|Monthly Tech-Tip |
Orton says: “If the Guard Cone has bent, you have exceeded the best time-temperature relationship”. We have found that bending the firing cone down to 90 degrees most often starts the guard cone. So, if the quard cone is starting, we have gotten into the habit of judging the firing as accurate when the firing cone reaches the 3 o’clock position. If the guide cone is not started we judge a firing as accurate when the firing cone is at 5 o'clock, before touching.
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.