Triple Glazing: Acknowledging Inspiration and Chasing the Image

Double-faceted cup, 3½ in. (13 cm) in height, triple glazed, fired to cone 9–10 in reduction in a gas kiln.

In December 2003, Ceramics Monthly published my article, “Carrying the Empty Cup,” which shared the words of three Japanese masters as they reflected upon how they learned and taught.

Shiho Kanzaki spoke about learning and inspiration in this way, saying that he would sometimes begin intentional learning by examining pots, or images of pots, that he found interesting. He would view a single piece continually for two days. If after two days of constant looking, he was still fascinated with the piece, he would measure it as a piece worth learning from.

After this initial, concentrated period of looking, Kanzaki would not look at the piece for at least one year (nor would he try to make a piece that was inspired by this work for at least a year). Instead he would let the image of the work, and his own imagination, begin to mature in his mind. He describes this process as “chasing the image.” The image would begin to change as it integrated into Kanzaki’s heart, soul, and spirit. As the image changed, Kanzaki continued to chase it. Over time, it became his own, not so much resembling the initial form, but having been distilled into something of the spirit of the initial piece—having been flavored by his own spirit. And thereafter, as the making eventually began, the chase continued. The works themselves began to inspire a new round of chasing.

Recently I realized that I have been in the middle of chasing the image. While I have been participating, almost unconsciously, in the chase for almost three years, until recently it hadn’t occurred to me that this was happening.

Six years ago, Chad Hartwig, then a research associate at the University of Notre Dame, near South Bend, Indiana, gave me a parting gift as he readied for a move to Minnesota. I remember it as a cup with blues and aquas, and perhaps some yellows. In my memory of it, there seemed to have been some kind of stable microcrystalline glaze applied first to the pot, followed by the application of one or two more glazes, after which it was soda fired.

I was so moved by the piece, so envious of the piece, that after a few days, I put it back in its packaging and onto a shelf in the basement. I felt afraid that if I kept looking at it that I’d be overly inclined to copy it. I couldn’t bring myself to do that to Chad, or to myself.

1 Bisque-fired cup, glazed, frit dusted. Shown prior to the glaze firing, as it would be loaded into the kiln. An extra pot sitter is placed in front of the cup to show the points of contact that support the cups.

2 Double-faceted cup, 3¾ in. (10 cm) in height, triple glazed, frit dusted, fired to cone 9–10 in reduction in a gas kiln.

The Chase

After two years without ever getting the piece out to look at it, and without ever having made a purposeful pursuit of the pot I so admired, it suddenly occurred to me that something about the essence of Chad’s cup had mysteriously distilled in my mind—without my even trying. I felt motivated to try to do something with this distillation. Alongside that, my interest in making pots with more vivid colors had been integrating into my aesthetic. When I realized that I was holding these two urges, I decided to commit myself to a major series of glaze tests in January of 2017. I was looking for glazes that had one of three qualities: stable microcrystalline glazes that could be fired to cone 13 without running or losing their matte qualities; cone-appropriate (I fire to cone 9–10) glazes with lots of color; and finally, colorfully complex glazes that melted at about cone 6 or 7. I even tried breaking the rules by testing a wide range of glazes that were designed for crystalline-glazed porcelains—glazes that begin melting quite early and were designed for oxidation firing atmospheres.

I began with 200 test glazes. After 6 months of continued testing, I culled the number down to about 3 dozen that had the colors and properties I assumed would be needed. I was hoping that my triple glazing would produce fluid, complex colors that would generously accentuate my significantly altered forms.

From there, and during the next year, I began the triple-glaze tests: three glazes on each large test tile, beginning with the stable microcrystalline glaze, followed by a layer of the cone-appropriate glaze, and finally a layer of the cone 7 glaze. This exploration produced far too many possible combinations, but I worked somewhat intuitively with 100 triple-glazed combinations.

Repeated testing with varying glaze application allowed me to bring the number of most frequently used glazes to about 15, which produced roughly 20 triple-glazed combinations that I found the most attractive, most repeatable, and least likely to obscure the altered surfaces of most of my pots.

