There are different types of firings that can be used in pottery.
The first firing is called bisquit. It serves to transform the clay in pottery, making it hard permanently. Generally rises to 800/900 °C for a minimum of eight hours. The second firing - or glaze firing - is done at a higher temperature than the bisquit, ranging from 1.000 to 1.300 °C.
There are also other widespread techniques:
Single firing: the method in which the piece (still raw) go just once to the oven, with the glaze already applied. This type of firing involves many risks, because the parts become more brittle before go to the oven, since the raw clay, when glazed, assimilates a large amount of water.
RAKU: the Raku is originated in Japan in the sixteenth century and has always been attached to tea ceremonial. It’s name means 'happiness and pleasure'. When Japan lost the war, it was forced to open its doors to the Western World. The first potters to enter in the country fell in love with this type of firing, which was unknown to them. One reason for this instant passion may be the proximity that the potter works with the fire.
One of the great 'advantages' of Raku is that the firing process is much faster, taking about 2 hours and allowing to see the results quickly. The pieces are removed from the still incandescent oven (with the glaze in melting point) and placed in a container with a lid containing sawdust, leaves, or other materials that give various stains by oxidation and reduction.
Thus, the final result is obtained out of the oven and in the sawdust or other combustible material. The Raku has undergone several transformations since leaving Japan. Before used only at tea ceremony pieces, currently leads to decorative pieces.
Several countries have contributed to changes in the burning process, leading to some new techniques, as the Naked Raku, the Horse Hair (burned with horse hair, sheep wool, feathers, etc.) and Mettallics Rakus (with oxides in large quantities). Tauá Cerâmica has been working in a Brazilian way to this technique, adding a bit of culture and local elements.
Ash glazes: the making of glazes is an alchemy that enchants many potters. In my opinion, the best concept for alchemy is 'the search for gold.' And that's what really potters seek when they start to mix elements and ashes with the aim of a whole new glaze, which features colors, textures, transparencies and incredible translucidezes. I love my garden and I take the leaves of various trees and grass to I use in my glazes. For me it's a way to share the joy and liveliness of my garden with my clients.
Anagama: the first oven that has been reported is the Anagama, which has only one chamber and the pieces are placed without glazes. The ashes coming from the wood becomes the glaze. The brush is the path of the fire through the parts of the piece. To this, it’s necessary a long period of firing, from 4 to 15 days. To put the pieces at the oven is a very slow process too, as we need to think of the passage of fire between the parts and ash deposits on them. In Japan, this is the most appreciated technique and is closely related to the concept of oriental beauty Wabi-sabi, the beauty of imperfection. In 2001, I built my first Anagama, the 'V Continent' in Artur Nogueira, Brazil. It was one of the first oven of the kind in Brazil. According to the guidance of Peter Callas, the oven was built and burned 14 times. He is currently being rebuilt and will slightly change its shape and size.
By Chris Rocha