Firing is the most delicate and final stage of all shaping and glazing steps. Ceramic bodies contain micropores. During firing, the pores in the ceramic body move away from the body and the product gains strength. In this phase, irreversible chemical and physical changes occur in the ceramic body. While your product is still moist, you have the opportunity to retouch the product in case of some flaws made during the shaping and drying stages of the ceramic but, the sintering stage is an irreversible process. The sintered product is a final product. Certain temperature levels and waiting times during the firing, the highest temperature and the waiting time at this point are important factors for a good firing result.
BISQUE FIRING SCHEDULE CONE 04
Below is one of the most effective bisque firing program to us for clays like earthenware, porcelain, stoneware.
Bisque firing is the first firing done for your ceramic product to gain strength by getting away from the shaping water when you place it in the kiln for the first firing after the drying phase of your ceramic object is completed.
The best bisque firing schedule of Crafist is as follows.
STEP 1: 100°C in 4 Hours
STEP 2: 427°C in 6 hours
STEP 3: 3 hours 30 minutes 705°C
STEP 4: 2 hours 15 minutes 1040°C up and off
• Step 1, if you are not sure whether your products are completely dry,
o If the water content in your products is high and you will do the glazing process and put it in the kiln immediately if your products are thick and large objects...
o Since water boils at 100°C, you should not switch to Step 2 until you are sure that all physical water has come out and evaporation has stopped. With the help of a mirror, you can check whether evaporation continues from your kiln's vent hole.
o If your products have been drying for a long time or if you have previously dried them at 100°C, you can speed up this step.
o If evaporation is not visible, you can switch to step 2 by closing the kiln's vent hole.
• In step 2, organic materials and gases in the clays are removed from the body in this segment.
o This step is the longest stage of firing. Because all clays contain organic materials and if they are not given enough time to be thrown out, your glazed object will continue to produce gas during firing. This causes pinholes on the glazed surface.
• In step 3, chemically bound water is removed in this step
o At the same time, transformations of quartz becomes here
o It is the most important stage of heating and cooling.
o This process is stressful for clay due to the volumetric transformations of quartz. If it is passed quickly, cracks may occur in your forms.
• Bisque firing of your ceramic body is now completed at 1040°C in Seg4.
o If cooking took 15 hours, then cooling should take at least 15 hours. It is best to leave the kiln to cool naturally to prevent the long-term use of the kiln elements (refractory and resistance wires) and the cooling of the products inside with natural air.
o The door should not be opened before the kiln's temperature drops below 200 °C.
o You can get your products when your kiln's temperature reaches 60 °C - 70 °C.
GLAZED FIRING SAMPLE PROGRAMS
LOW FIRE
SEG 1: 100°C in 4 Hours
SEG 2: 427°C in 6 hours
SEG 3: 3 hours 30 minutes 705°C
SEG 4: 2 hours 15 minutes 1040°C up and off
MID-RANGE
STONEWARE, PORCELAIN
SEG 1: 100°C in 4 Hours
SEG 2: 427°C in 6 hours
SEG 3: 3 hours 30 minutes 705°C
SEG 4: 3 hours at 1145°C
SEG 5: WAIT 15MIN at 1145°C AND OFF
SEG 1: 100°C in 4 Hours
SEG 2: 427°C in 6 hours
SEG 3: 3 hours 30 minutes 705°C
SEG 4: 3 Hours 1230°C
SEG 5: 1230°C WAIT 15MIN AND OFF