The digital controller and Kiln Sitter used on kilns are very reliable. But if they fail, they can overfire the kiln and destroy all the ware, the shelves and posts, and even the firebricks. This is why all kiln manufacturers recommend that you monitor the kiln.
Monitoring takes very little time. Just check the kiln every now and then, especially toward the expected shut-off time. Monitoring the kiln also helps you to become familiar with its operation. If you “set it and forget it,” returning to the kiln only after the firing is completed, you are missing an opportunity to learn more about firing.
Use a digital wristwatch or a small count down timer to remind yourself to check on the kiln. Decide how often you will check it. Set the digital watch’s countdown timer for that length of time. Or you can set the watch’s alarms.
Checking the Kiln from a Distance
Some people place a baby monitor near the kiln so that they can hear the relays clicking from another part of the building. If your digital controller has a temperature alarm, set it for the times that you will check the kiln. You will hear the alarm on the baby monitor.
Schedule the Firing
Write down the total firing time of all your firings in a logbook. Once you know how long a firing should take, you can arrange your schedule to be near the kiln before it shuts off. Knowing the firing time will also alert you that something may be wrong if a firing takes longer than usual.
If you would ordinarily be away when the kiln shuts off, start the firing at a different time to better suit your schedule. The Delay feature of digital kilns can turn on the kiln automatically after an elapsed period of time. Or change the firing speed so that the kiln will shut off when you are nearby.
After you turn on the kiln, use Program Review to make sure you entered the program correctly. Have your firing logbook in front of you to check each Program Review entry. Common reasons for overfiring are programming the wrong cone or inadvertently using an extended hold time.
The Kiln Sitter
Be sure to load the correct cone in the Kiln Sitter. Double-check the cone number on the box. Set the Limit Timer for no more than 30 – 60 minutes beyond the expected firing time.
Make sure the Kiln Sitter is free of obstructions inside and out. Ware toppling over against the Kiln Sitter cone can cause an overfire. A power cord draped too close to the Kiln Sitter can prevent the weight from dropping all the way and shutting off the kiln.
Check the Color Around the Lid
Note the color of the kiln interior, which shows at the peepholes and around the lid or door. After awhile you can estimate, with surprising accuracy, when the kiln is about to shut off just by observing the color inside the kiln. If the kiln seems to be firing too long or if the interior color turns too bright, look through a peephole at the pyrometric cones on the shelf.
Witness Cones in Ceramic Firings
The pyrometric witness cone is a record of the firing. Use witness cones in every ceramic firing, even in electronic kilns. For one thing, the witness cones will verify the accuracy of your electronic controller and alert you to any thermocouple temperature drift.
If a firing takes longer than usual and you suspect the kiln is overfiring, check the cones through the peephole. Wear firing safety glasses when looking into the peephole. Firing glasses not only protect your eyes but also make the cones easier to see.
No matter how automated the kiln, firing still needs human attention. It takes just a moment to check the kiln near shut-off.