This piece was slipcast using Ashraf Hanna stonware clay and after bisque firing was coated in the copper matte solution and fired in a raku kiln. The top was wheel thrown and also given the same treatment but in a seperate firing so that the end result was slightly different to the main body.
 
What is Copper Matte Raku?
 
Copper Matte raku is a type of raku firing that focuses on achieving metallic, matte finishes on pottery using copper compounds in the glaze. The distinctive feature of copper matte raku is the range of vibrant colors and metallic sheens that result from the interaction of copper with the raku firing environment.
 
The Process of Copper Matte Raku
 
Creating the Glaze
 
The glaze used in copper matte raku contains copper carbonate or copper oxide as the primary colouring agent. Other ingredients in the glaze might include feldspar, silica, and various fluxes to achieve the desired melting properties and surface effects. Potters often experiment with different glaze formulations to achieve specific colors and textures.
 
Applying the Glaze
 
The glaze is applied to the bisque-fired pottery, typically through dipping, brushing, or spraying. The application needs to be even to ensure a consistent surface finish.
 
Firing
 
The glazed pottery is placed in a raku kiln, which is typically a gas-fired kiln designed for rapid heating. The kiln is heated quickly to a temperature range of approximately 1,650 to 1,850 degrees Fahrenheit (900 to 1,010 degrees Celsius).
 
The firing process usually takes about 30 to 45 minutes, during which the glaze melts and the copper compounds begin to interact with the other elements in the glaze.
 
Reduction Phase
 
After reaching the desired temperature, the red-hot pottery is removed from the kiln using long tongs and placed into a reduction chamber - a container filled with combustible materials such as sawdust, newspaper, or leaves.
 
The intense heat of the pottery ignites the combustibles, creating a reducing atmosphere (low in oxygen). The reduction atmosphere affects the copper compounds in the glaze, causing a variety of colour changes and the development of metallic sheens.
 
The pottery is then exposed to the air from time to time in order to develop certain colours in certain areas of the piece.
 
The reduction process can produce a wide range of colours, including reds, blues, greens, and purples, often with an iridescent or metallic sheen. The exact colours achieved depend on factors such as the glaze composition, firing temperature, and reduction conditions.
 
Cooling and Cleaning
 
After the desired effect has been achieved, the pottery is often quenched in water - the process locks in the colours and surface effects created during the reduction phase. Once cooled, the pottery is cleaned to remove any residual ash or soot, revealing the final copper matte finish.
 
The results of copper matte raku are somewhat unpredictable, and achieving consistent results can be challenging. Each piece is unique due to the variables involved in the firing and reduction processes.