Notes on Glaze

Notes on Glaze

October 12, 2022

In 1972, when I was four years old, my dad, who was 42 at the time, left behind a career in architecture to get into the ceramics business. In the defunct Harlan Dramaware ceramic factory in San Clemente, California, he opened a ceramics manufacturing company called Artisan Kilns, which evolved into a more specialized glaze manufacturing company and ceramic manufacturing consultancy known as Miles Ceramic Color. In a pre-internet age, he taught himself everything about glaze in long nights of poring over books scavenged from libraries and used bookstores all over Southern California, in countless hours of glaze testing, and by picking the brains of mentors he sought out in the field at a time when Southern California was a hotbed of studio ceramic production and ceramic manufacturing. Fifty years later, at the age of 92, my dad still works at expanding his knowledge, and enjoys crunching numbers on glaze formulas down to decimal fractions on top of percentages. I have a sense of what it takes to become an expert on glaze at my dad’s level, and I’m not that by a long shot. But I picked up bits and pieces of knowledge working alongside my dad, and over the last twenty years I’ve worked at learning a lot more about glaze, with long nights poring over books just like my dad (and hours logged on the internet), through a whole lot of glaze testing, and by taking advantage of access to mentors including my CSULB colleagues Jay Kvapil and Tony Marsh, and most of all my dad.

I formulate, test, and batch almost all of my glazes from raw materials. I often start with upright, dependable, traditional “high-fire” glaze recipes and then mess with them—replacing some traditional ingredients with manufactured “substitute” materials or concoctions of my own; incorporating frits, stains, and other engineered materials; and tinkering with their balances of percentages—and then I put them in the company of other glazes to encourage them to break bad.

My dad always had an interest in layering glazes, and among the glaze test tiles and “chips” as he often called the glazed shards that could be found hanging out on just about every horizontal surface in our home, the ones that were the most intriguing to me were the ones with layered glazes. My dad enjoyed talking about how the glazes interacted, and when we were out and about, he would point out how the glaze application was handled on various things we saw.  Those conversations stuck with me.

I think of the glazes as ensemble players.  I’m always thinking of them in terms of how they look and behave as individual glazes and also how they will look and behave in combination with other glazes. They have roles: interior players, exterior layers, undercoatings, toppings or skins, runners, fluxers, oozers, blisterers, crawlers, cracklers, and other assorted cultivated hot messes.

In glaze books, some of my favorite pages are the ones devoted to defects, flaws, mistakes, and things you’re not supposed to do. I use oxide colorants traditionally employed in glazes, and I also use manufactured stains, and a lot of zirconium-crystal-encapsulated “inclusion” stains because they deliver intense color, hold up under high temperatures, and are less influenced or degraded by the presence of other materials. I test most of my glazes in both oxidation and reduction kiln atmospheres, but these days, I’m really formulating with oxidation in mind because that’s how I’m mostly firing the work.

Though I’ve long been focused on developing glazes for the higher end of the heatwork spectrum, usually firing to slightly in excess of a cone-10 heatwork measurement, and peaking at around 2350 to 2400 degrees Fahrenheit, just as I’ve recently been experimenting with lower-temperature clay body formulations, I’m beginning to work through potential low-temperature glaze formulas.