CG: What was your first experience with clay, and what was it that “grabbed” you?
Thullen: I grew up in a house where handmade functional and decorative objects were ubiquitous. Reed Baskets, Ceramic Figurines, Cross-Stitch, Ukrainian Easter eggs, and a plethora of other meticulous, detailed objects were my everyday surroundings. The small electric kiln in our basement was the first introduction to clay, long before I even knew what it was used for. I was exposed to these objects from a very young age, but it wasn’t until my first experience with clay in Junior high school that I really understood the potential of the material. Or, the possibilities that it would open up for me to fill my need to make things with my hands, and in some way, shape my own surroundings.
CG: You are both prospecting glaze materials, yet very differently from one another. What is your approach to prospecting, and how has it changed since you began?
Thullen: My interest in working with locally sourced materials began years ago when I began working with atmospheric firings, and started looking into more traditional, historic methods of creating glazes. After spending so much time testing and experimenting with traditional reduction glazes, I was ready to move beyond the conventional “crayon box” of the materials that I had at my disposal from ceramic suppliers, and to see what could be achieved with materials sourced from my own surroundings. This began with more conventional choices akin to the material that were used by early potters to create their glazes, such as wood ash, locally dug clay, and numerous materials derived from traditional geological sources, and the landscape around us. I was interested, as I began to develop my own personal aesthetic, in carrying this idea through to my glaze materials and palette as well.
More recently, I have begun what I refer to as “Urban Prospecting”. In thinking about the process of sourcing my materials and how this related to the work that I was making, I began to consider the source of my aesthetic. I am heavily influenced by, and interested in the application of ceramics to architecture. The patterns and texture used to decorate my pots began by looking at pattern and geometry in architectural embellishment and decoration, including brick, tile, and other uses of ceramics in constructing our environment.
I started to realize that I could be using these materials themselves physically, and not just as inspiration, by processing these materials to create my glazes themselves. Additionally, in thinking about the origins of my materials, we all derive sourced material from our surroundings. Living and working in an Urban (and suburban) environment, I don’t have landscape or geology readily at my disposal. My landscape is the urban environment that I work in, and drive through every day. This is where I have begun to draw from to create my glaze palette. The materials that I use are essentially the detritus from Architectural and Industrial sources in my surroundings. Old building bricks, broken glass, industrial slag, and chunks of concrete contain the necessary chemical makeup to make glazes just as beautiful as any that can be derived from the rocks and minerals that shape the natural world around us.
Specific Glazes I Use:
Clay Bodies: I use a very simple porcelain body, mainly Kaolin, Feldspar and Silica and a few small additions for workability. This is the basic clay that I use to make the majority of my pots. Three of the pieces in the exhibition are made with an iron-rich version of this clay body that contains Iron-rich slag which I found on a beach in Northern Michigan last summer. The clay body has such a high thermal expansion and contraction rate as a result of the iron that only my shino glazes can be used on this clay without causing significant glaze fit problems. The resulting clay body has a beautiful deep brown color, and a metallic sheen from the reduction firing.
Beach Glass Celadon: This glaze starts as a traditional celadon, but incorporates beach glass as a pigment, rather than the traditional Iron oxide compounds. Being related closely to glaze, glass uses virtually identical pigments to create color. By taking a combination of blue, green and brown glass washed up on the shores of the Detroit river, I can grind these materials into a fine powder, and essentially create a “stain” of my own. Because this material contains cobalt and chrome from these glasses, the colors are more intense, and a bit more reliable and true than a traditional celadon glaze.
Angle Iron Celadon: This is a very traditional celadon glaze. In this case, I have taken sheets of rust from the Angle Iron supports of an old salt Kiln that was torn down and re-built during my first year at Pewabic Pottery. This was my first kiln-building project, and is full of nostalgia for me because of the friendships that we made while working on it. The rust sheets were ground and ball-milled to create a very fine iron oxide that is used to color this glaze.
Molasses: This glaze started as an amber-colored, high-iron ash glaze. I’ve incorporated concrete dust into it as a source of calcium. Processing the concrete so that it is usable requires calcining the material to break down the chemical bonds that hold it together, and then carefully screening out the sand and gravel that is added to the concrete during the original mixing process. It is quite a caustic material, so care needs to be used when handling and spraying the glaze, much like an ash glaze. I have carefully adjusted it so that it is fluid enough to highlight the carved decorations on my pieces, but is still stable enough to keep it from running badly.
Belle Isle Black: This is one of my favorite glazes. It’s a high-magnesium matte black glaze that is based mainly on a red local clay that was sourced from Belle Isle, a state park in middle of the Detroit river. The majority of my glaze materials wash up on the shores of the island.
Brick Powder Slip: This is a simple flashing slip that I use for soda firings, made by blending ground brick powder with Kaolin, and small amount of feldspar. The brick powder deflocculates the slip, making it ideal for bisque application without cracking, and the Iron in the original brick clay gives the slip a beautiful color when flashed by the wood ash and soda in atmospheric firings. Coming from a city with a northern climate, the small chunks of brick that wash up out of the river have been exposed to possibly over 100 years of freeze-thaw, making them extremely porous, and easy to break down into a very fine powder.
Slate Shino: This simple shino glaze contains powdered slate from the roof of Detroit’s old University Club, now demolished. This historic gem was an incredibly beautiful building full of intricate architectural details. Tragically, it fell victim to urban decay, corruption and looting, and had to be torn down several years ago. I was lucky enough to salvage some of the old roof tiles from the grounds just before it was demolished, and used a ball mill to grind them down to a fine powder. The iron in the slate gives the shino it’s rich red-orange color over the porcelain clay that I use.
Luster Shino: This glaze is a layering of a high-alkali Shino over a dark iron-rich slip containing ground brick powder. The high iron concentration combined with the carbon trapping caused by the high soda content of the glaze causes the intense metallic luster in the fired glaze surface. This is one of my favorite, but most unreliable and variable glazes.