Arnold Howard, a former employee at Paragon Industries, is now an independent kiln technician at Howard Kiln Services. For those who don't know him... Arnold started at Paragon in 1977 and worked there for 42 years! Repairing kilns and helping people is Arnold's passion! He is a wealth of knowledge and we welcome his insight!
Q. Why would someone choose mercury relays over solid state relays? Is there an advantage to one over the other?
Mercury relays are extremely reliable. They rarely fail even in glass schools that fire kilns every day on long annealing cycles. Solid state relays are just as reliable. But they produce heat, which must be dissipated, or they will fail. To prevent overheating, solid state relays are mounted in the control panel of the kiln as far away as possible from the firing chamber. Or they are mounted on aluminum plates that pull the heat away from the relays. The kiln industry is moving toward solid state relays because of state environmental regulations.
Q. Can I make a converter plug so my 240V-30 amp kiln can plug into a 240V-50 amp receptacle? Is that dangerous?
It isn’t dangerous. The Paragon TnF-82 is a 30 amp kiln, yet it has a 50 amp plug for a 50 amp wall receptacle. The 50 amp circuit breaker will still protect the 30 amp kiln from an electrical short. The disadvantage to a converter plug is that it adds an extra connection (the converter plug) to the circuit. If you make a converter plug, check the temperature of the cord from time to time during operation.
Q. My kiln temps keep bouncing 10F degrees up and 10F degrees down from the set temperature. I work on delicate things and proper temps are crucial, why can't the kiln be more exact?
The thermocouple type has a lot to do with temperature fluctuation during holds. The thermocouple reads the temperature inside the kiln. A heavy thermocouple with thick wires responds more slowly to temperature changes than a thermocouple with thinner wires. The slow response time of the thermocouple adds fluctuation to temperature holds. A sheathed thermocouple, which is the type that has a metal covering, adds more fluctuation than a thermocouple with a bare welded tip. To reduce temperature fluctuation, slow down the firing rate before the kiln reaches the hold temperature. Some controllers do this automatically.
Q. I think my kiln has a hot spot/cold spot! Why does this happen, and how can I fix it?
An open peephole can cause a cold spot in your kiln. For instance, if the kiln is equipped with a downdraft vent and the peephole plugs are left out, the bottom of the kiln will become cooler. A lid that rises in the front can cause a cold spot in the top of the kiln. A front-opening kiln that doesn’t have elements in the door will be cooler at the front than at the walls. The easiest way to improve heat distribution is to slow down the firing rate. You can improve heat distribution by adding more thermal mass to a hot spot and removing thermal mass from a cold spot. In a pottery kiln, add more ware to the hot area and less ware to the cool area. If the edges of a shelf in a glass kiln are getting too hot, place 2” wide strips of cordierite shelves along the hot outer edges.
Q. What's the lifespan of my thermocouple? How often should someone change it to keep the temps consistent?
The hotter the firings, the shorter the life of the thermocouple. Thermocouples in glass kilns last much longer than the ones in pottery kilns because glass is fired to lower temperatures than pottery. Recently I saw a 15-year-old glass kiln that still had the original thermocouple. Heavy, 8-gauge thermocouples last longer than 14-gauge thermocouples because 8-gauge wire is much thicker than 14-gauge. To know how long your thermocouple lasts, look at the welded tip. A flaky tip indicates a lot of wear. Keep a kiln maintenance log book and record the number of firings between parts changes.
Q. Word is.... I should change my mechanical relays every 18 months to 3 years. My friend has had her kiln 8 years and has never changed hers and everything is fine. Who's right, and does this really matter?
The lifespan of a mechanical relay is not the same for all kilns. Inside the relay are electrical contacts that make the clicking sound you are familiar with. The higher the amount of electricity that goes through the contacts, the shorter the relay life. A kiln with several relays may have less amperage (electricity) going through each relay than a kiln that has only one relay. And a small kiln that plugs into a household outlet may not ever need a new relay, because the kiln uses so little electricity. Another factor is the number of clicks, or cycles, in your firings. The higher the number of clicks, the sooner the relay wears out. Long, slow annealing times add more wear to the relays than a glass fusing that doesn’t require an annealing period. Relays wear out sooner when exposed to excessive heat. In hot weather, circulate the air around the kiln with fans. Your relays will last longer if they are kept cool. Keep a maintenance record of your kilns. Record the date that parts are replaced, and the number of firings that you obtained from those parts. This will give you an accurate estimate of the life span of your relays. Use that information to change the relays before the end of their expected life span.
