Heat-Pt 2-That's Hot...

Talking about heat, can be a controversial subject. First, this proves that ceramicists need new hobbies; second it is quite a ridiculous thing to be defensive over. I know that heat, it tied into one’s own ceramic identity. Now, some of you may say that I am exaggerating, but I have gotten in screaming matches over temperature.
Are you making Porcelain or Terra Cotta, Pit or Tunnel Kiln, Pristine Gloss or Raku, the temperature we work at defines our work almost more then the clay itself. I’m not here to say that this is not how it should be, temperature is important, temperature is imperative. But as with all things, temperature is not what we think it is.
What is heat? We talk about cones, we talk about temperature; we talk about Gas and Elements. I’m speaking of the Heat itself. Heat doesn’t care about its fuel or kilns that contain it. In fact, a kiln has nothing to do with firing the work; a kiln is a box meant to contain heat. Heat is the result of combination of fuel and oxygen combusted or electricity and resistance. That’s it. In fact, fire as we know it is just a byproduct of combustion, there’s no fire in an electric kiln is there? Why? No fuel.
So what is this heat then? Heat is the reflection of expended energy. The same way, when you work out, you expend energy. Your body consumes fuel and puts out performance. Heat is a byproduct. For us in ceramics, that byproduct is a very handy one.
When you took chemistry in High School, your best friend (or worst enemy) was the Bunsen Burner. This nasty little device (I had a fight with one once and still have a scar on my wrist to show for it) is responsible, for providing heat for the class. You see heat is imperative to the chemical process. Much like cooking, you really need to apply heat to get things moving. Admittedly there are some applications where you don’t need heat (Raw Sodium +H2O or Sushi). But for the most part, you need heat to get chemicals to do their little dance of love.
I bring up chemistry class very specifically. I have ranted before on this blog about chemistry, but let me state this again. When you are involved in ceramics you are committing acts of chemistry. End of Story. If you don’t like it, then you are more then welcome to take a long walk off a short pier. It is these acts of chemistry that allow us to do what we do. Chemistry makes clay and glazes.
Anyhoo, back to heat. So this all leads us to the notion of the temperature. Of course temperature is just the reflection of the volume of heat. But temperature is important to ceramics. The notion of progress is based in our ability to generate greater and greater temperatures. Starting at least18,000 years ago according to recent discoveries. Man put clay in a fire, that made the clay hard and (relatively) rugged, Ever since then, the study of ceramics has been “How do we make this more rugged?”
Well jump forward a bit. Eventually people figured out that you needed to get clay hotter then normal fire could produce, and the kiln was developed. This allowed for higher and higher temperatures to be generated, because as stated earlier, a kiln is just a box for containing heat. And the temperatures were getting higher and higher, and it was good.
Then they hit a wall…

NEXT TIME on SLIPCAST BLOG!
Europeans prove that they are not all that smart, and China enters the game, Kicking Ass and Taking Names.
Join us, Same Clay time, Same Clay URL.

Heat-Pt. 1-Cones

I have been pondering what I want to do about the topic of temperature for a while. At first I thought about talking about specific temperatures (Cone 6, Cone 3). Then I realized that there is an elephant in the room. That is the very notion of heat. We take the concept of heat for granted, we declare temperature (04, 6, 10) and then sort of leave it there. But heat is a very complex and difficult subject, it is defined by history, functionality and ceramics science. With that in mind, today I start an ongoing series on the subject of heat.

To really talk about heat we need to talk about history, unfortunately I know that is not a very sexy subject to start off. So I'm going to start in the middle (not to worry, we'll talk about history next). So, where I want to start is Cones. We treat cones as gospel, yet, can anyone tell me why Cone 10 is cone 10? Or why Cone 10 is 2381F/1305C? Or do you know why there is the Cone 01/1 divide? Does anyone know why we have all the problems with cones? It all seems a little random doesn't it?

Well, it all goes back to color, before pyrometers and cones, the only way we had to monitor temperature. It is a great method, in fact some of the more accurate temperature measurement devices today are optical, monitoring the color of the furnace. Reading temperature by color is a relative (and dangerous) pursuit. So alternatives were sought.

Enter Herman Seger. Seger is a really important person in the history of ceramics, we was a German Ceramic Scientist who lived from 1839-1893. He was a prolific thinker and inventor. and published 170 papers, so many he started his own journal.

In 1886 Seger published "Pyrometer and the measurement of high temperatures with standard cones". If you are in Europe, cones today are Seger Cones (opposed to Orton in the States). In this paper, Seger laid out the entire foundation for the modern ceramic temperature (Along with glazes, but that is a whole other subject). What Seger had discovered what that there is a relationship between Chemistry and Temperature. In that, when we apply heat to materials their reaction is based on the amount of heat used, and the composition of the material.

I'm going to do something now that is going to piss a lot of you off. But it literally has to be done, there is no way around it. I am going to talk about the Unity Molecular Formula (Or Seger Formula). If you don't know about the UMF, unfortunately I am not going to explain it here (Maybe later, but not now). The reason I have to talk UMF is that it is the basis for Seger's work and cones to this day.

What Seger realized is that by incrementally increasing Silica and Alumina level, there was a increase in representative temperature. So to say. A cone with a composition of 1.0 Silica and 0.1 Alumina (0.3 R2O:0.7 R0) would soften and bend at "Cone 1" And a cone with a composition 2.0 Silica and 0.2 Alumina (0.3 R2O:0.7 R0) would melt at a higher temperature (Cone 2, who would have guessed it?) This system is constant.


So on and so forth. That is why when we look at a cone chart, the temperatures seem random. They are reflections of the temperatures at which chemical reactions happen, and not an arbitrary round number.

Notice one thing, If you know your UMF you will notice that they look exactly like Cone 10 UMF Glaze numbers. That is exactly right. What cones are, is glaze, in dry cone form. Cones are just glazes have aren't fully melted yet. The bending and softening is the begging stages of glaze melt.
Also, notice that I started with Cone 1. The fact is that Cone 1 is Cone 1 is because it was the limit of the chemistry and the materials. To get lower temperatures, an entire new system on top of this one, had to be developed.

I think that is enough for today. I hope everyone found this informative, if you have questions please ask in the comments, and tell your Friends and spread the post around.