One attribute that may determine a clay’s resulting characteristics is the ‘table’ in which the piece was actually placed in the kiln during firing. During firing, each table will naturally be exposed to varying temperatures due to its particular placement in the kiln. For example, ‘Table 1’ on average will experience temperatures of ~1150ºC, ‘Table 2’ ~1170ºC, ‘Table 3’ ~1190ºC, ‘Table 4’ ~1210ºC, and so forth. In fact, as the table number increases, the temperature rises by ~20ºC (e.g., ‘Table 1.5’ will be at ~1160ºC, ‘Table 2.5’ ~1180ºC, etc.).
Additionally, each table is divided into sub-sections: ‘up close’, ‘down close’, ‘up flat’, ‘down flat’, etc. These sub-sections will also yield distinct results despite pieces having the exact same clay, shape, table, and position. However, it is important to note that in addition to these variables, results will once again vary after EVERY batch is fired in the kiln, further adding variability to the results! In fact, such volatility in the output is the very reason why kilns utilize firing disks prior to firing the actual pieces, as it will ultimately provide practicable insights of the outcome.
In the case of publicly-owned electric kilns, temperature is determined by electronic thermometers which are too frequently used by the community, thus yielding unreliable and inaccurate readings. Due to the inaccuracy of the thermometer, firing will naturally result into slightly wrong temperatures.
Another factor to consider is that certain clays react differently depending on the firing temperature; for example, some clays (i.e., Zhuni) will have a greater shrinkage rate at higher temperatures, thus increasing the probability of complications and failure. To decrease the possibility of a costly outcome, kiln factories will often err on the side of caution and choose to drop the table number and lower the temperature of the kiln to ensure maximum yield. By wholly manipulating the table number and kiln temperature, the results are never consistent! This unreliability has since beckoned well-to-do artists to build and use their privately-owned electric kilns - a luxury that the majority of zisha craftsmen simply could not afford.
Clay also plays a significant role in the outcome of a particular piece. For example, two pieces made out of Di Cao Qing clay from the No. 4 mine will yield different results as the Di Cao Qing clay on one piece will likely have come from a different section of an ore, and/or from a different batch, and/or have been exposed to different production methods. As a result, features of the clay will typically vary from one another.
The age of the clay also plays a vital role in the overall look of the finished product. In fact, the older the clay, the less time and lower firing temperature it will need in the kiln. (See "Is 'Old' Clay Always a Better Clay ) This, of course, further explains the advantages of using finely aged clay, since low firing temperatures result to a more stable and predictable outcome. Thus, it behooves a kiln to be fired at lower temperatures, as it will allow for a successful batch and an increased likelihood of reproducing a desired aesthetic (e.g., color, texture, durability, etc). In reality, however, this is often not the case…
It is for these very reasons why determining a piece’s exact firing temperature is a pointless and unrealistic pursuit. At no point does a firing temperature reliably influences a piece’s overall features, worth, and integrity. Therefore, here at Yann Zisha Gallery, we greatly encourage our buyers to look beyond this insignificant variable, as it will often lead one to miss the very piece one may have indeed been longing for!