Earthenware or stoneware structure which encloses one or many pots in the kiln during firing, sometimes just a large lidded pot which houses a smaller pot. The purpose of the saggar is to protect the fired items from direct flames and gases from the wood or coal, to prevent ash and sand from blemishing the ceramics and to ensure an even temperature. Chinese saggars would normally contain more than one piece and were also put one on top of the other to enhance the number of pieces that could be fired at the same time. A pile of saggars could be some ten feet high and the use of saggars was therefore an important part of the Chinese kiln technology. Several different types of saggars were used in different areas during different times, a feature, which are of importance for the attribution of antique pottery.
Saggars have been made in different shapes and for different firing methods throughout the ceramic history of China. Some for up side down firing on the unglazed rims (fushao) of the bowls or dishes, some where the porcelain standing upright and resting on different kinds of firing supports such as rings, tubes, pads or pontils.
For example, Northern Song Dynasty Qingbai porcelain was sometimes fired individually in saggars (the fireproof clay case) that were stacked on top of each other in the kiln. If the temperature became too hot the porcelain items could warp and sag, the glaze may run or even a stack of saggars could shift and possibly collapse, resulting in the porcelain items becoming fused to the saggar in which they were being fired.