There are a multitude of artists and companies that specialize in English fine bone china. It is prized for its ability to let light shine through it even though it is opaque. The ability to achieve this effect is based on kiln firing ceramics at high temperatures. This must be done with precision or the china will crack and break. Kiln operators must know the exact mix of the substances in the clay pieces to select the correct firing temperature. Heating and cooling of the kiln are a major factor during firing.
The kiln must heat and cool at the correct speed to avoid damage to the pieces inside. Experienced kiln operators know the thermal abilities of their kilns and take that into account when operating them. Each operator knows how long they can hold at the proper temperature. Slow heating and cooling are part of their operation to ensure as many pieces as possible make it through the firing process. Broken pieces because of improper firing can damage other pieces in the kiln.
Ceramics that explode during firing can damage the kiln shelves. This must be avoided at all costs. While shelves can be replaced, it is an added expense to the operator and ceramics artist. If the shelf damage is not noted immediately, then other ceramic pieces can be damaged when that kiln shelf is next used. Those who craft fine china require every piece they entrust to the operator get the best treatment. Kiln operators who have been long in their craft have a reputation for many successful firings.
The temperatures a kiln must reach for fine bone china are very high. China ceramics begin to convert from clay to ceramic at approximately 1650 degrees Fahrenheit. The operator must continue to raise the temperature until it reaches at least 1900 degrees Fahrenheit. Firing temperatures for bone china go as high as 2500 degrees. The operator knows how much heat and the length of time it is applied to fire the ceramics properly. Each time a group of ceramics is fired, the kiln must be taken slowly to the necessary temperature. The kiln must also be allowed to cool slowly. Knowledge and experience are the tools kiln operators use to make this exquisite substance at the precise temperatures required.