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PROSPECTORS: A Conversation with Alex Thullen & Matt Fiske

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.

Alex Thullen at work in his studio

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.


Carved bowl in progress by Alex Thullen.


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.

Large carved platter in progress.

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.



Soda fired vase with Brick Powder Slip by Alex Thullen


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.




CG:What was your first experience with clay, and what was it that “grabbed” you?
Fiske: Like a lot of kids, I grew up playing in the dirt. I remember being about 10 years old and finding a huge mud puddle with a foot of clay in the bottom of it. It was interesting that I didn’t have to think about what to do with it, and I didn’t need any instruction. I just grabbed the clay and started making stuff. Years later, I see this same intuitive response to clay in kids clay classes. It’s pretty amazing to watch them get to work. My favorite approach is to give them a pile of clay and free reign to get lost in their ideas and their projects. I find clay to be absolutely fascinating stuff, and even more so as I learn more and more about it.  From the beginning I think what grabbed me, and what still does, is that it’s a material that responds so well to touch and intention. Working with clay is both frustrating and rewarding, but for me at least, there’s always been an assumption that with practice and discipline you can always become more and more proficient at making.
  I have to give credit to Paula Wells, who was my High School Art Teacher. She was the one that really reached me, in no small part because she gave me free reign of the studio to pursue whatever kinds of projects I was interested in. I remember touching clay as a Freshman or Sophomore in a fundamentals class, but it wasn’t until the end of my Junior year that I saw the potential of the potter’s wheel. It was the end of the year and she invited Tim Wells, a local potter and professor, to come give throwing demos and lead the charge in some Raku firings. He showed me how to throw a cereal bowl kind of form, and that was really it. From that moment on I had the basics of it down, and I knew the moves, but it was impossibly difficult to make the forms that I had in my head.  During my Senior year I spent as much time as possible on the potters wheel.
    As I became more proficient at making, Paula explained what glazes were and how I could develop my own. She explained the whole thing by way of analogy to baking recipes and cookies. For whatever reason, the idea that I could concoct my own unique recipes really appealed to me. I started experimenting without really having any clue what the materials I was mixing were, but I really enjoyed being the one in the class with glaze surfaces and colors that stood apart from everyone else’s. There was also the anticipation of putting a bunch of potential glazes into the kiln and waiting to see what happened. That grabbed me just as hard as the challenge of the potter’s wheel. To Paula’s credit, she saw some potential in me and spent a lot of time explaining how to do a triaxial blend as well as bringing me books to look at. Beyond the technical and practical stuff she taught me, she really gave me a place to explore the possibilities of ceramics on my own terms.
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?
Matt Fiske prospecting glaze materials in Eureka, Utah

Fiske: It’s no coincidence that all of my best prospecting spots are in close proximity to good fishing, hiking, or camping spots. I will occasionally set out to go digging for a specific material and a mission to go collect it – but usually my discoveries come about from rambling around backroads, or driving into the mountains with my eye out for color and texture. More than anything, the main objective is to get the hell out of the studio and go exploring. This approach has evolved quite a bit over the years, and wasn’t really a thing until my time in Graduate School in Utah. For those who haven’t been, Utah is a kind of geology and ceramic material paradise. At the time it was hard to justify driving out into the desert or up into the hills just for camping and hiking, or just for research and studio work. These days, it’s critical for me to step away from the studio and get outside and recharge.

