TECHNIQUES AND PROCESSES - GENERAL:
Kiln and Firing
Stacking the Kiln
When pieces are bone-dry at room temperature, we are ready to load them into the kiln for their first firing, what in ceramics we call bisque firing.
The method of stacking a kiln depends on the firing we are going to carry out. It is different to prepare a batch of raw pieces than one of glazed pieces. In the case of the raw pieces, that is, those that have not been yet fired, they should be completely dry and can be placed directly on the kiln shelves. In order to optimize the inner space, they can even pile up or touch each other.
Firing and Temperature
After loading the kiln we begin with a slow firing, with the air vents always open to favor the exit of water vapor. Temperature will increase gradually. We control this process with a digital programmer in which we set a cycle that prevents sudden temperature variations. Up to 400 C°, the increase should be very slow, more or less 100 C° by every hour and a half. From there, the progression can accelerate since the most critical moment of firing, in which the big cracks generally occur, will have passed.
We turn off the kiln at 1060 C°, which technicians consider a medium fire temperature. Then a very sudden descent of temperature occurs, stabilizing at approximately 500 C°, after which it continues to cool slowly. After 20 to 24 hours, when the kiln is almost at room temperature, we can open it to see the result of the work.