It is for this reason Orton developed Self-supporting witness cones some 20 years ago, where mounting height and angle is fixed. It typically takes 15 to 25 minutes for a cone to bend, depending upon the cone number. The cone bends slowly at first but once it reaches the halfway point, it bends quickly. Firing ceramics is much like baking, except temperatures are higher. Ceramics can be fired over a range of temperatures.
Some products have a wide firing range while others have a narrow range.
Firing to a slightly lower temperature requires the ware to be held for a longer time, just as it would be done if one were baking a turkey. We refer to this absorption of heat as 'heatwork'. When the amount of heatwork for two firings is the same, the pieces will look identical, even if one is fired to a higher temperature for a short time and another is fired at a lower temperature for a longer time. Since cones measure heatwork, all manufacturers recommend the cone number to which their product should be fired. Guide Cone - one cone number cooler than firing cone.