiln shelves to reveal the pots inside.
You can see Joe’s amazing teapots and some of Hilary Firth’s plates and jars.

As we had thought the first stack had fired well, but the other two did not reach the required temperature. That said the firing was better than the previous one – it takes time to bed in a new kiln and Joe has plans to make a few modifications before the next firing.

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Some of the slip combinations and decoration I tried worked quite well, the glaze liner didn’t go as glassy as I had hoped, and I think I threw things too finely as many pieces warped. I’ve learned a lot and have lots of ideas to take forward. Now I just need to make some more pots.

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This carafe was right at the front by the fire box so it got very hot.
It also welded itself to the kiln shelf, but there are some beautiful colours here.
The inside and rim has a celadon glaze, but there was just bare clay on the outside.
This is where the soda and wood ash have created their own magic.
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This is perhaps my favorite piece from this firing, decorated in a copper/cobalt slip, with a celadon liner.
Where the soda has hit with full intensity it has created the strong blue glaze.
You can clearly see the other areas that received less soda.
These are more metallic in nature from the copper in the slip.

With huge thanks to Joe Morgan for such an amazing experience, and to Hilary Firth, Joseph Travis and Robin Palmer for such good company.

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Fire on

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Last weekend I had the great pleasure of helping Joe Morgan with the third firing of his new wood/soda kiln. I helped a little with its second firing at the end of last year.

Joe, Joseph Travis and Hilary Firth packed the kiln on the Saturday, then we fired on the Sunday. I arrived at 6.30am and the boys had already got going. I’m a novice at wood firing but I’ll try to explain a little of the process involved…

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The kiln is based on the ‘long’ kilns that Sandra Lockwood and Steve Harrison use in Australia. The fire box is of bourry box design, the chamber long and low. To start, a small fire is lit on the firebox floor using small pieces of kindling. It is imperative to slowly increase the temperature until the kiln has passed all the ‘danger’ points. Pour water at 100˚C, chemically combined water at around 350˚C and lastly quartz inversion at 573˚C. Over the next few hours the fire is built up increasing the embers in the ash pit until around 600˚C is reached on the pyrometer. At this point we switch from adding small pieces of wood through the front to much larger/longer pieces onto the upper part of the bourry box. These rest on hobs over the ash pit and allow the kiln to draw the heat and flames down through the kiln. The rate of draw and atmosphere can be adjusted by adjusting the primary and secondary air holes at the front of the kiln and dampers in the chimney. 

It is continual work to keep the fire fed… sawing, chopping and splitting wood to the right size; feeding and maintaining the fire; monitoring temperature and so on. It is intoxicating though – such a medieval process, involving proper graft, but massively exciting and hopefully rewarding. It is particularly enjoyable when with others… the chat and company spurs everyone on.

The temperature in the kiln’s chambers is checked firstly by using a pyrometer. In addition to this draw rings made from terracotta and stoneware are removed at various points to monitor the atmosphere in the kiln. Pyrometric cones are also observed through spy holes to check the progress in each of the ware chambers.

Once cone 10 goes down (1300˚C) in the first chamber (closest to the firebox) we introduce soda via bark ‘canoes’. These are carefully added to the firebox – the sizzle of the soda vaporising is a very welcome sound. The sodium vapour is then carried through the kiln with the flames and combines with silica in the clay. This will hopefully create the characteristic dimpled ‘orange peel’ glaze associated with soda firing. The last of the wood is added to the firebox before closing down the front of the kiln. Then side stoking begins through four small holes on either side of the kiln. These are located between the three ware chambers. Long, thin pieces of wood are carefully introduced to continue feeding the fire, all the while ensuring that they don’t touch the pots on either side. Finally more soda, wrapped in paper parcels are introduced through the four side stokes before the firing is completed.

By this time it was 9pm and we were exhilarated, but shattered. The firing was better than last time, but we won’t be sure of the results until we open up the kiln next weekend.

As we were tidying up in the darkness, we witnessed the perfect finale for our day’s labour… the most fantastic display of the Northern Lights. Breathtaking.

With many thanks to Joe Morgan, for help with the technical details.

Naked

I mentioned in my previous post that David Roberts kindly let us bring some pieces to raku fire during our SPA weekend at Kindrogan. I’ve done naked raku once before, at Gray’s School of Art, and I’ve been meaning to have another go. This experience has inspired me to try and do further firings at home, perhaps over the summer.

