So much depends
upon
a red wheelbarrow
glazed
with rain water
beside
the white chickens—William Carlos Williams
At its core, glaze is a suspension of minerals that, when fired, bonds with the clay body to form a unified surface. Both glaze and clay are composed of minerals—silica, metal oxides, and fluxes—each of which reacts differently under heat. As the glaze melts in the intense heat of the kiln, it doesn’t just coat the surface; it interacts with the minerals in the clay itself, fusing into a singular, transformed material. This chemical interplay creates variations in color, texture, and sheen, sometimes pooling in recesses, sometimes breaking over edges. Beyond its aesthetic role, glaze can enhance durability and, in many cases, seal the clay to make it food-safe.
Glaze is a paradox. It enhances and obscures, protects and transforms. It makes a surface gleam with light while also softening and veiling what lies beneath. In this way, it is kin to glass (with which it shares an etymological root), which can act as a window, allowing us to see through it, or as a mirror, reflecting light back at us. Potters have worked with glaze for thousands of years. Still, despite its long history, it remains an unpredictable, almost alchemical part of the ceramic process—something to be both embraced and feared.
This unpredictability is what draws many potters to glazing in the first place. For some, glaze is a way of adding depth and complexity, building layers that shift with light and texture. For others, it is a more integrated part of form itself, something that interacts with material and fire rather than simply resting atop the clay. Some potters emphasize control, carefully orchestrating how the glaze will behave; others leave space for spontaneity, letting chance and movement shape the final result.
Glaze as Process, Layering, and Material
Some potters work with glaze as a means of building depth into their surfaces, layering materials to create complex interactions of color and texture. "Once I have a form I like, I tend to do an extensive underpainting," says Juli Kirk, describing her use of slips, terra sigillata, oxides, and transfer drawings. But after bisque firing, she applies glazes that partially obscure what lies beneath, using wax resist to allow selected details to emerge. Rather than using glaze to impose imagery onto clay, she works with the material itself, allowing depth and surface interaction to take precedence over representation.
Others, like Andy Vlock, see glaze as an extension of material rather than a separate layer. "Glazes are a wonderful opportunity to showcase material and tell a story," he notes. Sometimes, this means leaving areas unglazed to make the transition between materials feel uninterrupted. Other times, it means embracing movement—"Moving quickly while glazing allows for happy little coincidences to appear on every part of a piece."
Josh Kopin, whose work engages deeply with surface as both a physical and conceptual phenomenon, takes this further. "The surface of a thing is where it ends and also where it begins," he reflects. "Giving an object a surface is to gather and connect and form its parts in such a way that it develops a stable point where it stops and the rest of the world continues." The interface between glaze and clay is not just a finish; it is a moment of transition between material and space. A pot’s interior is a surface, its foot is a surface, and sometimes, even a surface can function as a handle.
The Ecology of Glazing: Materials, Networks, and Exchange
Glaze is not only shaped by an individual potter’s choices—it is also deeply tied to the environment, available resources, and craft traditions that surround it. Richard Wilson, in Inside Japanese Ceramics, notes that "the traditional Japanese potter made glazes with local ashes, clays, and stones, either alone or in combination." These materials came from kilns, hearths, farms, and even other crafts—indigo dyers, for instance, would extract lye from hardwood ash and pass the solid remains on to potters. The act of glazing, then, has long been an exchange between disciplines, landscapes, and histories.
This interwoven craft network continues today. Andy Vlock has sourced corn ash from withered stalks, scrap wood from a local guitar maker, and other byproducts that connect his firing process to the larger material world. The glaze on a pot may seem self-contained, but its composition often tells a story of collaboration, adaptation, and discovery—a reminder that no glaze exists in isolation.
The Balance Between Practicality and Experimentation
For all its aesthetic potential, glaze is also a functional decision. "Glaze determines the piece’s practicality and appearance," Ayumi Nojiri explains. "The best is both, but sometimes I have to give up one of these—like I can’t apply a non-food-safe glaze on my dinnerware, even if the glaze is beautiful."
Some, like Ayumi, return to their trusted, familiar glazes after testing out new ideas. "Sometimes I get bored using the same glazes, so I go on some adventures—but too much adventure brings results I don’t like, so I go back to what’s comfortable." Others lean into the instability of glaze as a creative force, finding beauty in the unexpected. Andy’s feldspar yunomi, for example, features a glaze of feldspar, wood ash, and river sand, where the unmelted silica left a rough, cave-like texture inside while the outside remained glossy and runny. Juli’s sawdust-fired pieces take this a step further, using no glaze at all—letting fire itself create the surface treatment as carbon seeps into burnished terra sigillata.
Josh, in contrast, explores how sheen and translucency create depth. "A glaze can have the revelatory power of water on stone, darkening the surface so that it glistens and reveals itself magnificently to the light," he notes, quoting Max Waterhouse. Glaze, in this sense, is more than just a final layer—it is a lens through which we experience form.
Letting the Arrow Fly
None of these potters work with an imagined end-user in mind. Their choices are not dictated by marketability or the preferences of an unseen audience but by their own dialogue with material, form, and fire. Josh describes glazing as a moment of surrender: "I dipped that cup quickly at the end of a long day, after my mind had shut off. And somehow, it came out beautifully—I didn’t touch it too much, and it was able to just become itself."
This insight recalls something Julio Cortázar once observed: “A true author is one who stretches their bow to its full extent while writing, and afterwards hangs it on a nail and goes to drink wine with their friends. The arrow speeds through the air and will hit the target or not, as the case may be, only imbeciles will try to alter its course and give it extra shoves.”
Like the archer, the potter refines their skill, makes their decisions, and then entrusts the rest to the kiln. The materials, and the heat, will have their say. And what happens after the pot emerges—how it is used, how it is understood—is beyond their control.
An Infinite Conversation
What makes glaze so fascinating is that it refuses to be pinned down. It is shaped by clay body, application method, firing conditions, and sheer chance. Some potters, like Juli, use it to build up layers of depth, while others, like Andy, let it merge into material and motion. For Ayumi, it is a practical consideration as much as an aesthetic one—an extension of how she imagines she’d like to use the pot she is making.
Josh’s thoughts remind us that surface is not static—it is a process, an event, a site of transformation. In his words, "Is a surface an enclosure? A veil or a window? A grate or a mesh? Consider that at the surface of water, vapor constantly condenses and evaporates in a process of exchange. The surface of water is stable in position but not material. Isn’t your surface also a process?"
Even across these different approaches, one thing is clear: glaze is never just glaze. It is a collaboration between maker, material, and fire, an unpredictable interplay of control and surrender. It is, in the end, a kind of conversation—one that is never quite finished, and that we continue every time we pick up a pot, run our fingers over its surface, allow associations to arise, and wonder how it came to be.