Kiln Building with Joe Finch

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DAY 1

I spent the weekend at the home of jeweller and ceramic artist Linda Unsworth (Pampeliska) in the Preselli hills where a group of us had got together under the leadership of potter and expert kiln builder Joe Finch to build Linda a small wood kiln in the garden.

We began with a flat concrete base into which holes had been drilled to let the moisture escape. It’s also possible to build onto a base of hollow concrete blocks with insluating blanket over the top. Firebricks had been laid out on top of the concrete in the shape of the kiln’s base and we built up onto this one layer at a time, photographing each layer. On the outer brick layer were light insulating bricks and heavier firebricks on the inside wall against where the flames will be. The chimney was built in a more aesthetic red reclaimed firebrick.

Joe’s kiln design is five bricks across and four wide and he’d built a model from Lego to guide us. Joe advises working out the size of the kiln you want after deciding how many kiln shelves you want to fit inside. The two chambers either side are fireboxes into which the wood will be fed through two openings at the front creating a ‘fast fire’ down draft style of kiln – the chamber in the middle will pull the flames back down and out the chimney. You can see in the photo that the second layer of bricks is pushed out slightly in the firebox to create a ledge. This is for the perforated brick layer to sit on. The idea is that the embers from the logs burning on the firebars above will drop down onto these and the oxygen through the holes will help combust them, meaning you don’t have to rake out the embers so often like in other kilns. In the chimney you can see a space where the bricks are missing – this is where the damper will be placed and bricks can be pulled out here to create reduction.

As the kiln got taller we added the firebars – hollow tubes of refractory fireclay onto which the logs will be placed. These need to be loose enough so they can be pulled out and replaced if needed. We continued to build up the bricks layer by layer, insulating on the outside and firebricks on the inside, sometimes having to saw bricks in half to fill in cracks and filling smaller gaps with gaskets of insulating ceramic fibre. Things became more complicated when we began the kiln chamber floor. We placed the flattest kiln shelves we could find on top of the fireboxes, leaving two gaps for the back for the flames to flow through and one at the front in the middle. We covered the flue to the chimney too.

Things picked up after this stage when the job got easier – we simply built the insulating bricks up in layers around the perimeter of the kiln chamber. Once the desired height was reached (about 2m high for the entire kiln) Linda painted numbers on the bricks that will make up the door using watered down red iron oxide. Joe then sawed out the door.

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DAY 2

We began Sunday morning by mixing up a mortar for the reclaimed molar bricks for the outside kiln cladding. This second layer of insulating bricks isn’t necessary but makes the kiln look more aesthetic. As a cheaper alternative it’s possible to cover the inner layer of bricks in insulating fibre then add a corrugated iron shell.

The mortar was a mixture of ball clay, sand, water and red iron oxide (the iron colours the mixture pink so it blends in better with the red bricks). The bricks were each soaked in water for a few seconds before building with so they absorbed the mortar better. Since the bricks were reclaimed we spent some time scraping the layer of old mortar off the surfaces before we could begin the next stage.

The cone spyholes in the back had to be adjusted for this second layer of bricks so we made new longer ones which can be pushed in at an angle. After completing one wall of outer layer we added the supporting angle irons on the outer corners and secured these together with a 12mm threaded rod (could use 5mm), then slid in horizontal ones between them.

The roof was constructed with three layers of insulating bricks cut at angles to make an arch. A D shaped wooden arc support frame was held up by planks underneath and we built the arches over the top, supported either side by bricks cut in half length-ways. Once the other outer walls have been completed the frame should be able to drop and slide out through the kiln entrance leaving a freestanding roof. Unfortunately by the end of the weekend we’d run out of the reclaimed bricks so we couldn’t complete the outer layer fully but Linda has promised to send photos of the finished kiln – I’m looking forward to see the results! More information about kiln building can be found in Joe’s book ‘Kiln Construction: A Brick by Brick Approach’.