Q. The brick in my lid is cracking, I've tried lid cement, but it keeps flaking off. Other than a new lid, what are my options?
Kiln cement applied to the inner surface of a lid will flake off unless the cement coating is very thin. This is because of the difference in coefficient of expansion between the cement and the firebricks. The coating should be so thin that you can still see the firebrick surface under the wet coating. To apply kiln cement, dilute it to the consistency of coffee cream. Brush it on, and immediately wipe off the coating with a rag. Dust can also fall from cracks in the lid. You can repair cracks by applying a very thin coating of ITC 100, a versatile high-temperature coating made by ITC Coatings.
Q. On a small kiln, how important is it that I have both side and top firing elements? Does it matter? It depends on the kiln. A small 8” x 8” glass kiln doesn’t need top elements. Side elements are sufficient because the firing chamber is so small and the heat distribution is even, without top elements. The larger the kiln, the greater the need for both side and top elements. Sometimes, the edges of a shelf tend to be a little cool in a medium-size glass kiln that has only top elements. Since the walls have no elements, the insulation in the walls absorbs heat from the rest of the kiln. This is because the walls are a thermal mass.
Q. I need a longer cord! Why can't I use a heavy duty extension cord?
Fire marshals prohibit running kilns with extension cords. This is because an extension cord is more likely to overheat than the kiln cord alone, and an extension cord increases the tripping hazard. When I worked for Paragon, a fire safety inspector noticed that a light table was connected to an extension cord. He made me remove the extension cord and plug the light table directly into a new wall outlet. And the light table used only 100 watts! For your own safety, avoid using extension cords on your kiln.
Q. Occasionally, when the kiln cycles, my lights flicker. Should I worry about this?
The flickering lights mean your kiln is pulling a lot of amperage. This is not a safety hazard as long as the circuits have the proper wire thickness and circuit breaker sizes, and the total electricity used in the building does not exceed the capacity of the main wires that come into the building. To reduce the flickering, try to run fewer heavy-amperage appliances when the kiln is firing.
Q. My new SC2 Pro was supposed to have a soft-close door to reduce vibrations. It does not. How can this be adjusted?
Bud Ashlock, the engineer who designed the SC-2 Pro, said the door catch is located on the bottom edge of the door, just below the handle. This catch consists of a spring loaded ball housed in a brass barrel. The outer diameter of this brass barrel is threaded, so it can be screwed in and out to adjust the tension on the door. Simply adjust this barrel to get the tension you want.
Q. My kiln consistently fires too hot! How do I fix this problem?
The thermocouple, which senses the temperature in a digital kiln, may have drifted in temperature. This happens to K-type thermocouples in pottery kilns (less often in glass kilns). Or, the kiln sitter on a non-digital kiln may need to be calibrated with a firing gauge. To correct for thermocouple inaccuracy, adjust the Thermocouple Offset setting. Please see the digital controller instruction manual that came with your kiln. If you can't find it... Kiln Frog has digital versions on their website. Thermocouple Offset should be listed on the contents page. It is a simple way to “recalibrate” the controller to compensate for the thermocouple drift. If you have never heard of Thermocouple Offset, you are not alone. A few years ago, I asked a customer service rep at Paragon how often customers used Thermocouple Offset. She said..."Over a period of several years, she had never heard of a customer using it! Most people just fire to a different temperature or add hold time to compensate for temperature drift."
Q. I have a Paragon bench-mark 16 with fiber walls, about 3-4 years old. The walls are intact but the fiber on the entire rim is corroding. It started with a few dents and now has deep gauges. Some heat must be escaping but no problems with firing programs yet. The inside lid has metal trim and is rusting. Is kiln safe to use, and is it worthwhile buying the special filler sold by Paragon?
