Calcium Carbonate (Whiting) 14
Potash Feldspar 35
Iron Oxide 0.52
Bone ash (Benaska) 2
Soda Ash 8.1
Nepheline Syenite 39.3
Ball clay 17.2
Celadon recipe here
Calcium Carbonate (Whiting) 14
Potash Feldspar 35
Iron Oxide 0.52
Bone ash (Benaska) 2
Soda Ash 8.1
Nepheline Syenite 39.3
Ball clay 17.2
Celadon recipe here
The past three days have been spent at HDK’s kiln site at Nääs where we fired both the anagama (Mamagama) and Elinor (the smaller wood kiln).
Since Elin and I were scheduled for the first shift on Monday morning, we arrived on site around 6am and started up the anagama. We pulled out the bricks from the central air hole at the base and built a small brick box in which we set fire to some newspaper and placed dry kindling on top. We began by taking the temperature up at a slow pace, 25C per hour until reaching 100C, with the fire still mainly in the box outside the kiln. As a temperature gauge we used a pyrometer stuck through a crack in the door but later decided to place it in a hole in the kiln’s roof to get a more accurate reading of the inside temperature. We sealed the door with the daub we made last week, blocking out the bumble bee who was desperate to get inside despite the rising heat!
After four hours we let another pair take over and we worked this way in shifts of four hours per team for the entire firing. Around 10am Elinor was started and taken up to temperature at a much faster rate. Reduction in Elinor took place on Monday afternoon when the kiln had reached 1000C. Creating a reduction atmosphere before this temperature means the clay can get reduced instead of the glazes which can cause it to trap carbon and turn a very dark colour which might be undesirable.
Sometimes when too many logs were fed in too quickly, black smoke started spewing out the chimney – a sign reduction was taking place, and we had to be more patient. It’s difficult to get the balance between allowing in enough oxygen for the flames and allowing in too much which starts the reduction process because the cold air blocks the flow.
When feeding logs into the kilns the temperature would fluctuate up and down a lot, sometimes peaking three times before finally decreasing for good. We were told to focus on the fire and not rely on the pyrometer though. It’s possible to hear when the kiln is ‘hungry’ again because the fire goes quiet and the crackling stops. We also used pyrometric cones placed at the front, middle and back of the kilns to check temperature. When the cones were bending unevenly e.g. if on the left side there were four standing and on the right five, we put in less wood and slowed down the temperature gain. Another way to check if the glazes are melting is to poke a stick in through one of the anagama’s peep holes and see if the pot’s surface is shiny enough to reflect off it, a technique I’ve used before when firing raku.
It’s important to make sure that the last logs have turned into embers before more have been added. Unless you do this you find yourself in a situation like we did early on Wednesday morning when the anagama would refuse to climb above 1220C. Looking into the airholes we realised that the embers were so high that they were blocking the oxygen flow into the kiln so the fire couldn’t grow. By pulling out logs and moving around the embers inside we fixed the problem, but the temperature dropped dramatically so we worried that we would be behind schedule. This could be fixed though by filling the door with long thin sticks sticking into the flames which raised the temperature.
In between shifts we took turns breaking down the logs with a hydraulic wood splitter and cutting some down even smaller with an axe. Smaller pieces of wood raise the temperature because they burn quicker but it’s best to use a mixture of thick and thin, long and short logs to get an even rise. When stoking the kiln, sometimes we would place two small logs crossed in the doorway to conserve heat.
Our fifth and final shift started at 6pm on Wednesday night. We kept the temperature around 1250C until 7pm when we topped at 1300C before bringing it back down to 1270C. We topped another 5 or so times before filling the kiln with as many long sticks as possible and sealing as many holes as possible in turns. This was probably the most stressful part of the firing because it needs to be done fast and the kiln is at its hottest. It was impossible to feed in logs for very long because your legs feel like they’re burning! It was necessary to wear welding goggles, scarves over our hair and mouths, long sleeves to cover arms and legs, sturdy boots and flameproof gloves. After sealing the gaps in the kiln with daub, cold water was poured all around the kiln to make sure none of the logs piled around it would catch fire once we left.
I felt my heart sink when I went to open the kiln this morning. Instead of a rainbow of bright colours – lime greens, turquoises, salmon pinks and cobalt blue, I found my series of white earthenware thrown plates had all turned a yellowish off-white. Checking back over the glazes I’d used I realised I’d made some mistakes with the calculations when I tried to double the ingredients. I’d added 1% of coloured stain to the new glazes instead of 10% to the base glaze.
