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.
Over the past couple of days a group of us current ceramics students at HDK along with some alumni, have come together to pack the 3.5m square anagama kiln at Nääs along with our smaller wood firing kiln ‘Elinor’. We’ll begin firing early Monday morning, working in shifts of four hours per pair until Wednesday night when the anagama reaches about 1300C. Elinor can be fired to temperature in one day so on the Monday we’ll be feeding two kilns simultaneously.
We began by emptying all our boxes and unwrapping our glazed pots. The anagama needed to be swept out before the kiln could be packed and wadding had to be prepared. The recipes for wadding vary but we used approximately 7 parts Alumina to 3 parts Kaolin (China clay) alongside rye, water and a generous shake of sawdust. This makes up a kind of off-white putty which is rolled into small cocktail sausage shapes that stick all the kiln shelves and supports together. Since the anagama slopes inside, the supports don’t lie flat but are angled on the base and need to be stuck down. Small balls of wadding are spat on and stuck to the base of pots before they’re placed in the kiln. It can be knocked off after the firing but without it the coating of ash through the kiln could stick everything together.
The chun type glazes were placed closer to the back of the kiln because they’re liable to run while glazes that required higher temperatures to melt were put close to the opening where the flame can hit them. Unbisqued work was also put to the back to avoid cracking. This is one of the differences between an anagama and an ordinary wood kiln – in a wood kiln the pots are shielded from the flames while in an anagama they are exposed to them. The temperature is also encouraged to fluctuate in this firing e.g after 1260C we will drop down to 1220, then up to 1270, down to 1240 and so forth to climb steadily, building up lots of layers of ash. We’ll have a pyrometer in the kiln but have also placed eight lots of seven pyrometric cones ranging from 1000C to 1325C in order to measure the temperature difference throughout. These cones are visible in the peep holes down either side of the anagama’s length.
Today we also prepared the daub to seal in the bricks at the kiln’s entrance – 50/50 sand and clay which could be dug up just a few meters away from the kiln, with added water to make a paste. A space for the firebox was kept at the front – here we can push in wood to feed the fire. The base of the entrance is built with alternating columns of soft and hard bricks so that the soft ones can be removed if needed to take out fuel from inside. Around the door too are hard bricks as supports. Some of the bricks at the front had to be sawed and sanded down to make them fit as tightly together as possible.
When packing it’s important to think of how the flames will flow. Like water they will always take the easiest route so it’s good to have a range of heights on each shelf and nothing too large close to the back which could block off flames to the smaller pots in the narrower end. Since we didn’t have quite enough work to fill Elinor, soft bricks were places in the gaps which will keep the air flowing evenly throughout. Generally the packing hasn’t been an especially difficult process, it just takes a lot of time and shuffling things around. Fingers crossed for the next step!
As part of our theory course today where Dominique and I discussed the different approaches to our disciplines in Sweden and the UK, we were visited by Gothenburg based Japanese ceramic artist Masayoshi Oya. He explained that since moving to study in the city years ago, his way of working is a fusion of the aesthetics of the two countries. Oya explained that in Japan functional tableware has a higher status than ‘art objects’, which is radically contrary to the west. Since the times of the samurai the society’s approach has been that the most beauty can be found in objects made for ordinary people.
He also described the difference in how both countries expect an object to be viewed over time. The Japanese concept of wabi sabi as he explained it means pots are glazed with a matte surface so that they pick up marks and scratches with use as they age. These imperfections make them more beautiful. On the other hand, in the west we want our ceramic to stay the same over time, to always look as brand new as the day we bought it.
His comments about time reminded me of the Chiharu Shiota exhibition at Goteborgs konstmuseum in which thousands of individual threads have been stuck together showing that an immense amount of time and effort went into making the installations. Similarly to the wabi sabi aesthetic, time has become tangible. By being able to visualise the time taken ( or the age in the case of wabi sabi) we have a greater respect for the art.
Oya explained that his black stain on porcelain signature decoration is inspired by calligraphy and specifically, calligraphy as approached by someone in the west who is more interested in the way the ink breaks at the edges than creating the lines of a Japanese master calligrapher. He spoke of the way swedes like to stack their tableware and have everything matching whereas in Japan it’s more common to have mismatching vessels to serve food it. Rosa recommended a book called ‘A feast for the eyes: the Japanese art of food arrangement’ which discusses further the relationship between Japanese food and utensils from the Jomon period to the present.
Artist website: http://www.masayoshi-oya.com/
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.
After a conversation with Alice about Italian Still life painter Giorgio Morandi, I went searching for sheets of coloured card on which to experiment with photographing my series of sculptures from the ‘non-spaces’ project. It’s fascinating to see how much the glare from the coloured card effects the objects. The dark blue which is my favourite gives a kind of softness and warmth to the glazes. The yellow is too sharp and harsh while the grey and light blue make everything look washed out.
It’s fun to take the shapes, forms and colours out of the context of the original project. Instead I’m simply working with their material properties in a kind of collage. This method has a lot in common with the work I saw recently at the Moderna Museet in Stockholm about ‘Concretism’. Concrete art ”accustoms man to a direct relationship with things and not with the fiction of things” by rejecting the creation of the illusion of space and three dimension on canvas. Similarly, I don’t want to create an illusion her. I am not interested in conveying any deep meaningful message, I’m only concerned with the balance of form, colour and of positive and negative space.
In other news, I’ve started constructing larger sculptures using repeated press moulded sections in a white molochite stoneware. I’m really excited by the possibilities of working in this way. I like the control over the overall shape from the press mould. It restricts the decisions I can make so I only have to decide where to place them. This new clay is great to work with too – it dries quickly , supporting itself, and so far none of the joins have cracked. I want to see if it’s possible for the shapes to interlock and interact once they have been fired to form one larger piece.
Last week I tried to make my own press mould for the first time, not very successfully. My plan is to create press moulds from composite thrown forms so I can build them together into large sculptures. I find it easier to hand build on a large scale with grogged clay, but it’s painful and not very effective to throw with heavily grogged clay, so I will create press moulds of the thrown objects instead. These forms will be for my final individual project . I’ve narrowed the brief down to explore the imagery of in Italo Calvino’s ‘Invisible Cities’, Ch. Thin Cities 3, especially the idea of a network of pipes as underground veins…
“Whether Armilla is like this because it is unfinished or because it has been demolished, whether the cause is some enchantment or only a whim, I do not know. The fact remains that it has no walls, no ceilings, no floors: it has nothing that makes it seem a city except the water pipes that rise vertically where the houses should be and spread out horizontally where the floors should be: a forest of pipes that end in taps, showers, spouts, overflows. “
I began by bisque firing a form I’d constructed from thrown sections then made a two piece plaster mould of this. The ceramic got stuck in the plaster when I tried to release it, either because I hadn’t used enough soft soap or because I hadn’t placed the middle line in the exact centre.
Since for press moulding it doesn’t matter that the plaster is completely sealed together (unlike slip casting), I used glue to stick the broken plaster pieces together.
This afternoon I’ve been making press moulded shapes ready to start sticking them together tomorrow to build large lattice structures.
Alongside these I’ve been throwing functional ware for the anagama firing we’ll do at Naas in a couple of weeks. These 500g bowls are a little on the heavy side, I’m still a little afraid I’ll turn off too much clay and end up with a hole. I’m been experimenting with the angle and depth of the footrings to see what looks best…