If the gouges in the top of the walls are ¼” deep or more, you should fill them with Pyrolite, the ceramic fiber repair filler. You can lightly sand the rusted metal trim to remove loose particles. As this type of wear is unusual, I would suggest contacting Paragon for more assistance.
Q. Can a 220v European plug be changed to 220v US plug and run on it?
The standard voltage in the U.S. is 240 volts, not 220. In most residential studios, you will be running your European kiln on a 240 volt circuit in the US. If you are in a commercial space, the voltage may be 208 instead of 240. The issue will be that a 220 volt kiln on 240 or 208 volts may pull too much amperage. Before changing the plug, check the voltage at the wall receptacle (also called a socket). Then call the kiln manufacturer and ask if your model can run on that voltage. Some kilns are designed to run on both 220 and 240 volts but, keep in mind, most kilns do not have this flexibilty.
Q. My Skutt Firebox 14 is about five years old but I haven't really used it a lot. The outside top of the cover is squares of firebrick, The cement lines are getting sort of sandy and I don't know what's happening. Should I worry?
Usually the cement between the firebricks lasts much longer than the firebricks themselves. As long as the firebricks in your kiln lid have not become loose, and dust from the cement seams hasn’t fallen from under the lid into the kiln, your lid should be okay.
The two elements in your 120-volt kiln are wired in parallel and the kiln has a 120-volt plug. To convert the kiln to 240 volts, wire the same elements in series, and change the plug to a 240-volt British plug. Ask for the 240-volt wiring diagram from Paragon, and compare it with the 120-volt diagram. Note the changes between the two diagrams. That will show you the difference between series and parallel elements. Unplug the kiln before working on it, and make sure the connections are tight.
Q. I have a big old kiln that has been a workhorse. When I turn it on, it starts running at full speed. The computer ignores any input. Any hope in getting it to work?
Q. I purchased an Evenheat HF 2318 at the standard 240V, but I am concerned we may have 220V at home. Does it matter? What would I have to do if it does?
If you are firing porcelain or stoneware, Low-fire ceramics might be okay but, I don’t think your kiln will get to full temperature on 220 volts. The only way to know would be to fire the kiln to find out. The HF 2318 is available in 220 volts, so you would have to change the elements to make it fire stoneware at that voltage. The real question is... are you sure the voltage is 220? Sometimes 240 volts drops to 220 during seasonal demand and then goes back up to 240 later. If your building should have 240 volts but is getting only 220, sometimes the power company will come out and change the transformer to raise the voltage.
Q. I've not fired my new kiln up and wonder how confident I can be in the pre-programmed programs that are keyed into the kiln. That is, how often do you think a new kiln owner like me will have to tweak those programs (for full fuse, contour fuse, etc.)?
The factory-installed programs in the controller are meant only as a starting point. Feel free to tweak them. Run a test firing. If a full-fuse program doesn’t get hot enough, program a higher temperature. Or, add hold time. As you gain experience, you will write your own programs. Keep a firing log book and record the results. If you aren’t happy with the results, figure out how to improve the firing schedule. Every time you successfully tweak the firing schedule, you will learn more about glass and your kiln. Many years ago, I called the Bullseye Resource Center in Portland for sample firing schedules to add to Paragon’s glass kiln manual. I figured that Bullseye knew as much as anyone in the world about firing glass. However, the teachers didn’t want me to publish firing schedules, because they didn’t want students to be disappointed if they didn’t all get the same results. Things have changed a lot since then as Bullseye now has a handy reference guide with suggested slumping schedules. My point is that every kiln is a little different, and results vary from one kiln to another. It is totally normal, and even fun to tweak firing schedules.
Q. I have 2 Paragon work-horses… Paragon Fusion 10 & Paragon CS-26. I was curious as the write-up I wsa reading noted replacing your thermocouple. I have never done this and have been firing my one kiln pretty much 1x a day for about 7 years. I've had no issues with firing, but should I consider changing this out?
