Orton Pyrometric Cones deform progressively under advancing heat at fairly regular temperature levels. They serve as accurate indicators of heatwork in the firing chamber. Designed for use with a kiln sitter. Cone Temperature Chart. Temperature equivalents for Orton large cones when fired at approximately 238 degrees C (460 degrees F) per hour. Cones supplied in box of 50 single number. Cannot be assorted. Cone 04 (1908 degrees C / 3466 degrees F).