I should have realised something was off by the pale colour of the glazes in liquid form. I was hoping to display these colour experiments on the wall for next week’s corridor exhibition but I’ll have to think of something else instead. The firing itself didn’t really go to plan either. The first time I though I’d put the kiln on, I came back in the morning to find the kiln still on 50C. I hadn’t pressed and held the start button down to begin the program!
Hopefully I’ve learnt a lesson to keep neater notebooks so I’m not cramming illegible glaze recipes into every area of free blank space.
Renata held a fun glaze workshop with us in which we made a glaze based on our date of birth. We randomly chose glaze materials to mix in proportion to the year, month and day we were born. By comparing each other’s glazes we could get a good idea of how each material behaves when fired.
My glaze was the result of mixing a high proportion of whiting with some dolomite and ball clay and a small amount of Wood ash. Fired to stoneware temperature the result is a very dry, matte and slightly flaky off -white/pale green glaze blending into pink lower down in a gradient effect. The ash has pooled in a shiny green line along the base where it has melted. It’s not suitable for functional ware because it hasn’t fully melted, but I’m excited to use it to decorate sculptural forms.
Whiting (calcium carbonate) acts as a flux and also creates matte effects (as does dolomite). Ball clay is a source of alumina and enhances glaze suspension. I want to make a series of glaze tests using the same four ingredients but changing their percentages so that I can get a better glaze fit.
UPDATE: After a couple of months the glaze has flaked off completely
Just back from a magical few days volunteering (for the first time) at the 23rd Art in Clay on the grounds of Hatfield House. This was a great opportunity to meet makers of all sorts of styles and techniques and learn more about their work, while at the same time learning how to display work for sale and interact with the public. Saturday night’s BBQ was a highlight and it was great to meet like-minded ceramics students from Farnham. Definitely one for next year’s calendar!
Another of the show’s highlights for me was Matthew Blakely’s talk about sourcing the rocks and materials he uses for his glazes. Seeing the vibrant range of effects he could get with as little as wood ash and clay has inspired me to start sourcing my own glaze materials from places I travel as well as my local area. He described how he uses a ball mill to grind down materials and how some rocks (like granite) will become soft when heated in a kiln while flint is dangerous because it will explode. He also spoke of the importance of getting permission to gather materials from the landscape, especially when selling the work afterwards, and of taking photos of where the natural rocks, clays and ashes were sourced. I agree with the audience members it would be great to see the finished pots photographed in the landscape they are linked to, like Adam Buick does. Matthew explained how buyers would receive a CD with their pot with information about how it was made.
It was insightful to see how different potters wrapped theirs work too, some using bubble wrap, newspaper, brown paper and elastic bands…some having to use round boxes with lots of sponge for fragile work.
Melissa Pritchard runs Parade Mews pottery in South London and creates stunning soda fired pots. Some of the glazes shimmer like fish scales.
Kathrin Najorka’s wood and salt-fired stoneware (above) is modest and homely, effectively displayed on these dark wooden shelves to make them look even more rustic. I really admired her work as well as the porcelain and stoneware thrown tableware of another German artist – Susanne Lukas-Ringel. I’d like to learn more about firing in these alternative ways to an electric kiln.
As I mentioned in a previous post I find myself drawn to works made in a black clay body with surface decoration in white. Naturally, I got really excited when I saw Margaret Curtis‘s work! She began using black clay after visiting the studio of Japanese potter Miwa Kyusetsu X1 and admiring the crawling snow-white shino glazes on the black clay body of his tea bowls (chawan). She achieves crusting white textures with thick porcelain slip.
Tim Lake is a potter based in Carmarthenshire who makes eastern inspired pots, bowls and tea bowls, all on a kickwheel. I was drawn to the natural, muted colours of the glazes and impressed decoration.
Surprisingly though, my favourite piece in the whole show was not a ‘pot’ in the traditional sense at all, but this adorable ‘little ugly being’ by Chiu-i-wu. It’s a fat little creature with sharp teeth that clearly just wants to be loved! Her work is hand-built and she draws influences from her love of English summers as well as her home country Taiwan. Her forms remind me of illustrations in children’s books and this dry, green surface makes me think of the oxidation you get on copper roofs.
I feel this year I’ve focused (although not as much as I could have) on improving my throwing skills. It’s a process I enjoy, but rather than viewing it as a means to an end, I see it as more as a starting point for the process of construction, much like artists Wouter Dam, Carina Ciscato and Walter Keeler.
