What’s so great about Raku?
Five years ago I was introduced to Raku. Prior to that, I was content with the vast range of glazes available to me that could transform my pot or sculpture into a finished piece by coating it in a glossy (or matt) sheen. I could even experiment with glazes that would speckle or layer glazes to achieve a multi-coloured finish. Though beautiful, the results were almost always predictable and after a while it was easy to get comfortable with the glazes I worked with. Raku is different. Though you are told what you can expect, you can never get the same result on a glazed piece, nor can you truly predict the colours and flashings (scourge marks) that can emerge when the glaze is reduced (starved of oxygen).
With excited fascination I watched my first Raku pot emerge from the hot kiln (after being sprayed with a copper oxide glaze) and burst into flames as it was placed into a big oil drum filled with wood chippings. More wood chipping were thrown over the top of the pot and the fire grew hotter and more intense. Thinking there was no possible way that any pot could withstand such a brutal assault, I peered on in amazement as the buried pot was then subjected to a shower of cold water that caused it to hiss and ‘clink’ before it was finally removed and placed on the ground in front of me. I have to admit when I first looked at it I was not impressed. It was black and matt and just looked burnt. But I was told to take it to a vat of water and scrub it with steel wool. As the soot came away the colours that emerged were astounding. Turquoise blues and greens (copper in its oxidized state) mixed beautifully with metallic copper flashings where the fire had sucked all the oxygen out of the glaze. There were purples and yellows and silvers that were totally unexpected and I was told it was due to the amount of combustible material around the pot when it was buried in the sawdust. The glaze in certain areas had crazed (tiny cracks had appeared) running like little veins around the pot. The black smoke from the fire had stained the cracks, and all the exposed clay, black. The pot looked like it had been pushed right out of the earth on which we stood and it shimmered in the sunlight. I have been working with Raku ever since! The origins of Raku go back to the 1500s. It is an old traditional Japanese method of firing pottery. The results were highly regarded and finished pieces were used in tea ceremonies and to publicize patrons. Pots were initially fired to low temperatures creating porous surfaces and then coated in lead-based glazes, which were then refired. While the pot was still red-hot, it was removed from the kiln and cooled rapidly with water creating a crackled effect on the glaze. In and of itself, this process produced unique and beautiful items, some of which can still be seen in museums today, but in the mid 20th century the process took a step forward. The glaze was mixed with metal oxides and once the pot had been taken out of the kiln still glowing red, it was introduced to a ‘reduction chamber’. In simple terms, this is an environment (container or area) where the pot interacts with combustible materials such as wood chips or straw. The flames generated lick and envelope the pot drawing oxygen out of the glaze and deoxidising the metal within the glaze.
An example below shows the same glaze: a base white glaze with copper oxide... B) having been exposed to the reduction chamber and A) having been left out of it.
For me the best clay to use for Raku firing is crank clay. This is because it's tough and can withstand the pressure the process puts on the piece. That is not to say you can't use other clays. Experimenting is the key. I mix my own glazes and am constantly learning and trying new recipes to find the perfect 'unusual' glaze. It's a bit like working in a laboratory with lots of chemicals around and, for safety, me masked, gloved and overalled up because some of the chemicals are toxic.
All and all, Raku is a very fiery, hot and dangerous process and I've scorched my eyebrows and lashes at least once! I am always learning and if you are interested in this procedure, get in touch with a ceramic studio and see how great a process this is!