|Monthly Tech-Tip |
This is not supposed to happen. The guide cone should be flattened. And the guard cone should not be starting. But what you see does happen often. this indicates that the real-world performance of cones does not always match the theoretical behaviour. This is because the bending range of many cones overlap that of their neighbours. And performance is affected when firings are slower and faster than the 60F/hr reference given by Orton.
Orton says “90 angular degrees is considered the endpoint of cone bending”. First, let's assume the normal: Examination of cones on kiln-opening to verify controller operation. Consider the cone on the left: The tip is touching. But it is also beginning to buckle, that means it was touching for a while before the firing ended . Who knows how long! The second one is not touching, but has still fallen a little too far. Why do we say that? The third one, positioned on the Orton guide, has reached the recommended 90 degrees. This demonstrates a good reason why self supporting cones are much better than standard ones: They are not touching when considered done. And standard cones, when sent in a 3/4" plaque, have a less consistent bending behaviour.
Devices that melt and bend in a ceramic kiln at specific temperatures when subjected to specific up ramps. Today, cones are used to calibrate controllers.