“The Times They Are A-Changin'”, Bob Dylan sang in 1964, and that’s right: the ceramic kiln control has changed a lot in recent decades.
Maybe he wasn’t singing about ceramic kilns, but he certainly could have done it! Political climate and human nature may have changed little since the ’50s. But the way ceramists operate their kilns has evolved dramatically.
From a hole in the ground to an electric kiln, it was a huge technological leap that took thousands of years. However, the transition from manual to fully automated control has taken place in less than 50 years. Making it accessible to urban potters like me.
For me, Lucie Rie is the founder of all “urban potters”. Rather than setting up a studio in the countryside with a gas or wood-burning kiln, she established her pottery shop at 18 Albion Mews, in the heart of London.
She ordered her first real electric stoneware kiln in 1948. It soon became clear that firing was more difficult than expected: the first firing during Christmas failed completely. The kiln over-fired!
First ceramic control: the Kiln Sitter
Lucie Rie and her team had to operate the kiln completely manually, including determining the moment when to switch the kiln of. The get to the desired maximum, she had to observing when the cone fell. In her case, it was the Staffordshire cone 8, which reaches a temperature of about 1250 °C.
What she didn’t have at her disposal was an American invention from the early 1950s: the kiln sitter. This mechanical device automatically shuts off a manual kiln when a preset temperature is reached. The system uses a “cone” (Seger cone) of the desired temperature. This cone is placed in the kiln. When it begins to melt, the cone bends, which activates an ingenious mechanism (based on gravity) that turns off the kiln.
From the 1960s to the late 1980s, ceramists used this fantastic technological development to fire their ceramics at the right temperature.
Yet, It wasn’t a real ceramic kiln control. After all, until the top temperature was reached, the ceramist still had to manually control the firing speed him- or herself. Just like Lucie did in the 1950s.
How does a ceramic kiln work?
To understand how controlling an electric ceramic kiln works, it is essential to know how a ceramic kiln functions. A kiln is basically a box that retains heat. The ceramist can generate this heat in various ways, for example by burning wood, gas or oil. In a gas kiln, the gas is lit at the bottom, after which the flames are led through the kiln.
The firing rate, or the rate at which the temperature in the kiln rises, is regulated by the amount of gas that is supplied. This can be increased or decreased. In an electric kiln, the power supply is controlled in a similar way, but by turning the power on or off for certain time intervals.
In older models, this was done with a rotary knob or a universal switch. Depending on the position of the knob, for example on the lowest setting, the kiln was on for 30 seconds and off for 90 seconds. When the kiln turns on, there is an audible ‘click’ and on some models, a light is turned on. This is followed by a buzzing sound of the electricity. This process repeats with a ‘click’ when the kiln shuts off and the buzzing stops.
The control knob was turned up manually. When the power circuit is turned on (connected) or of (opened) there is a clicking sound. These ‘clicks’ are from the mechanical action of the magnetic contactor(s). And the buzzing come from the heating elements. These also begin to glow because of the current that flows through them.
By building in a series of two or three of these switches with a timer, you could even program steps in advance. The first real ceramic kiln control avant la lettre. Only for the happy few….
Ceramic kiln control, my experiences
In the not-so-distant past, thirty years ago to be exact, I operated my first electric kiln. The Ve-Ka R.SVK/40 O. Every morning I got up early, to personally turn on the kiln at 6 AM. That went fine, but my work wasn’t done yet. According to my own firing schedule, I had to turn the knob up a setting every four hours, until late in the evening.
The Ve-Ka kiln was a ‘semi-automatic’. It switched off electronically as soon as the top temperature, which I could set with a dial, was reached. This was already an improvement over the kiln sitter with its mechanical shutdown. Nevertheless, times were tough for me…
Of course, that couldn’t go on any longer 🙂 Fortunately, salvation was at hand with the arrival of the kiln controller, or the microprocessor as we proudly called it at the time. At the beginning of this century, I also bought one: the Bentrup TC507. I was able to preset the entire firing program from start to finish. The only thing that was left for me to do was turning on the kiln.
And of course, don’t forget, to fill the kiln with pottery.
Not all ceramic kiln regulators are equal
In the 1950s, Lucie Rie fired her ceramics in a kiln similar to mine. However, she had to manage the entire process manually: turning it on, regulating the firing speed during the process and shutting down the kiln in time at topt temperature. Fifty years later, I could turn on the kiln and then do something else, until the kiln cooled down 24 hours later.
Times have indeed changed, but it doesn’t end there. Over the past twenty years, developments have not stand still. Logging the firing process, online live tracking, error codes, SuperWise, solar ready, and so on. Not every controller is the same. What are the differences between the various brands and types? Are all functions essential or sometimes superfluous?
There is still a lot to discover about the regulators of ceramic kilns, but we will save that for the next blogpost.
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