Firing area should be well ventilated.  The kiln door should be left partially open about an inch or two depending on the loading for oxidizing atmosphere until all fumes and smoke disappear. The rate of temperature elevation must be gradual to permit the organic substances to burn off cleanly.  Otherwise, blistering or charring of the coating may occur resulting to undesirable film. The door is then closed to complete the firing cycle. The ideal maximum firing temperature corresponds to the softening temperature of the substrate.  Overfiring may produce wash out color or indented coating areas.  However, firing at low temperature saves energy so trials may be done to determine the acceptable firing cycle.  Space the wares so as to have a uniform temperature distribution in the kiln.  Lehr firing usually has adequate oxidation atmosphere. However, heavy loading may require slight force ventilation to exhaust fumes and smoke.

 Approximate firing temperature (use only as guide):

                                                           °C                       °F                      Cone

Lead glass                                      500                       930

Lime glass                                       600                     1110                     022

Borosilicate glass                           650                     1200                     020

Soft glaze earthenware                  720                      1325                    018

Glaze pottery                                    745                     1375                    017

Hard glaze china or porcelain        790                     1450                     016