PPP: Controlling Quality by Controlling Your Kiln

Today’s kiln controllers provide a high level of accuracy, repeatability and firing control in a user-friendly, affordable package.

A precise firing cycle, achieved through the use of high-tech controls, enables potters like Bill Campbell to precisely fire even difficult glazes. Photo courtesy of Campbell Studios, Cambridge Sprints, Pa.
Few production potters can afford high losses at the firing stage. But for anyone who is still relying on manual control for their gas or electric kilns, a significant number of losses is an inevitable part of making pottery. While tools such as pyrometric cones can help you measure the heat work in your kiln, they can’t make adjustments for you, and they can only alert you to problems if you’re watching them regularly. For potters with firing cycles of 20 hours or more, this means many long, sleepless nights and a lot of wasted time watching over the kiln. Additionally, if any problems do occur, chances are pretty good that you won’t be able to correct the problem in time to save the ware currently in the kiln. Fortunately, this situation can easily be avoided with today’s high-tech, affordable kiln controllers. According to Bill Campbell, a respected production potter and a long-time proponent of electronic control technology, using a reliable kiln controller can often mean the difference between success or failure. “A kiln controller enables you to fire your products right one time, understand what happened, and then be able to do it accurately again and again and again. There’s no point in feeding the dumpster—it’s better to feed your family. Today’s kiln controllers can help you achieve the level of quality you need to sell your products,” Campbell says.

Photo courtesy of Campbell Studios.

Gaining Control

Campbell first began using kiln controllers nearly 15 years ago, when they were almost unheard of in the pottery industry. “Controllers at that time were very expensive, and they were also complicated to program and use. But I had developed some blue glazes that had to be fired precisely to turn out right, and I couldn’t achieve the levels of accuracy that I needed by manually firing my kiln. I was losing close to 50% of what I was making to defects,” Campbell says. Desperate to reduce his losses, Campbell decided to invest $25,000 to outfit his 350-cubic-foot gas-fired car kiln with computer-controlled, state-of-the-art, high-velocity burners from North American Mfg. Co. “I was actually more interested in being able to buy some decent burners than I was in the controls,” Campbell admits. “The controller, which was manufactured by Yokagawa, came along as an extra when I purchased the new burner package. But it didn’t take me long to start noticing the benefits of the new system.” The new burners enabled Campbell to carefully control both the temperature and atmosphere inside his kiln throughout the entire firing process, and his losses dropped drastically as a result. But equally impressive was his newfound ability to let the kiln do all the work automatically, without constant supervision. “My kilns run on 26- and 27-hour cycles, so it took a lot out of me to have to watch the whole firing process,” Campbell says. “With the controller, I could program when I wanted the temperature to go up and at what rate, and I could tell the kiln to reduce at a specific time. I could tell it when to fire down and when to hold, and the system would follow this program very accurately. All of the sudden, I was able to walk away from the kiln and know that what I wanted to happen would happen exactly on time every time. Having a controller gave me my life back.”

