PACKING (b) Clay to bisque fire
Packing clay: before starting make sure the kiln is clean, none of the furniture is broken or has glaze from a previous fired.
Always check to what temperature the clay you are using can and should be fired to. Over-firing clay can turn it into a liquid and destroy your kiln. Clay shrinks during firing. If you fire clay to its correct temperature, shrinking will stop, but if you under-fire it, shrinking will continue when it is re-fired. There are two ways of firing and each one has different methods.
a) The clay is fired to become bisque.
b) The clay and the decorating are fired together.
When packing clay, it does not matter if the pieces touch as they never stick to each other. Plates and lids can be piled up, bowls boxed, one upside down on top of the other and a lid can be on the article it was made for. When packing objects that are thick and heavy like tiles, leave a space between pieces to ensure that the strong gases escape during the first hours of firing, this helps the temperature to spread evenly throughout all parts of the kiln and around the ware. The effects of uneven heating and cooling are the main causes of cracking, warping and breaking and this is particularly important if the clay is thick.
Tiles are thought of as easy to make as their shape is so simple but firing them is difficult. One of the main problems is that they are large, fat and thick and if the heat differs in places it can cause warping and breaking. If the tiles are thick they can be fired standing, balanced on their sides and if not lay them onto a flat shelf covered with a thin layer of sand, which helps their movements as they contract during firing.
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