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Kiln Pointers
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False Element Readings with the Ohmmeter |
CONTENTS False Element Readings with the Ohmmeter Reader Response: Resistance readings; light around the lid of a kiln Recent Q&As: Wax resist used by potters A Story: The Glass Fusing Presentation Memorable Quote News: Paragon Introduces Darby Dipper Crucible Kiln ----------- FALSE ELEMENT READINGS WITH THE OHMMETER The ohmmeter is used to check a kiln’s heating elements. It measures electrical resistance in ohms. (Note: Always disconnect power to the kiln before using an ohmmeter.) The ohmmeter, though a useful instrument, can give false readings in the following ways: 1) The ohmmeter has two wires with probes. Touch the probes to the element connectors or element ends. Corrosion on the connectors where the probes touch can cause inaccurate readings. Sand a spot on the brass element connectors with emery cloth to remove the corrosion. 2) There are two element connectors for each element that you test. In rare cases you will have to temporarily disconnect a lead wire that goes from one of the element connectors to the switch or relay. Multiple elements wired in parallel to a single switch or relay can cause false readings. This is because the electricity from the ohmmeter battery can go past a broken element and through another element wired in parallel. Check the kiln’s wiring diagram to determine whether you should disconnect wires from an element connector. 3) A broken element can occasionally show continuity on an ohmmeter, because as the element cools, the broken ends touch. With the ends touching, electricity can still travel through the element. Yet when you fire the kiln, the element will produce little, if any, heat. (In this case, the resistance will be much higher than the rated resistance shown in the kiln's wiring diagram.) ----------- READER RESPONSE In the last Kiln Pointer someone asked, “Should I check the elements with an ohmmeter and change them if the readings are low . . . ?” Hugo Gavarini of far-away Patagonia, Argentina asked, “On element wear increase, would resistivity increase or decrease? And if possible, why?” The original questioner asked if elements should be changed when the readings are low. Actually, elements should be changed when the ohmmeter readings are high. This seems counter-intuitive--one would think that the readings would become low as the elements age. The ohmmeter measures resistance, or ohms. The higher the number of ohms, the slower the elements will fire. As heating elements age, the element wire becomes thinner. This increases the resistance, or number of ohms. The last Kiln Pointer explained that the thin line of light under the kiln lid or door is normal. John Rodgers of Chelsea, Alabama wrote, “This one answered the question about the light coming from under the lid. I was firing tonight and sat in the dark, contemplating that bright line. You answered my question.” ----------- RECENT Q&As Q. Does wax resist used in pottery firings void the Paragon kiln warranty? A. No. Wax resist does not void the warranty. As long as you do not use an excessive amount, wax resist in pottery firings won’t hurt the elements or the firebricks. Please make sure the kiln is well ventilated. ----------- A STORY: THE GLASS FUSING PRESENTATION By Bill Hosford (Lisbon, Iowa) whosford@mchsi.com I had the great pleasure of being invited to demonstrate glass fusing at the Perry, Iowa “Arts on the Prairie” festival this past weekend. The festival took place in at least six buildings clustered in the downtown area. These included the outstanding Hotel Pattee, historic Carnegie Library and the newer Perry Public Library. Artists showed their creations, writers and poets read from their books, and musicians entertained the public. My program was part of the Public Library’s Youth Activities contribution to the festival. I started by reading a short poem and then jumped right into the fused glass demo. The audience was small enough that I could abandon my expansive PowerPoint slide show and talk through the process “up close and personal.” We investigated the basic tools, different types of glass, basic straight and circle breaks, and assembly of small pendants. I didn’t bring my Paragon GF-6B kiln, but I did bring the shelf and used my PowerPoint slides, which showed the kiln and described the firing steps. There were many questions and requests for more detailed explanations. I found I couldn’t cover as much as I had planned in the hour I was allotted. Of course, being a retired teacher-librarian, I provided a “Glassary” and “Resource List” (think “Bibliography”) for the participants. Perry had it all together for this event, and I am looking forward to returning next year. Maybe I’ll bring my kiln and do hands-on “cutting and assembly” activities on Saturday, fire the pieces overnight, and do “finishing” on Sunday. If you have done anything like this, I would appreciate any suggestions. ----------- MEMORABLE QUOTE “Even after 55 years of making pots, opening a fully loaded kiln is still really exciting.” –Mel Jacobson, a potter in Minnetonka, Minnesota ----------- NEWS: PARAGON INTRODUCES DARBY DIPPER CRUCIBLE KILN The new Darby Dipper crucible kiln has a separate wall-mounted control panel and holds one crucible. You can see the new crucible kiln here: http://www.paragonweb.com/Darby_Dipper.cfm ----------- When the company founder, the late Frances Darby, still worked at Paragon, the office employees gathered in the printing department for our Thanksgiving lunch. We sat at long tables surrounded by shelves stacked with brochures and office forms. The print shop resounded with booming laughter--especially that of Frances Darby. This week at Thanksgiving lunch, cooking smells will waft through the office and the inspection area, and we will think about how grateful we are that you are part of our lives. All of us at Paragon wish you a happy and safe Thanksgiving, wherever you may be. Thank you, 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 2011, by Paragon Industries, L.P. |
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