The Next Generation

By the late ’90s, Campbell had begun using electric kilns to fire some of his smaller specialty products. Unfortunately, his first experience with electric kilns was less than ideal. “There were some problems with the heating elements, so the kilns wouldn’t fire accurately. I must have fired a dozen loads or more that were complete losses,” Campbell says. To solve the problem, Campbell again turned to control technology—this time through Bartlett Instruments and a software program called KISS™ (Kiln Interface Software System), which enables controllers on electric kilns to be programmed and monitored remotely from a personal computer. In kilns with multiple zones, the software allows each zone to be programmed and monitored independently. When a problem occurs in one zone, the software automatically adjusts the other zones to compensate. The software also provides the ability to collect and store data from the firing process, which allows for detailed evaluations of the kiln’s actual temperatures during a firing. The status screen shows the current program, set point, segment, firing time and zone temperature for as many as 10 different kilns. Firing information can also be collected in a file for later viewing or graphing. “With the KISS program, I began to really understand what was going on in those kilns and was able to easily correct the problems,” Campbell says. The capabilities of the KISS program became especially valuable in early 2000, when Campbell began using a new line of crystalline glazes. “The crystalline glazes produce beautiful patterns—but they require a long firing cycle of about 24 hours, including a precise cooling cycle of about 12 hours. Without a good controller, I wouldn’t be able to use these glazes,” Campbell says. Campbell currently fires his crystalline products in three electric kilns—two from Olympic and a newer elevator kiln from L&L Kiln Manufacturing Inc.—and all three are controlled through the KISS program. He also uses the program to monitor his three gas kilns. For Campbell, this means a high level of firing accuracy and easy troubleshooting if any problems occur. “With the KISS program, I can tell at a glance what the temperature of each zone is—or was—during each firing. So if something is wrong, or if a heating element is starting to wear, I can see that and make a repair before I lose a load of pots.” Additionally, unlike earlier generations of controllers, the software is designed to be inexpensive and easy to use. “Many of us potters are very visual people, and we’re not terribly technical. With the KISS program, you get a visual representation of your firing cycle on your computer monitor, and you can tweak it intuitively rather than trying to figure out a bunch of numbers. It’s also very easy to write and change the firing program,” Campbell says.

Fuzzy Logic and Other Advances

Controllers for gas kilns have also become more advanced and easier to use over the last several years. After purchasing his first controller in the late ’80s, Campbell has since upgraded all three of his gas kilns to next-generation models. “The nice thing about the newer generation of controllers for gas kilns is that they have ‘fuzzy logic,’ which essentially tells the kiln what to do, and the kiln does it,” Campbell explains. “If the kiln overshoots or undershoots where it’s supposed to go—for instance, if the burner stays on or off a little longer in a cycle than it’s supposed to—it will learn from its mistakes. Within a few cycles it will have learned exactly what it’s supposed to do and will stay on that ramp perfectly.” Today’s controllers are also much less expensive than conventional models. “A really sophisticated controller will cost around $1100, while less sophisticated models can be purchased for around $600. And with the benefits they provide, they pay for themselves very quickly,” Campbell says.

Controlling Your Life

As with any new technology, the benefits of using a kiln controller—even today’s most sophisticated models—aren’t necessarily instantaneous. According to Campbell, there is a learning curve involved. “When I purchased my first kiln controller, it did exactly what I told it to do—but I didn’t know what to tell it to do. As a result, my first few firings were complete disasters,” Campbell says. “I used a time-temperature recorder to record exactly what was happening in my other kiln, which was firing correctly. With that information, I was able to program the other kiln to do the same thing, and that’s when I started reaping the benefits.” With greater control over his firings, Campbell is able to concentrate on developing new products and other important pursuits. “I really believe that controllers are one of the most significant advances in pottery tools since the electric wheel,” Campbell says. “They give you a lot more control over your firing—and a lot more control over your life.”

For More Information

For more information about Bill Campbell or his company, Campbell Studios, visit www.campbellpottery.com.

For more information about Bartlett Instrument Co., contact the company at 1404 Avenue M, P.O. Box 445, Fort Madison, IA 52627; (319) 372-8366; fax (319) 372-5560; e-mail information@bartinst.com; or visit http://www.bartinst.com.

For more information about L&L Kiln Manufacturing Inc., contact the company at 8 Creek Pkwy., Boothwyn, PA 19061; (877) 513-7871; fax (610) 485-4665; e-mail sales@hotkilns.com; or visit http://www.hotkilns.com.

For more information about North American Manufacturing Co., contact the company at 4455 E. 71st. St., Cleveland, OH 44105; (216) 271-6000; fax (216) 641-7852; e-mail sales@namfg.com; or visit http://www.namfg.com.

For more information about Olympic Kilns, contact the company at 4225 Thurmund Tanner Rd., P.O. Box 1347, Flowery Branch, GA 30542; (770) 967-4009; fax (770) 967-1196; or visit http://www.kilns-kilns.com.

More information about kiln controllers can be obtained from pottery supply companies or kiln suppliers.

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