Kiln programming – what’s that all about?!?

When choosing a kiln for your glass work I would recommend investing in a digital controller. Many kilns come with simplistic controls. When working with glass, these are most often not precise enough to achieve the right results. Digital controllers are the best way to achieve the desired results. There are many different manufacturers and each controller will have manufacturer specifics that you need to be mindful of. However, the concept of annealing and firing are pretty similar so I will try to be a generalist about this as possible. I use the Perfect fire HDTP-56-55 digital controller; parts of this post will be specific to this controller as it’s the one I know.

Think of a firing cycle as a sequence of events much the same as baking. First you prepare the ingredients, then you combine the ingredients then you bake it at the exact temperature for the exact amount of time. It’s impossible to bake by mixing up this sequence of events, imagine baking the ingredients before you mixed them (the analogy comes from my recent endeavour to master muffins!). In any event firing cycles are the same. You have a sequence of events that must take place in order; this will give you the desired result.

Most manufacturers call a firing cycle a program. So in your controller you will have a program for bead annealing or a program for fusing glass, or a program for setting ArtClay silver. Each program is made up of its own unique sequence of events. My controller can carry a series of 55 separate segments. So I can specify 55 segments on my controller. Some controllers have no more than 8 segments available. What’s important here is to know which segments belong to which program.

For example I have Program 1 = Bead Annealing. This program consists of 4 segments. As it’s the first program in my kiln, when I want to anneal beads I start at segment one. The next program in my kiln is will thus start at segment 5 because the first 4 segments belong to Program 1 = Bead Annealing. Keeping a log of these programs and which segments belong to each program is paramount to managing your kiln effectively.

Some controllers come pre-programmed but I always advise to get to know your equipment. For example, I used my pre-programmed fusing firing cycle (starting at segment 32) for fusing last night. The program uses full power to get to the desired temperature 740°C which takes only 15minutes to get to that temperature. Because I had increased the dimensions of the sheets of glass I was using the full steam ahead was too fast and my glass could not handle the sudden shock of heat, the result? It exploded all over my kiln. So now I need to create a program that caters for a slower pace to get to the desired temperature.

Each segment consists of its own sequence of events. So basically the hierarchy of programming looks like this

Program (recipe) = Segments (ingredients) = events (stages of progress)

So each program is made up of segments. And each segment is made up of an event

Now we move onto events, this is where all the magic of firing is held. Having done research on various manufacturers I have found that for the most part they all use the same sequence of events.

I’ll try simplify firing cycles for you.

Quite simply from a cold kiln you want it to get hot, stay hot and then cool down. Sounds simple doesn’t it? So the process of:

– Getting hot = Ramping up
– Staying hot = Soak (NB for lampworkers, your beads must soak for at least 30mins after the last bead has gone into the kiln)
– Cooling down = Ramping down

My controller has 3 types of events that I use:

– Cont = continuous ramping until the desired temperature is achieved
o Ramp rate = time it must take to reach the desired temperature or °C per hour
o FULL = use maximum power to get to temperature as quick as possible

– Conr = Continue regardless i.e. heat up or cool down at the arte specified for X minutes/hours. When the time is reached proceed to the next event regardless of the temperature. Like ovens kilns can come varied some kilns are “hotter” than others i.e. they retain heat better by design. So even though you have set the kiln to reach 200°C in 2 hours, it may not be 200°C within the 120 minutes. Continue regardless means move onto the next event after the 120 minutes whether or not the temperature is 200°C

– End = self explanatory, the program has ended. If you do not have this segment at the end of your program then the kiln will move onto the next program so it’s paramount to have an end event as your final segment of each program

In practise:

Ok all fine and well in theory but how do we put it into practice? Let’s say I am about to start lampworking. I want to put my newly made beads into a kiln that is holding a temperature of 515°C which is specified for soft glass (COE 96 – 104). I want to make beads for about 2hrs after work. Then when my two hours is over and my last bead has gone into the kiln, rule of thumb states the bead must be in the kiln for no less than 30 minutes before cooling down starts. Because we are working with soft glass the rate off cooling should typically be an hour till reaching 200°C at which point the kiln will switch off. The Program, segments and events look like this:

Program 1

– Segment 1

o Event = Cont (keep heating until you reach temp required)
o Ramp Rate = Full (use full power to reach desired temperature)
o Soak time = 2 hours (I have 2 hours to add beads to the kiln)
o Temperature = 515°C (it will ramp at full power to 515°C and hold this temp for 2hrs)

– Segment 2

o Event = Cont (keep heating until you reach temp required)
o Ramp Rate = Full (use full power to reach desired temperature)
o Soak time = 30mins (hold this temp for 30mins after the last bead has been put in)
o Temperature = 515°C (it will ramp at full power to 515°C and hold this temp for 30mins)

– Segment 3

o Event = Conr (cool the kiln at the desired rate aiming for 200°C over 1hr)
o Ramp rate = 315 (515°C – 200°C=315; 315 /5.25°C = 60mins)
o Soak time =0minutes (once 60 mins at ramp rate of 315 is reached the next segment starts as defined by Conr)
o Temperature = 200°C

– Segment 4

o Event = End

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