David is a master of raku ceramics. His large-scale pieces are breathtaking and it was fascinating to discover more about his process. He cleverly juxtaposes rough and smooth surfaces in his pieces which adds depth to his already complex designs.

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A detail of one of David’s stunning large bowls.

We were asked to bring some already bisque fired pieces to the workshop. Ideally these would be burnished to a smooth finish or have terra sigillata applied. The pieces were dipped into a barrier slip, some with areas already masked off. Once dry they were dipped into a raku glaze and dried again. At this point they could be fired as they were, or designs could be incised through the layers of glaze and slip. The slip is what stops the glaze from adhering to the pot during firing. The areas that have been left bare will become black during reduction.

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First the pieces were gas fired relatively quickly to approximately 850˚C. 

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The pieces were pulled from the kilns and put into reduction chambers.

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Then they were taken out and the glaze chipped away to reveal the naked pot underneath. 

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Following a good scrub to remove any remaining slip the pots were allowed to dry.
I almost love the bases more than the tops.

Reflecting

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After yesterday’s biscuit firing I washed everything today, ready for glazing*. During this process I had a chance for a moment’s contemplation as this is the first time in a while that I’ve noticed a significant improvement in my throwing. The pieces feel lighter and more consistent in thickness… some real progress. Recently someone gave me some advice about throwing with softer clay for wider pieces such as plates and this has been really helpful.

As I have mentioned before, with potting there always seems to some kind of humbling element just to keep you in check. With this firing I have been reminded that rushing things is never a good idea… We will be without electricity early next week so I knew I needed to get a biscuit firing and one glaze firing done before then. I over packed the kiln and some pieces were not as dry as they should have been. I thought I had allowed for this by adding some preheat time to the already slow firing schedule… well I suppose that two breakages out of a total 77 pots isn’t too bad. Here’s hoping the survivors make it through their glaze firings ready for Ministry of Craft on 6 December.

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I must say that although I am really enjoying progressing my existing work I sometimes find it difficult to resist the urge to develop new ideas. I’ve got page after page of sketches that I’m itching to try out… I’m looking forward to experimenting in the New Year, when hopefully things will be a little quieter.

*It is important to brush, sponge or wash off of any dust from the first firing to ensure glaze adheres well. Also before washing I like to sand the bases and rims to remove any rough spots.

Open fire

During the open studios last week I did a couple of raku demonstrations using my homemade dustbin kiln and I had some lovely visitors to witness the process. Thank you to Hilary Firth from Starglazing for taking most of the following photographs…

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Kiln heating up nicely, using a probe to keep an eye on the temperature.

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Once the kiln reaches temperature and the glaze has matured,
the lid is removed and red hot pieces are removed with tongs.

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Red hot pieces are placed into a reduction (smoking) chamber lined with sawdust.
The lid is put on and the chamber is left until it has cooled.

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A blackened piece after being removed from the reduction chamber.

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The blackened pieces are then scrubbed under water.

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The best of the bunch with some great copper flashing.

The transformation the urchins undergo is fascinating to me. These blackened lumps are removed and are scrubbed until they reveal their true selves, just like treasure from a wreck being brought to the surface, cleaned and discovered,

Someone mentioned to me a while ago that I should try using less sawdust for the reduction and this advice worked a treat. In fact the results were the best ever. I’ve been trying to replicate one particular piece that I fired during my course at Gray’s and this was the first time I’ve managed that. So, after five raku firings I am by no means an expert, but progress is definitely being made.

Smoke pot

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Sea urchin; straight from reduction (smoke) chamber (l) and after cleaning (r)

I thought I wouldn’t make it into the studio until next week but I got itchy fingers yesterday and couldn’t resist. I didn’t have time to throw anything so I decided to do some raku glazing and firing instead. It looked like it would be a perfect clear cold night for my second firing using the homemade kiln. I mixed up a new version of the turquoise raku glaze that I have used before – this time with a little less copper oxide in the hope for a lighter colour. I glazed a number of small urchins that were biscuit fired before the holidays. After trying to learn from my previous mistakes the results were much better than last time: a much quicker firing; and a better glaze colour; but nearly everything cracked again. Now I’m sure I need to change to a clay with more grog in it.

What I do love about raku firing is that at first you pull out these black lumps from the reduction chamber and they look pretty grim, but then you get them under the tap and start to scrub away the soot and smoke to reveal the finished pot beneath.

Next time I must remember some marshmallows for toasting.

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