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Kiln Pointers
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Estimating Temperature by the Color of the Kiln |
CONTENTS Estimating Temperature by the Color of the Kiln Recent Q&As: Repairing lid damage at the outer corner of the lid Memorable Quote ----------- ESTIMATING TEMPERATURE BY THE COLOR OF THE KILN Potters of the ancient world judged the firing temperature of their kilns by the color of the interior. Dark red meant the kiln was just beginning to get hot. They knew the firing was finished when the kiln reached a specific color, such as light orange or yellow. Judging the temperature of your kiln by color is still useful even if you have a digital controller or pyrometer. The better you understand your kiln, the more comfortable you will be around it. Once you learn the temperature colors, a quick glance at the glow around the lid or through the peephole or window will assure you that the temperature shown on the controller or pyrometer is accurate. On the other hand, a bright yellow interior when the controller shows a temperature of 1380F (748C) indicates that something is wrong and the kiln should be turned off. Checking the firing chamber color is a little easier if you turn off the overhead light. As the kiln fires, make a mental note of the firing chamber color in each temperature range. You may find that the colors listed on firing charts do not correspond to actual kilns. The color for 885 - 1200F (473 - 648C) is listed on color charts as lowest visible red to dark red. But at that temperature, a glowing kiln may, for instance, look orange to you instead of red. This is why judging the temperature of a kiln by color requires experience rather than only referring to a color chart. When you check on the kiln during a firing, look at the color of the firing chamber and guess the temperature. Then check yourself for accuracy by looking at the controller or a pyrometer. With a little practice 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. Kiln Temperature Color Scale (reprinted from the Paragon A and B Series Instruction and Service Manual) Lowest visible red to dark red: 885 - 1200F (473 - 648C) Dark red to cherry red: 1200 - 1380F (648 - 748C) Cherry red to bright cherry red: 1380 - 1500F (748 - 815C) Bright cherry red to orange: 1500 - 1650F (815 - 898C) Orange to yellow: 1650 - 2000F (898 - 1093C) Yellow to light yellow: 2000 - 2400F (1093 - 1315C) ----------- RECENT Q&As Q. The top of my kiln lid is crumbling in one of the corners near the hinge. I don't know what material to use for repair. Can you help? [A photo of the lid showed a small amount of firebrick damage limited to half an inch of depth in the outer lid surface.] A. Since the damage is limited to an outside corner of the lid, the damage is cosmetic. It should not affect the performance of the kiln, because dust will not drop into the kiln. However, you could coat the damaged area with kiln coating. That will help to prevent further erosion of the firebrick. ----------- MEMORABLE QUOTE “The best time to plant a tree is 20 years ago, the second best time is now.” --African Proverb ----------- Last Saturday night, my sister-in-law phoned and said, “A tornado is heading toward you.” A moment later, cell phones buzzed with a warning. The air was still when I stepped outside to look at the darkened sky. Only the wail of a distant siren disturbed the silence. A wall of clouds, glowing intermittently with lightning, had already passed us and moved north toward Rowlett, where it became an EF4 tornado. On Monday morning the office mood was somber. Houses in Patti’s neighborhood had disappeared. Patti’s house was okay but the power was off, so she brought her little dog, which Ashley held inside her jacket. Karen said she came out of a restaurant that night and saw the tornado from across Lake Ray Hubbard. On Sunday Adelaide helped tornado victims at the relief “command center.” During emergencies, people always come together. We hope you were safe during the storms. All of us at Paragon thank you for your friendship and wish you a Happy New Year. With best wishes, Arnold Howard Paragon Industries, L.P. – Better Designed Kilns 2011 South Town East Blvd., Mesquite, Texas 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 / ahoward@paragonweb.com / www.paragonweb.com / www.facebook.com/paragonkilns PRIVACY NOTICE: Under no circumstance do we share or sell your email address. Copyright 2015, by Paragon Industries, L.P. |
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