|Monthly Tech-Tip |
A test kiln is a must for all potters and small manufacturers, even serious hobbyists. Here is why.
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A test kiln is a small kiln having the ability to fire to the temperature and firing schedule of your production kiln. It uses on a fraction of the energy. A shelf in a test kiln, the heating of which takes most of the heat-up energy, might weigh 1kg (or as little at 500g if you make them yourself). Even a half-shelf in a studio production kiln can weigh 8-10kg. Test kilns can fire in a fraction of the time and the controllers on modern devices are amazing.
A test kiln is a must for all potters and small manufacturers, even serious hobbyists. When people are first caught up by the magic of ceramics, they are just happy to make a vase or bowl that does not fall down on the potters wheel or crack on drying. But the charm wears off quickly when large kiln loads of ware are lost due to inexperience, mistakes or unfulfilled expectations with a body or glaze. Later, when customers return ware that is crazing or leaking or leaching or cutlery marking, you will to continue can really be tested!
You may be taken aback by the price, but weigh that against what such a device can deliver. A test kiln, more than anything, determines where your ceramic knowledge and ability will be in a year. Five years. People who only have a production kiln do few tests. Why? Because most tests are failures, in larger kilns that costs money and time! Ability to test things is the principal enabler to your improvement as a potter. Having a test kiln is not an "extra cost", it is the "first investment" in making you independent and unique, it is the key factor in greatly increasing the success-rate in the production kiln you may later use.
People with test kilns commit themselves to think more about the technical aspects of ceramics. They learn why things happen. They are likely to be interested in how functional and durable their ware is. They are not taken in by the trafficking in recipes. Those pictures with the recipes might look flashy but they seldom work because the author does not include critical detail on making them work and the author likely does not have a test kiln! People with test kilns are more likely to know about what bodies and glazes do at higher and lower temperatures that the one at which they fire. They know about things like vitrification, density, firing shrinkage, thermal expansion, glaze fit. All by actual experience in firing tests. They are more prone to think outside the box, to dream and test the dreams. They see more clearly the infinite universe of techniques and materials that is ceramics. A test kiln makes you independent, able to utilize local materials or mix-your-own own instead of buying premixed. The ability to test will enable you to work at lower temperatures, where more testing is required to find success. It will enable you to develop the ceramic traditions of the area in which you live. Or to experiment with crystalline glazes, translucent porcelain, frit ware, engobes, decals, bone china, agate ware, porcelain jewelry, fast-fire, and more.
Having a test kiln will enable you to accomplish something few other potters do: Work at multiple temperatures. You will look back at working at one temperature as restrictive, primitive. Or energy wasting if you fired middle or high temperature. Even the ability to fire certain glazes or bodies one cone higher or lower can greatly improve ware quality.
If you make small pieces a test kiln can be a production kiln. You can even develop a fast-fire process that enables firing it multiple times a day. Coupled with a plaster table and a good propeller mixer, you could be independent and develop and produce a totally unique type of product. If you make high-value pieces a test kiln could be a far more practical production device. Our ConeArt 119 can hold 5 mugs so even some functional ware can be done. Considering that many test kilns run on 110 volts, the true practicality for a small scale manufacturer at home can be seen. Imagine what could be done in 3D printing custom-shape refractory setters, this could really maximize the use of the space for a production purpose.å
Every potter should have one of these. This one has a Bartlett Genesis electronic controller, you will never go back after having one. Start with a kiln like this and then graduate to having a large, second kiln. We have done 950 firings on this one in the past few of years, it is still like new. Ongoing testing is the key to the constant development of your products and their quality.
The red controller on the right is a Skutt Kilnmaster, the blue controller to the left is an Orton Autofire. As of 2022 both of these are now ancient devices, having been replaced with newer touch panel units. The principle of operation for both is the same: They turn the power on and off in a duty cycle to control temperature rise. A 50% duty cycle, for example, sees the power on for 50% of the time. The length of individual bursts increases with kiln temperature. The controllers monitor a thermocouple in the kiln to determine the length and frequency of power bursts needed. Both of these devices are external to the kilns (but there is a big difference). The KilnMaster controller is attached to the 220V power line and the kiln power line attaches to it (there are heavy-duty electrical relays inside). The blue Autofire controller does not have internal heavy-duty relays or switches, they are in the kiln. The KilnMaster is thus more flexible since it can connect to any kiln, but it is also triple the price. In 2022 the AutoFire now has its own relays like the KilnMaster.
This is a ConeArt 119D, 0.57 cu ft, 11"x9" cone 10 test kiln. While there is 120v model, don't take a chance, go with 220v (actually ours is 208v). Ours fires 1000 times on a set of elements, mostly in the cone 4-7 range. The old BX controller is shown here, it is $300 cheaper, but don’t even think about getting that! Do not use your electric like a pop up toaster, make it a technological enabler of custom firing schedules, get the Genesis GX. Having good control of firing is a key to success and this is superior for that. These kilns are economical to fire. Big enough for 5 mugs, but I typically fire a dozen clay and glaze test specimens. We make our own super-thin shelves. The controller holds about 20 schedules, even controllable remotely (it is Wi-Fi connected). We can fire cone 04 up and down in three hours! Of course, since this type of kiln can enable so much more testing you also need a code numbering system and a place to record and search all the results: An account at insight-live.com.
Very well endowed with elements. From the back view you can see how simple the wiring is on a kiln like this.
Imagine if you had everything for production at home during Covid-19
Brick-making is surprisingly demanding. Materials blending and processing, forming, drying and firing heavy and thick objects as fast as possible are like no other ceramic manufacturing challenge.
|By Tony Hansen|
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