There’s a picture I like to use in my slide talks, and it was taken by my mom when I was three or four years old. In it, I’m sitting in one of her flower pots in a pair of overalls with a hammer and shovel. I like to joke that this was where I got my start in “digging”. It’s true that throughout my childhood I had a rock collection and I usually had my head to the ground looking for interesting rocks and fossils, but it’s probably a bit more accurate to say that I didn’t really get my start in prospecting until early on in my career, right around the time I became a BFA in Ceramics at Indiana University Bloomington around 2005. At the time I had a friend who was an avid rockhound and a mineral collector. He would do rock and gem shows, and he had an absolutely massive collection. He was also somewhat of a cowboy when it came to going out and digging up fossils and geodes all around Indiana. More than being jealous of his collection, I was really jealous of his mental catalogue of materials and
Local Red Lodge Kaolin from a vein in the Stillwater mountains.

locations. I learned a lot hanging out with him and few other rockhounds – and pretty much everything I’ve learned since then was the result of going out and doing it. As far as I’m concerned, you can’t really learn rockhounding or prospecting from a book (although Falcon Guides have a really good series of books on Rockhounding – I have 5-6 of them from all the different states Ive lived in!). I think the best way to go about it is to just get out there and start picking up stuff. The real trick is to then put it straight into a kiln. Early on I often made the mistake of collecting a bunch of material and then never getting around to using it. Getting results immediately is super important. It seems that the longer you wait to test something, the likelihood of never using it increases dramatically.

The connection between prospecting and glazes happened pretty slowly for me, and my approach and studio practice is still evolving as I learn more. From pretty much the beginning of my ceramic career, though, I was really interested in glaze formulation and glaze chemistry. When I was a BFA I was fascinated with learning what all the commercially available materials were, and what the different ‘flavors’ of those materials were. One project that taught me a lot was testing about 30 different clays in a basic celadon glaze recipe. It was pretty astonishing to see the differences in color that occurred just by substituting another clay for EPK. Gradually I started to learn more about the materials in the glaze lab, and how they functioned in glazes.  Slowly but surely I started taking more risks and substituting more and more glazes. By the time I got to graduate school, I’d had a lot of experience developing, mixing, testing, and most importantly, firing glazes. I went to Utah State because that school has a reputation for being a great place to do technical research. It was the right place at the right time, and I was offered an ART-STEM scholarship, which was basically science funding set aside for an Art graduate student. That scholarship really opened a lot of doors into the geology department, and besides taking Mineralogy and Volcanology classes, I spent a lot of time talking and working on projects with the students and professors. It was really during my three years of graduate school that my whole approach and practice of prospecting for ceramics picked up momentum and got quite a bit more sophisticated. While it’s true that I have learned a lot about rocks, and minerals, and geology – the fundamentals of going out and exploring, satisfying my curiosity, troubleshooting, testing, and systematically developing new ceramic glazes have stayed pretty much at the center of my studio practice.



Clay Body: For the past few years I’ve used Laguna 550 Porcelain. Although it’s on the pricier end of the spectrum, I’ve had really great results in a wide range of firing atmospheres and temperatures. It looks good in cone 6 electric, it holds up in cone 12 oilspot firings, it’s a beautiful translucent bright white in reduction, and it’s not too yellow or grey in oxidation. In addition to it’s fired characteristics; it also throws really well and is reasonably resistant to warping and cracking. My best guess is that it’s a Grolleg Kaolin based recipe with soda feldspar, silica, and white bentonite. It looks almost identical to the porcelain recipe I use when I have access to a good mixer and a pugmill: 55 Grolleg, 30 Minspar, 15 Silica, 2 Macaloid.

  The decision to use a single, commercial clay body came after the realization that my real interest was in glazes. With so many variables in the glaze materials and firing processes I’m interested in testing, the very last thing I needed was another variable to account for. There’s also the issue of scale. When prospecting glazes, I like that the scale of collection and storage is in the 10-20lb, 5 gallon bucket range. When it comes to prospecting for clay bodies, the scale is more like 1000-2000lb, pickup truck range. I wish that I had the time and energy to make wild clay bodies – but the truth is that I’m just way more interested in spending my studio time throwing, glazing, and firing.


