Pottery, Sculpture & Raku
What is Raku?
Raku is a firing technique. After a piece of pottery is made, it is allowed to dry. This drying process takes from one to three weeks depending on the size of the work. When the work is completely dry it is called green ware. The green ware is coated in selected areas with a special slip called terra sigillata. Three coats of terra sigillata are applied to the green ware. The pots are then polished to a high sheen between each coat using a rounded stone or a soft cloth. The pottery is then fired in the kiln to a temperature of 1700 degrees Fahrenheit. This makes the clay hard enough to handle without breaking.
The clay is glazed with a low fire glaze and then fired in a red-hot kiln, to 1800 degrees Fahrenheit. As soon as the glaze has melted, a process that you watch, the pottery is removed from the hot kiln with long tongs. When the red-hot pottery comes into contact with the air, cooling takes place and instantly the glaze crackles. Still red-hot, the pottery is placed into a container that has been filled with a combustible material such as straw, newspaper, sawdust, leaves, etc. As soon as the hot pottery touches the combustible material a fire starts in the container. A lid is placed on top of the container snuffing out the fire and creating carbon (smoke) thus reducing the oxygen in the container. This process is called reduction.
Raku is a firing technique. After a piece of pottery is made, it is allowed to dry. This drying process takes from one to three weeks depending on the size of the work. When the work is completely dry it is called green ware. The green ware is coated in selected areas with a special slip called terra sigillata. Three coats of terra sigillata are applied to the green ware. The pots are then polished to a high sheen between each coat using a rounded stone or a soft cloth. The pottery is then fired in the kiln to a temperature of 1700 degrees Fahrenheit. This makes the clay hard enough to handle without breaking.
The clay is glazed with a low fire glaze and then fired in a red-hot kiln, to 1800 degrees Fahrenheit. As soon as the glaze has melted, a process that you watch, the pottery is removed from the hot kiln with long tongs. When the red-hot pottery comes into contact with the air, cooling takes place and instantly the glaze crackles. Still red-hot, the pottery is placed into a container that has been filled with a combustible material such as straw, newspaper, sawdust, leaves, etc. As soon as the hot pottery touches the combustible material a fire starts in the container. A lid is placed on top of the container snuffing out the fire and creating carbon (smoke) thus reducing the oxygen in the container. This process is called reduction.
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The pottery is left in the oxygen free atmosphere for about twenty minutes. The smoky atmosphere helps develop the beautiful lustre that we see on finished clay pieces. Carbon enters into the crackle where a clear glaze has been applied, this is called carbon trap. Smoke also attacks the raw clay where terra sigillata has been applied and leaves the clay with a beautiful black shiny surface. After twenty minutes in the reduction container, the piece is placed in water for quenching. This cools the pottery and stops all chemical reactions. If the piece survives all these processes, the result will be a delicate vessel with a beautiful lustrous or crackled glaze, and shiny black surface that can only be obtained through the process of what we call Raku. |
Gallery
All images copyright Bonnie Lee Anderson.