3 Side-fired ergonomic cup, 4½ in. (11 cm) in height, soda fired to cone 13.

4 Chad Hartwig’s cone-10 soda-fired cup, which is very similar to the piece that originally inspired me. You can see the original inspiration in this piece, yet note how far from this piece my glaze-chasing took me.

Facing Problems and Finding Solutions

It was time to begin testing these combinations on real pots. As is my practice, I always start using new glazes and combinations on small pots, in my case 8-ounce double-faceted cups. It became almost immediately evident that the glaze load associated with the application of three glazes on a single surface, plus the addition of cone-7 melting glazes, would produce lots of running and dripping, an unacceptable amount for firing on good kiln shelves. And there was also the problem of getting the fired pots off the shelves without ruining them.

To address these problems, I reached back to some of the methods I’ve employed over my years of wood firing. I made a press-molded pot sitter for each piece. They look like small cookies with a few sharp points of clay sticking up. These minimize the amount of contact any pot has with the substrate. For example, the foot of a pot has roughly 100% contact with the shelf it fires on. Pot sitters reduce the contact to 3–5 tiny points that support the pot. When there is glaze running onto the foot of a pot, it continues down onto the pot sitter, leaving only small areas that need to be addressed post firing. In my case, I cut off the pot sitters with a wet-tile saw, and use diamond grinding and polishing tools to smooth the entire foot of the pot.

Of course, glazes that run down beyond the pot sitter will fuse the pot sitter to the shelf. To address that problem, I wad each pot sitter using wadding one might use in wood, salt, or soda firings. It’s lots of extra work, but it allows me to pry the pot sitter off the shelf and then move to immediately separating the pot from the pot sitter.

But what about the shelves? Fortunately I had some very old silicon carbide shelves that were no longer flat enough to use for normal production, which were sacrificed to the cause. After a triple-glaze firing, I pry off all the pot sitters, knock off any remaining wads, then use a diamond grinder to make the shelf relatively smooth, but not necessarily glaze free, because the next firing is going to create the same mess. For the same reason, I don’t bother with kiln wash on these old shelves. (Some potters cut thin pieces of insulating firebrick to place under pieces prone to running glaze. The firebrick acts as a sponge to catch errant glaze and separates pretty easily, but needs to be regularly replaced. Otherwise, individually made clay catch basins could be used if old shelves are in short supply.)

5 Teabowl, 4½ in. (11 cm) in height, triple glazed, frit dusted, wood fired to cone 9–10.

6 Teabowl, 4 in. (10 cm) in height, triple glazed, frit dusted, soda fired to cone 13.

Continuing the Chase

After having addressed these problems, I began firing real pots in earnest. After several months of successes, I began to critique the ways in which the pots were still missing the mark of my chased expectations. Mainly, I found myself wishing for a little more fluxing on certain parts of the pots. To address this, I began to use a sieve to do some isolated sifting of additional fluxes onto the pot when it was still wet from the application of the third glaze. To date I’ve tried sifting borax, lithium, and a wide range of Ferro frits (my current favorite is #3134). What I’ve learned from sifting fluxes has started me sifting well-mixed dry glazes onto still-wet pots. I’m not far enough along on my exploration of sifting dry glazes to make much of a report here—only to say that sifting dry glazes produces different effects from traditional wet applications. And a reminder to us all that dry sifting of any ceramic material requires appropriate safety measures in the form of working in a well-ventilated area while wearing gloves and a properly fitted respirator, as well as thoroughly cleaning with a damp sponge following the glaze process.

Three years after beginning my serious series of glaze tests, I’m still at it (200 tests and counting). I’ve expanded my firing methods beyond cone 9–10 gas reduction to include wood firing and soda firing. I’ve not yet pursued cone 9–10 oxidation firing or salt firing, but I’m sure there’s a treasure trove to be found there. Most of my initial results are only partially explored. I think that I have a lifetime of possibilities ahead of me as a result of those 200 test glazes.