I began the first project ‘Many a Slip’ trying to repeat throw a particular form – that of a distinctively shaped mug I remembered from home. I discovered though, when I found a picture of the actual mug, that my memory of the object was distorted, a caricature of a mug. This made me think of how unreliable memory is and blind drawing exercises in the New Materialisms Constellation study group explored these ideas of how we perceive with our senses further. This idea of memory and trace fed into the ‘Cafe Society’ project. My cafe was to be a piece of home in Cardiff, somewhere I could go to escape the busy city and feel I was back in the wild, mountainous landscape of North Wales. The layout of the place would be similar to my favourite coffee shop in Dolgellau – T.H.Roberts, the old ironmongers, the top floor kitted out with second hand sofas, and they would serve the local speciality – Popty’r Dre’s honey buns.
I made a series of my ‘home’ mugs which I hope to saggar fire tomorrow with combustibles sourced from the Dolgellau area – seaweed and shells from Barmouth beach and sheep wool and lichen from the farmers fields on the foot of Cader Idris. I want the surfaces of the mugs to show a physical trace of my home. The project has made me think of the things I take for granted and how your memory of a place can change when you move away and grow older. It makes me think of Malcolm Pryce’s Aberystwyth Noir novel series – about an alternative underworld Aberystwyth which he only began to write about when he moved away from the place.
With the handbuilding of thrown forms I find myself returning to the theme of balance, which happened to be what I wrote my final Constellation essay about. I find my making process if becoming more and more process driven rather than schematic and pre-planned. I find I like to play with the material and discover ways sections want to fit together harmoniously and naturally rather than trying to bring a drawing or plan into being. This thinking has definitely been influenced by learning about ideas of the agency of materials in Constellation. I feel as a result though that I’ve abandoned research a bit and work in sketchbooks less than I used to.
I noticed this change of thinking most when I came to the final ‘Centrepiece’ project and originally wanted to make an interactive piece or a game, but realised I didn’t want to work to a plan. It’s also becoming more and more important to me that what I make shows a trace of how it’s been made. This is why I like the flow of throwing lines and marks where the fire has licked the clay in kilns that aren’t electric fired. I hope to move away from the standard oxidation electric kiln firings next year. I’d especially to learn how to use the gas kilns for reduction firings and look more in depth at alternative firing methods like raku, saggar and wood firing. I liked the unexpected, uneven results and surface textures you get this way, like the ones on my final centrepiece.
Looking through my blog I feel it would help to post a summary of my developing ideas at the end of each week next year so I can see a more clear progression. Also I’d like to upload films of myself working so I can more dynamically document the skills and techniques I’m learning.
Inspired by the pit firing on the Pottery throw down, Nina, Nam and I tried our own smoke firing over Easter with the help of the fabulous Ian Hinchliffe, potter at Quarry Pottery in Corris Craft Centre. We took a similar approach to the oil lamp bin firing Mick Morgan helped us with before the holidays – lining a bin with newspaper then dried wood chopped down as kindling.
The pots were wrapped in copper and steel wire then generously sprinkled with copper carbonate, cobalt oxide, black nickel oxide and a mixture of blue, yellow and pink commercial stains. Dried ferns, pine needles, leaves and banana skin were also added before they were wrapped up in tin foil. Once surrounded by the kindling we set the bin alight though the holes in the bottom and kept adding wood for a good few hours, the metal gradually turning red hot.
More stains, salt and oxides were sprinkled on during the evening, which, if they didn’t make much impact on the surface colours, definitely made for some spectacular electric blue coloured flames for us to watch. The experience of sitting around a fire with a group of people as darkness gently fell over the welsh hills, our shared hopes invested in our kiln babies and mesmerised by the flickering light and warmth of the flames, was an unforgettable experience. The raw power of the flames made me feel connected to something primal. I suppose our early ancestors would have felt the same awe sat around their bonfires at night. Although perhaps it’s just that every potter is a bit of a pyromaniac.
Opening the kiln in the morning, we were surprised to find all the foil burnt away but the pots hadn’t turned as dark as we expected. The colours came out best on the slipcast porcelain vessels with striking flushes of pink and constellations of smokey greys and browns on their smooth surfaces. Burnishing the pots beforehand would have improved the surface quality and leaving them in a reduction atmosphere for longer may have turned the surface darker.