Raku Firing Wednesday Workshop

In addition to the Tuesday workshop we can choose to sign up for various other open workshops. For the first three weeks I have designed to learn the skill of Raku firing as it is something I am interested in and is something I would like to explore to go along with my new found interest in ceramics.

We began by making some pieces to be Raku fired, using a special Raku clay which has a high grog content making it quite painful to throw with on the wheel but less fragile. I made three pots, two of which I quite like and one which didn’t quite work due to a last minuet accident and I wasn’t entirely successful in recovering it. Unfortunately, I also missed the firing for our Raku clay firing, so I decided to used some Whites St Thomas bisque fired clay pieced that I had happened to fire last term and I could use for the Raku process.

Next we had to apply the glaze. How we applied the glaze depended on the glaze itself. There are a wide range of Raku glazes that we could choose from, each giving a different effects. Most of them you could simply dip or spray, and pour the inside of you vessel, however to achieve some interesting effects, some more work was needed; I wanted to use a glaze whereby you needed to apply 4 coats of slip followed by 4 coats of glaze. This meant that when you Raku fired the piece the glazed would actually peel off to reveal the slip below with the cracks of the glazed impregnated into it, finishing the pot in a matt finish, with black crack pattern and smoke dots covering the surface.

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Once this was complete we began the firing process the following week. This is a really exciting and interesting process. It involves rapidly firing your pots up to 1000 degrees over a time period of about 30 minutes, in a gas kiln. When the pots have reached temperature the glaze will become reflective so you can tell their temperature by inserting a metal rod into the kiln and if the pots reflect the rod they are hot enough. You then take them out of the kiln red hot and place them into a bin of sawdust and cover them in further sawdust which burns immediately so you need to be fairly swift to place all your work from the kiln into the bin covering it in a sawdust and then cover the top starving it of oxygen to burn so all you get is dense thick smoke inside the bin. You then put the bin in the smoke chamber for about 20 minutes. What happens to your pots is highly unpredictable and dependant on what glaze you use. Most glazes will crack due to the rapid heat change and when they are smoked the smoke will become trapped in those cracks defining those cracks, giving a nice crackled surface to the pots. It get interesting when you use copper elements in the glaze as it will oxidise and bring forth many different colours such as metal bronzes reds, greens, deep blues, and is once again highly unpredictable how it will look.

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My pot which I applied a slip and then glaze to turned out really nicely. The crack formed a pattern on the pot which I could have never scratched into the pot and a random array of large dots to go along side these cracks. The matt finish looked really good as well and contrasted really well with the inside of the pot which was blue and, due to a small amount of copper content, had oxidized further down inside the pot to give a really nice effect. I wasn’t as pleased with the other pot, which didn’t turn out as expected, with the white glaze bubbling up quite a bit in places and then turning very metallic in other places. But I think the biggest fail was the top which just turned a brown earthy colour. Some may like the effect but I didn’t. However, that is what I love about this process is how unpredictable it is and how it is pretty much entirely down the pot and the glaze and what happens in the kiln and in the smoke chamber. I think it amazing that the piece of work basically creates itself, the maker simply create a platform, a clean canvas for the Raku process to work its magic!


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(peeling the glaze away from the pot)






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