There are two basic types of kiln: intermittent and continuous. With an intermittent kiln, the wares are placed inside, then the kiln is heated up and allowed to cool after the appropriate period. Continuous kilns are more common in industrial applications and are built in the form of a tunnel where only the central section is heated and the wares move through on a trolley. An alternative arrangement is to have the heating on a moveable track to pass over the wares. Either of these is more energy efficient than repeatedly heating and cooling the same area but is not practical for the hobby enthusiast or a small scale operation.
Function of a kiln lining
Kiln linings are the materials used inside ceramic kilns. The purpose of a kiln lining is to prevent the kiln walls from overheating and energy being wasted. This can be achieved using dense firebricks and Refractory Mortar, insulation bricks and refractory mortar, refractory castable or ceramic fibre (usually in the form of modules). Low thermal mass materials have the advantage of higher turnaround as the kiln will heat up and cool down quickly, whereas higher thermal mass materials are more rugged and wear resistant.
Read our article to find out more about kilns and kiln linings.
Properties of kiln linings
Aside from the materials being low thermal mass, the materials should also be lightweight such as with insulation bricks (Grade 26) and ceramic fibre products, so as to reduce the cooling time of the kiln after firing. The insulation bricks should be used in conjunction with Vitset 45 refractory mortar. Tunnel kilns with consistent temperature do not require the mortar as they are usually lined with dense firebricks like our clay firebricks with 42% alumina content.
The materials should also be low in iron since the work is commonly white in colour and excessive iron pickup will generate black or green spots in combination with the ceramic being fired. Therefore, it is also crucial to coat ceramic fibre with Zircon paint refractory coating to avoid stray fibres dropping onto the work, especially if it is glazed work.