I chose Raku as a clay management technique, rapid firing is an effective choice for creating artifacts after applying colours, such as glazes or crystallines. Both of these materials contain a glassy component and can be mixed or overlaid with metal oxides like copper, iron, or cobalt, thereby generating a wide range of colours and metallic effects known as lustres.
The aspect that most fascinates me in the Raku technique with oxygen reduction is the need to extract the artifacts from the kiln while they are still incandescent, at a temperature just above 900 degrees Celsius. Afterwards, they are cooled using various methods, such as exposure to air, direct immersion in water, or placement inside bins containing combustible materials like straw, paper, leaves, sawdust, or fabric rags. This cooling phase inevitably causes the combustion of the combustible materials in contact with the glowing clay artifacts, generating smoke. This smoke leads to a further reduction of oxygen inside the bin where I have placed my work. This reduction helps to create and enhance the chromatic effects of the metal oxides used to colour the artifact.
The cooling method adopted, although a harsh process for the incandescent artifact, contributes to the desired final result (although it is not always achieved). The timing and method of oxygen reduction can only be partially managed through the choice of time dedicated to this process. However, it is important to note that the same aesthetic results are often not achieved from one reduction cycle to another.
Thus, several interconnected factors contribute to the final outcome of the Raku piece. These include the type of combustible material used to generate smoke and reduce oxygen, the temperature and humidity of the surrounding environment, and the speed of the cooling process. These combined parameters determine the final aesthetic result of the Raku work.
You may wonder why the artifacts do not shatter into a thousand pieces when subjected to the thermal shock described earlier. Indeed, this can sometimes happen, and I personally do not get discouraged because in these cases, there is an opportunity to work on reassembling the object using the ancient technique of Kintsugi. However, in most cases, the artifacts remain intact thanks to the use of semi-refractory or refractory clay. The clay mixture contains a component called chamotte, which is nothing but already fired and finely ground clay. This mixture gives the artifact greater resistance to the thermal shocks to which it is subjected.
Another aspect of the Raku technique is that if the final result of the piece does not satisfy us, it is possible to repeat the entire process, starting again from the application of colours. In this way, there is always the possibility of achieving a different and surprising result.