7 Double-faceted pouring piece, 6 in. (15 cm) in height, frit dusted, fired to cone 9–10 in reduction in a gas kiln.

If you are still reading this article, you are likely wondering: Where is the photo of the pot that inspired all this research? When Ceramics Monthly asked for an article about my triple-glazing approach, I decided it was time to open the box and look at the pot, now 6 years later. But, odd as it seems, I could not find it. It has simply disappeared.

Maybe it’s a fitting end to the story: being inspired by the memory of a pot that no longer exists—how odd is that? It may attest to the power of chasing the image. I phoned Chad to tell him about the curious ending of this story. His words were an interesting addendum: “When I was making the pieces in that series, I was being very self-conscious about not letting the results of the firings dictate what I did next. I was trying to move forward with what I was doing, letting go of what I had already made, and not looking back. For me, the memory of what I was pursuing was better and more productive than the pieces themselves. Chasing what was in my mind was more valuable than what I was holding in my hand.”

Chad remembered exactly what he had gifted me, and offered to send me a second similar piece so I could share an image of it in this article. Seeing it, I remembered more clearly the piece he’d first gifted me, and was amazed at how far from his pots mine had ended up. It may attest to the benefit of allowing ourselves to be influenced by the fine work of others, while chasing the image with all our heart, soul, and spirit (as Mr. Kanzaki would say) to our own destinations.

Triple-glazed dancing bottle, 11 in. (28 cm) in height, fired to cone 9–10 in reduction in a gas kiln.

Developing Glaze Tests

My only true academic introduction to glaze development came in a second-year ceramics class at a liberal arts college almost 50 years ago. The assignment was to take a glaze that we liked, remove all the colorants, and substitute new colorants in their place. I think triaxial blends may have been mentioned. These two approaches were the extent of my formal glaze education.

Insufficient as it may have been, this has been my approach to glaze development over the years. It’s an easy way to make lots of tests, and I’ve become rather intuitive about it. Now, there are so very many resources at our disposal for coming to understand ceramics materials: books, in-person and online courses, workshops, glaze-calculation programs, and websites.

Even without a glaze lab, with the abundance of readily available commercially made glazes, triple glazing might even be easier. Simply purchase some glazes in your normal firing range, and consider selecting some that are made to mature at both higher and lower temperatures than your normal range. Think what you could do with just a dozen commercial glazes. Mathematically, you’d have 1728 different triple-glaze possibilities (12×12×12)—far too many to be manageable. Starting with half a dozen glazes would offer you over 200 possibilities.

When triple glazing, dip the second, then third glaze as soon as the pot is dry enough to accept more glaze. I recommend not separating subsequent layers of glaze by long periods of time.

The glaze combination used on the pots in this photo is Crystalline Blue applied to the entire pot as the first glaze, followed by Lehman Blue applied to the top 80% of the exterior, followed by Trout applied to the top 65% of the exterior. The pieces were fired to cone 9–10 in reduction in a gas kiln.

Triple glazing creates a significant glaze load on a piece. Too much thickness in each application of glaze may cause the raw glaze to crack and actually fall off the pot before/during firing. Too much glaze may actually cause most of the beauty to run off the pot during high firing. I’d suggest beginning by making the glaze a little thinner/more watered down than you might usually do. If you are used to thinking in terms of specific gravity (mass of a unit of volume) you may want to reduce the mass by adding water.

A better approach would be to begin by making a large enough test batch of each of the three glazes that you can measure specific gravity with a hydrometer. Begin by making all three glazes the same specific gravity as the thickest glaze you normally use. Triple-glaze a few test tiles. Add water to all three glazes and check specific gravity, then glaze more test tiles. Continue adding water and recording specific gravity until you are certain that the glazes are too thin. Keep good records. You should find that sweet spot somewhere in the middle. Use your intuition and dive in. Good luck!

the author Dick Lehman is beginning the slowing-down portion of his clay career. He’s actively practicing being a has-been, and is celebrating all the life and energy of the current generation of clay artists.

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