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Birthday Glaze

20180209_161019 (600x800).jpgRenata 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

 

 

The Body and the Vessel: Workshop with Matilda Haggärde

Yesterday we took part in a workshop held by HDK graduate Matilda Haggärde who currently works with dancers and the Gothenburg opera to explore the potential of clay in performance. She began by speaking about her own background and her performance piece in which she builds coils of clay around herself until she is enclosed in a pot, which she then breaks open and emerges from, like a butterfly from a cocoon. Although it’s a simple idea, the action evokes many metaphors. It also reminded me of a workshop I took part in years ago with an artist called Zoe Robertson who creates monumental jewellery and objects to be explored through movement and the body.

jj (700x720)Next we took part in a ‘body scan’ exercise where we all closed our eyes and Matilda took us through a kind of guided meditation but with the aim in mind of feeling where our bodies held tension or felt heavy. During this exercise I became very conscious of the hardness of my spine against the flat surface of the chair and kept having to shuffle to feel comfortable. I began to think about how the softness and delicacy of our skin juxtaposes the strength and harness of our bones, and also of the skin as a kind of stretchy container for these hard objects.  I wasn’t sure how to express this in clay so I began with a large scale charcoal drawing, trying to stretch the lines over imagined shapes.

The forms I drew felt visceral and grotesque – I realised I was thinking more and more about what lay underneath the skin, the blood vessels, intestines and internal organs. The final drawing looks like some organic system or machine. I also noticed as I worked into my drawings that they seemed to sprout tumours or cysts. Being prone to develop benign skin cysts myself, I am somewhat fascinated and at the same time repulsed by these strange growths. They are somehow of the body yet not connected to it in any way, similar to how when you are pregnant, your baby is at once part of your body but also a completely separate being.

I began to build on top of the drawing by pressing coils into my hand to try and lift some imprint of its creases and link them together in a way inspired by the technique ceramicist Claire Curneen uses, with tiny gaps in-between suggesting the fragility of the skin. I also began overlapping sections of clay to create the impression of plates of armour, thinking about the protection the skin gives to all that is inside. When I became bored of this making technique I reverted back to the charcoal, drawing the clay shape I made. The idea was to try a ‘ping-pong’ method of making like artist Kate Haywood uses – going back and forth between drawing and sculpting to see how one can influence the other. I like my drawing much more than the effect of the clay on top which just looks flat and fiddly. Transposing it up to a much larger scale would feel more ‘of the body’ because the space the body occupies would be mirrored in the space the clay occupies. The drawing from the clay just looks a bit like a phantom duck!

Enamelling

In a similar way to how glaze powder is fused into glass on ceramic, enamel powders are fused onto copper. The temperature however is a lot lower, any higher than 800C and the enamel starts to discolour, as I soon found out.
Before and after shaping the copper needs annealing and then plunging in cold water to cool. Gum arabic is painted onto the back of the shape after cleaning, then backing enamel is dusted on top and the copper placed in a small kiln. When opened the kiln temperature plunges and you have to keep an eye on it as it gradually climbs back up to 799C. On the opposite surface different coloured enamels are fused on in separate firings, although the process is a bit more difficult than I expected. The colours don’t behave as planned, burning out before the kiln reaches optimum temperature or leaving speckled textures (which can look nice – a bit like a dusting of snow).
I’d like to know if these copper enamels can be used on top of bisqued or glazed clay. Alternatively, perhaps panels of enamelled copper (maybe a maker’s mark) could be inlaid into the clay after firing by being stuck on, although I’d have to contest with shrinkage.

 

Hot melt rubber molds

I took part in my first ‘open house’ workshop today where I learnt how to use the hot melt vinyl compound Vinamold/Gelflex to make flexible moulds. Much cheaper than silicone, it can be used to cast all sorts, from plaster to wax, resins and ceramic material.However it does have some drawbacks, namely that it shrinks over time and when used with plaster or wood they have to be soaked first in water.

The Vinamold is first cut into sugar-cube sized chunks which is a bit of a challenge but is easiest done with a stanley knife and scissors. The texture is similar to that of tough meat. Next it’s heated in the microwave to around 150C which took around 6 minutes for  a full Pyrex measuring jug, a little longer for larger quantities. It’s best to check the consistency every 3 minutes or so in case it begins to burn. The objects we wanted to make moulds of were placed onto sheets of clay with a cottle to give a gap of about two fingers width in between. When the compound was of a runny, soupy consistency it was poured into the moulds and left to set for about an hour. It was easy to release the objects from inside and every tiny detail is captured. The process is so much quicker than making a plaster mould.

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