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Can Potters Learn About Firing Gas Kilns From Industry?

Section: Firing, Subsection: General

Description

There is a big gap between industrial and studio gas kiln technology. Even the basic theory behind how to construct and file are different. Can potters learn?

Article Text

There is a saying that "experience is the best teacher but she charges a lot!" Experienced potters sometimes feel a bit smug about their ability to build and control a gas kiln because they paid a high price to learn. Firing our pottery kilns is a pretty personal and even emotional thing and industrial firing seems a coldly uncreative way to make good glaze and body surfaces. For example, reduction is not normally used in industry, even flashing is simulated with stains! However this gap between the worlds of industrial kiln technology and pottery kilns is quite educational.

Consider: Electronic temperature controllers on electric kilns are a fairly new development whereas industry has had devices that control atmosphere, pressure, flow, volume, and temperature for many decades. Burners with 250mph nozzle velocity and fire lanes over, around, and under the load don't impinge the ware and yet produce an active atmosphere that distributes and transfers heat to and from ware very efficiently. Interlocking kiln furniture creates a stable load and spotlessly clean settings assure defect free ware. Compare that with an almost complete lack of flow inside most electric kilns and flimsy furniture that would block any currents if they it did exist. In addition, while firing temperatures are repeatable, firing schedules are not. This is because the elements in these kilns deteriorate over time and thus they fire slower, the amount of heat-work done is different even though they might go to the same temperature.

Potters often adjust the proportions of gas with primary and secondary air using damper and burners according to color and length of flame. In industry they do the opposite, they maintain a constant volume of input air-gas. All air entering the kiln passes through the burner module which meters gas in a precise stocheometric 10:1 ratio (just enough oxygen to burn all the gas and maintain 1.5% oxygen atmosphere, normal pipe burners are about 7:1). Motorized dampers and exhaust fans maintain a constant internal pressure of (approx. +.02 inch water column). Actually this is not even true anymore, proportional firing has given way to pulse firing.

They can fast-fire (often in one hour) and produce defect free ware with very low loss. Maybe we can learn something from them after all.

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By Tony Hansen




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