The thermocouples in glass kilns generally last for many years. This is because the K-type thermocouple is rated to much higher temperatures than those needed for glass. I would not change the thermocouple if you are happy with the firing results.
Q. My RTC 1000 controller in my Olympic Kiln SQ146GFE isn't always working. When cold, the 3,6,9 & stop button doesn't work. When heated up, over 1000 degrees F, the buttons work. Makes it difficult to program.
The plastic overlay on your RTC 1000 should have a small gap between it and the buttons underneath. I would remove the four mounting screws, peel the overlay back, and try to use the buttons without the plastic overlay. You may need to increase the gap between the overlay and the keypad underneath or replace the plastic overlay. You can order another overlay from Bartlett Instruments at (319) 372-8366. If my suggestion doesn’t work, ask for engineering as they may have other ideas. I don’t think you will need to replace the controller.
Q. The bricks in the bottom of the kiln are crumbling apart. Is this something I can fix?
Firebricks are porous and fragile. In spite of supporting hundreds of pounds of ware per firing, they continue to perform for years. Nevertheless, they eventually develop cracks. This is considered normal wear. Have you ever coated the bottom with kiln wash? If you could send photos of the brick bottom, I might be able to offer additional suggestions.
Q. I have a Paragon GL 24 with crumbling floor bricks. I tried kiln cement and it looks worse. Can I replace the bricks myself? The kiln used to live in a humid environment. Would that have done it?
The humidity should not have caused the floor to crumble unless the kiln was in a flood, or it was in the rain. Sometimes applying cement to the firebricks makes the problem worse, because the cement has a different coefficient of expansion than the firebricks. This causes the cement coating to flake off in large chunks. Yes, you can replace the firebricks, but it's a big job that entails rebuilding the entire kiln. You would need to remove the switch box, top steel cover, the roof, elements, and walls. If you could you send photos of your brick damage, I might be able to offer suggestions.
Q. The side coils on my Jen-Ken EZ Pro are hanging out of slot. What is the best way to keep then in place.
Element shrinkage or expansion can cause the element to come out of the groove. The element comes out of the corner where two bricks meet due to shrinkage. It comes out in long sections due to expansion. The easiest way to put the element back into the groove is to disconnect the power, heat the bulging section with a propane torch, and shrink or expand the distance between the coils. The element will move back into the groove. Use needle nose pliers to shrink a section that is too long. Hold a section of four or five coils with the pliers and squeeze gently. The element must be red, or it could break. Use snap-ring pliers to expand a section of several coils. Once the element is in the groove, hold it in place with element pins. This is actually a very involved and needs much more detail than can be included here. This video might help... https://www.youtube.com/watch?
If the element in the lid stays on whenever the kiln is plugged into the power, then a relay has failed in the "on" position. The relay should be replaced.
Q. My kiln overheated and ruined my kiln sitter. Am I able to replace the kiln sitter with an electronic controller?
Yes, you can install a separate controller. The simplest method is to use an external controller. The kiln would plug into a receptacle on the controller, and the controller would plug into the wall receptacle that your kiln is now using. You would need to drill a hole in the kiln wall and install a thermocouple. However, it would be far less expensive to replace your Kiln Sitter. You may need only the porcelain tube and sensing rod.
Q. I have an Evenheat 2927DLT kiln that I bought from a previous owner. The previous owner had never used it and I found out why when I got it home. It was wired for a 440. My electrician rewired it for a 240 and I was able to use it at my studio in a shopping mall, but when the mall closed and I moved it home. I am trying to find a way to use this kiln. It is in good shape with a kiln sitter. Could I get an electronic controller that would work with a 240 and less than 10,000 watts?
Just recently I converted a 208 volt, 3 phase kiln to 240 volts, single phase. I installed new elements, a new cord set, and I changed some of the connections in the switch box. The Evenheat 2927 is available in 240 volts, single phase, so it can be converted to your household current, with or without a digital controller upgrade. You will need a new wiring diagram. Please call Evenheat for a list of necessary parts. A voltage conversion differs for every kiln model. The number for Evenheat is (989) 856-2281.