Ceramic Witness Cones

Cones indicate whether the ware received an adequate amount of heatwork to properly mature the clay or glaze.

Ceramic witness cones.

Since cones act like clay and glaze some ceramic artists fire cones only often for wood salt and raku no pyrometers kiln sitters etc. 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. 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. In 1896 the first orton pyrometric witness cone was produced by dr.

Because cones are made from carefully formulated ceramic compositions they bend reliably at specific temperature ranges. 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. Cone 022 is the cone that will deform at the lowest temperature 1087f and cone 32 is the cone that deforms at the highest temperature 3106f 1708c. These are the large standard or self supporting cones that you put on the kiln shelves when firing a kiln.

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. I have done a few glaze firing test in my kiln test one reaching 1240 test 2 reaching 1222 and test 3 reaching 1220. But each time the cone 6 witness cones have over fired. After firing a kiln a simple glance at the cone can tell if the firing was sucessful.

They will indicate the temperature heat work that location on that shelf reached thus they witness the true temperature achieved. Self supportiong cones are recomended by glaze and kiln manufacturers to achieve the best results. A cone pack sometimes called a witness cone see definition below is made by placing a guide cone a firing cone and a guard cone in a coil of clay. A properly fired cone will bend over with the tip of the cone almost touching the shelf.