Hands up everyone who want to try out raku firing from seeing it on ‘The Great Pottery Throw Down’ the other week! Here at Pavilion Craft HQ it certainly made us itching for attempting our own raku-fired sake sets. It’s not a technique for the faint-hearted – the risk of pieces exploding or cracking is high, and the results of glazing are unpredictable. But when it works, it produces beautiful results. Raku pieces are traditionally shaped by hand rather than being thrown, and are usually decorative. The word ‘raku’ derives from a Japanese expression meaning enjoyment or happiness. Read on to find out more about this fascinating firing process.
A crackled or crazed finish is characteristic of raku ware. Here a thin-necked vase is carefully lifted out of the fire using tongs.
Chaotic, elemental, volatile: raku is one of the most spectacular, dangerous and technically demanding of all ceramics techniques. Glazed pieces are fired for a short time at a high temperature in a raku kiln, which is smaller than a regular kiln and pyramid shaped. They are removed from the kiln when they are red hot and then either left to cool in the air, covered in combustible material in a ‘reduction chamber’ or plunged into water. There is nothing gentle about the process whatsoever – steam hisses, smoke billows and sparks literally fly. The risk of pieces exploding or cracking is high, and the results of glazing are unpredictable. It is truly a high-wire act for experienced potters and novices alike.
‘Steam hisses, smoke billows and sparks literally fly’
The raku style, originating in the sixteenth century, was a significant development in Japanese pottery. From that period onwards, modest hand-shaped chawan tea bowls, often crackle-glazed in subdued colours, became an important component of the tea ceremony.
Raku-fired pots, such as this simple tea bowl, are a key element of the traditional Japanese tea ceremony.
The British studio potter Bernard Leach (1887–1979) brought his own version of the tradition to the West, installing a wood-fired Japanese kiln at his St Ives pottery in 1922. Since then, many potters around the world have experimented with the technique, notably the celebrated American ceramics artist Paul Soldner (1921–2011), who said: ‘In the spirit of raku, there is the necessity to embrace the element of surprise. There can be no fear of losing what was once planned and there must be an urge to grow along with the discovery of the unknown.’ The use of a reduction chamber after firing was Soldner’s innovation.
Clays used for raku must be able to withstand immense thermal shock. To increase resilience to violent temperature changes, ‘grog’, or some other form of temper, is added to the basic clay. (Grog is clay that has already been fired, then ground down to a powder.) After throwing or shaping, forms are left to dry and then bisque fired, the timings determined by their size and mass.
Raku lends itself to experimenting with masking out. Patterns, lines and shapes can be created during the glazing process by covering sections with wax or tape that will burn off in the firing, leaving the clay body exposed. Wax is useful for creating curves, while tape gives a more linear effect. Glazes need to be applied relatively thickly for the best results.
‘A perilous process requiring nerves of steel, steady hands, long tongs and protective clothing to negotiate safely’
The final stage is where the unpredictability and drama comes in. After an hour or two of final glaze firing at a high temperature – around 1000°C (1830°F) – the forms are removed from the kiln while they are still red hot, in itself a perilous process requiring nerves of steel, steady hands, long tongs and protective clothing to negotiate safely.
What happens next depends on how the pieces are subsequently treated. In traditional Japanese raku firing, the final stage is to cool the forms slowly in the open air. Cooling them quickly, by plunging them into water, produces different chemical reactions in the glazes, instantly fixing them and giving much more vibrant colour effects, but at the greater risk of ruinous cracking and shattering.
Alternatively, fired pieces can be removed from the kiln and dropped into the potential inferno of a ‘reduction chamber’, typically a metal dustbin filled with some form of combustible material, such as sawdust – although one enterprising ‘Throw Down’ contestant used a mixture of dried gorse, bladderwrack and manure. The bin is then covered with a lid, which can be sealed with clay around its rim to make it more airtight. The heat from the fired pieces sets the combustible material alight and, as it continues to burn, oxygen in the chamber is reduced until it is pulled directly from the glazes and clay. After the charred debris has been cleaned away and the scrubbing process has been completed, any unglazed areas will emerge black, while glazes will have an iridescent sheen. Crackled or crazed finishes can be achieved by leaving the piece in the open air before the reduction process.
Extracted from The Great Pottery Throw Down by Liz Wilhide and Susie Hodge. Out now!
Raku tea bowl picture by Joanne Moyes/Ceramics John Moyes.