Category Archives: Glaze

Glaze, Technique

Pure nature: an Earth Crust Glaze

Leave a comment

Have you ever wondered what would happen if you ground up the entire earth’s crust, mixed it thoroughly, and then mixed it with water? Then you get… a ceramic glaze!

But how do you actually prove that? Of course, I could fire the mixture in a kiln at about 1280 °C to see what the result is. But how do you get a completely ground earth’s crust?

Fortunately, there is another way to show that a glaze based on the earth’s crust produces a shiny, deep dark brown ceramic glaze. You just have to do the math…

Continue reading Pure nature: an Earth Crust Glaze →
Glaze, Technique

Ceramic decoration spectrum in perspective: Slip, Engobe, Glaze and Wash

Leave a comment

Slip, engobe, glaze and washes are terms you often hear when you delve into ceramic decoration. These terms have always been a source of confusion for me, especially since different ceramists give them different meanings. A clear definition can help to bring order in the chaos. But even more important is gaining insight.

You can memorize definitions, but I’m happy to leave that to AI models. More important is understanding both the differences and similarities between these materials for ceramic decoration. In my opinion, it is essential to recognize that all of these decorating techniques are part of a continuum.

This continuum extends from slip, through engobe and glaze, to washes. Based on the amount of clay (the source for Al2O3) and quartz (SiO2) you can put this into perspective.

Stull Chart from 1912

This is easy to visualize with the help of the “Stull graph”. R.T. Stull made this graphic in 1912 to classify glazes. But also very useful to gain insight into the entire ceramic decoration spectrum.

Continue reading Ceramic decoration spectrum in perspective: Slip, Engobe, Glaze and Wash →
Glaze, Technique

Ceramic raw materials: calcining is nothing but hot air, LOI explained

Leave a comment

If you make your own glaze recipes, you use ceramic raw materials with hot air… or “LOI” for short. Sometimes this LOI is removed from the raw material beforehand by “calcining” it. But what exactly is that and why do ceramists do it?

By hot air, I don’t mean (this time) all the crap that bloated types spew into the ether. I’ll probably talk about that another time, but this time I want to talk about “Loss On Ignition” or the abbreviation LOI. In other words, the evaporation of substances by intensely heating them: calcining.

Let me explain using the raw material kaolin and a kiln that we will fire at 750 0C (1382 F). Time for an experiment!

Continue reading Ceramic raw materials: calcining is nothing but hot air, LOI explained →
Clay, Firing, Glaze, Technique

Top three reasons to buy a small ceramic test kiln (and one to get rid of it)

2 Comments

I recently purchased a small Rohde ceramic test kiln from Keramikos. In addition to congratulations on ” the little one” :-), I was also asked: why buy a test kiln? After all, I can also fire my work in my larger (150 liter) kiln.

glaze testing unfired

A good question and a nice reason to list my reasons for my investment in this blog. I came up with this top three and one to get rid of my kiln…

Continue reading Top three reasons to buy a small ceramic test kiln (and one to get rid of it) →
Firing, Glaze, Technique

More control over Glaze Firings? Use PTCR Measuring Rings!

3 Comments

PTCR measuring rings quantify both time and temperature of the glaze firing: heat work. Why do I think that’s so important to know (and to measure)? There are several reasons for this…

But let me start with what exactly PTCR measuring rings are. PTCR stands for “Process Temperature Control Rings”, so rings to get control over your firing temperature.

And what do you get out of it as a potter? I would like to explain that in this blog.

Continue reading More control over Glaze Firings? Use PTCR Measuring Rings! →
Glaze, News, Technique

Food safe ceramics: tightened EU laws coming up

11 Comments

Food safe ceramics and glazes is a complex subject. On this topic glaze technologists, toxicologists, artists, craftsmen, industrialists, lawyers and legislators meet. And I’m sure I’ve forgotten a few more. It’s also a subject I’m dealing with. Not as a glaze technologist, but as a craft entrepreneur.

A well-balanced glaze is not only durable, it is also safe for everyday use. As is my functional pottery, in EU jargon FCMs (Food Container Materials).

This means that my ceramics/glazes comply with the current EU directive ‘ceramic articles intended to come into contact with foodstuffs’. But these EU laws may soon be tightened.

What are the consequences for me and other artisan potters in Europe? I had an interview about this last week by two researchers on behalf of the European Commission for Health and Food Safety.

