Ceramic Witness Cones

In 1896 the first orton pyrometric witness cone was produced by dr.

Ceramic witness cones. These are the large standard or self supporting cones that you put on the kiln shelves when firing a kiln. Everyone should fire with witness cones. Cones enable you to determine when your kiln has reached the desired temperature if the kiln was evenly heated and whether a problem arose during the firing. They will indicate the temperature heat work that location on that shelf reached thus they witness the true temperature achieved.

I have done a few glaze firing test in my kiln test one reaching 1240 test 2 reaching 1222 and test 3 reaching 1220. What could i be doing. Because cones are made from carefully formulated ceramic compositions they bend reliably at specific temperature ranges. After firing a kiln a simple glance at the cone can tell if the firing was sucessful.

But each time the cone 6 witness cones have over fired. The guide cone is a cone cooler than the intended temperature the firing cone is the temperature you are firing to and the guard cone is one cone hotter than you are firing. Edward orton jr s standard pyrometric cone company to document the proper attainment of heat work thus greatly expanding the application of scientific principles to industrial ceramic manufacturing. As firing measurement witness cones viewed through a kiln spy peep hole are the most accurate measure of a kiln s firing progress and for deciding when to shut down the kiln.

Cones indicate whether the ware received an adequate amount of heatwork to properly mature the clay or glaze. A properly fired cone will bend over with the tip of the cone almost touching the shelf. Self supportiong cones are recomended by glaze and kiln manufacturers to achieve the best results. Since cones act like clay and glaze some ceramic artists fire cones only often for wood salt and raku no pyrometers kiln sitters etc.