Continue reading Food safe ceramics: tightened EU laws coming up →
Glaze, News, Opinion, Technique

The best ceramic glaze book of the year

Leave a comment

What is the best ceramic glaze book of this year? If you ask me, that’s “Special Effect Glazes” by Linda Bloomfield. This is the first book that explains how to analyze (special) glazes using the UMF and plotting it on the Stull Chart. The author also explains how you can do this easily: by using Glazy.org.

This is the modern way to discover the “mechanism” behind the glaze. In other words “what makes this glaze tick“. She is not the first to analyze glazes in this way. Matt Katz of Ceramic Materials Workshop in particular is the driving force behind this contemporary view. But he hasn’t (yet) written a book about it.

Ceramic Glazes Test Tiles 2

In short, as far as I am concerned , this is the book to show 21st century ceramists the way to that new manner of discovering ceramic glazes.

Continue reading The best ceramic glaze book of the year →
Glaze, Technique

Are handmade ceramics dishwasher safe?

Leave a comment

Does the dream of surrounding yourself with handmade ceramics have practical objections such as dishwasher safe? To be beautiful, …uh.. use beautiful ceramics … means suffering?

Or better yet to quote the Dutch poet Willem Elsschot:

[…] for between dream and deed
laws  and practical objections stand in the way
(Willem Elsschot 7 May 1910)

Handmade ceramics in actionFortunately not! Handmade dream ceramics and dishwasher convenience do not encounter any practical objections. At least when the glazes used are properly designed and fired correctly.

Continue reading Are handmade ceramics dishwasher safe? →

Glaze, Technique

Arriving at glaze temperature

2 Comments

A ceramist wants to arrive as an artist, a ceramic glaze wants to arrive at the right glaze temperature. Greg Daly calls this “arriving at temperature” in his glaze travels. Who dares to say that there is no poetry in ceramic glazes?

Daly provides methods to investigate at which temperature glazes melt, but no (theoretical) tools to  predict this for a given glaze. However, you do need this if you want to design a glaze with a predetermined temperature. If you don’t know which corner to look in, it is also hard to get there.

Glaze temperature is a mechanism, as there are several in glaze technology. To be able to decipher this mechanism you have to look from the right angle (more about this in this blog).

For glaze temperature this is the oxide level. If we dissect a glaze into oxides (the different molecules in a glaze) it is possible to discover trends.

I am still researching how to arrive as an artist, but I have guidelines to arrive at the right melting temperature for any glaze. In this blog I explore the three main ratios:

  • SiO2 -Al2O3
  • RO2 -RO
  • B2O3
Continue reading Arriving at glaze temperature →
Clay, Firing, Glaze, Technique

3 Ceramics Mystifications Unmasked

Leave a comment

Making ceramics is magical, ceramics mystifications certainly are not. Ceramics and glazes are surrounded by a cloud of thick black smoke. And I do not mean the smoke when firing raku.

Copper Red EnamelTheory behind practice is often unnecessarily made very complicated. Because of ignorance, to impress? I have no idea, but it has always frustrated my quest for clear knowledge. Time for unmasking.

In this blog I grab three ceramics mystifications by the clay.. euh horns.

Continue reading 3 Ceramics Mystifications Unmasked →

Glaze, Technique

Ceramic glaze levels for analysis

Leave a comment

As a glaze nerd I like to make rows. That’s why I use the “viewpoints” of Tony Hanssen (digitalfire) when analyzing glazes. From him I learned four glaze levels:

  1. Process
  2. Recipe
  3. Material
  4. Oxide

Copper red glazeIn developing a glaze I have always had this theoretical framework in mind. I greatly benefit from this to achieve desired results, a finish that fits my ceramics.

In recent years more and more public data are available, also in the field of glazes. Can these new insights be incorporated into the existing framework or is it time for more perspectives?

Continue reading Ceramic glaze levels for analysis →

Clay, Glaze, Opinion, Technique

Commercial glazes, pushing product

2 Comments

This week a blog about a new book by Deanna Ranlett “Off the Shelf, outside the Box”.

Off the Shelf/outside the Box: A Guide to experimenting with Commercial clays, glazes, & UnderglazesI fasten my bike on the Bloemgracht, Amsterdam. On the corner I can score at my dealer, in an old building with a nice glass facade. I step in, my heart rate accelerates, my blood pressure rises. I can’t pull my eyes from all the mysterious powders in many colors on the shelves. Here dreams are fulfilled.

It was in the early years 90 of the last century. And no, it wasn’t a “headshop” where I went in. It was the old shop of Ve-Ka in Amsterdam. Of these powders you do not hallucinate, but you will be happy…… when it is fired in a ceramic kiln.

Continue reading Commercial glazes, pushing product →