Glazes: For the past year and a half I’ve been really interested in Soda Firing, and I’ve been exploring 3 glazes. To these glazes I’ve been adding a copper material that I prospected outside of an old copper mine in Millford, Utah. I’ve been calling it Copper Sand, because it looks a lot like a bright green sandy dirt. Rather than ball milling, I’ve been experimenting with adding very coarse material into my glazes, and brushing them on. When I go to glaze I have about 5 ziplock bags of material sorted by particle size (6-12 mesh, 12-24 mesh, 24-40 mesh, 40-60 mesh, 80+ mesh), my buckets of glaze, and 3 small bowls of glaze to mix in the material. In the first bowl I usually have very coarse material, in the second bowl is finer, and in the third bowl is a mixture of the two. After lining all of my pots and allowing them to dry, I brush on the glazes, paying attention to glaze thickness and the amount of material going onto the pots. As I go along, I’m constantly adding more glaze and copper material to the bowls.


Copper Sand:  From a commercial standpoint, this material is a mid-grade copper ore. Because it was collected from the tailings pile next a mine, there’s really no telling when and where it was dug up. That said, I’ve learned a lot about it through trial an error. To make a very long and complicated geologic story short, it was at one point, a limestone rock. This limestone rock moved over a volcanic hot spot in the earth’s mantle, and was subsequently covered in a very thick, very erosion resistant volcanic layer of rock. Millions of years later, the tectonic plate switched directions and moved back over the hot spot. As a result, the limestone layers underneath the cap of volcanic rock were steamed and stewed with a mixture of sulphides and metal-rich solutions. For the past few million years, the volcanic cap has slowly weathered away, and the underlying copper/silver/gold/lead/tin/tungsten rich rocks and minerals have been exposed to enterprising miners. My best guess is that the particular material I collected was unearthed in the 1960’s or 1970’s and has since been slowly decomposing and breaking down in the Utah desert. It’s an extremely variable combination of mostly calcium carbonate, pyrite, arsenopyrite, and hematite – but it’s also contains varying amounts of tin, zinc, molybdenum, tungsten, titanium, gold, silver, lead, cobalt, magnesium.


Turqouise/Oribe Glaze: This is a glaze commonly found in a lot of studios, and is characterized by additions of copper carbonate to make for a watery blue/green. In oxidation it can make for a bright Mediterranean blue, and in reduction is can form a metallic microcrystalline black/green surface. With the addition of the varying coarseness of my copper sand material, I sometimes see streaky, webby, ash-glaze-like blue fields with silver crystals. I usually see a lot of greens and turquoise with black spots and speckles. I also occasionally see bright pink and red lichen-like surfaces. It’s a really variable glaze, and a recipe called Turqouise, which is very similar to mine, can be found in John Britt’s High Fire Glaze Book. My variation has a range of about cone 8-cone 10, and much hotter than that, it runs like crazy.


Hayne’s White: A very standard white liner glaze. My own variation uses Minspar, +10% superpax, and EPK. In the soda kiln, it has a tendency to carbon trap very nicely as well as crystallizing in very interesting ways. It’s much more resistant to running as my other two glazes, although it is very susceptible to blushing pink and purple when it’s next to copper glazes in the kiln. This glaze has a range of cone 9-11.


Celadon Blue: Another classic studio glaze, my recipe uses prospected basalt for the colorant. It’s also on the low calcium, high sodium spectrum of Celadon glazes. (It’s basically a celadon/copper red hybrid) As such, it doesn’t go matte in soda firings, but remains bright and glossy. It also has a tendency to carbon trap and blush when it’s next to copper glazes in the kiln. With additions of fine copper sand, it develops a rich copper red, and with coarse additions, it forms black and bright blue spots and speckles. Because this glaze tends to flux early on, it has a really wide range in the soda kiln and looks good between cone 6-10, and like the oribe, it runs like crazy beyond cone 10.

3 variations of Fiske’s explorations into the use of prospected copper sand.




Click HERE to view available works from the show.

We are beyond thrilled to host this exhibition at Companion Gallery.

If you have any questions feel free to call the gallery

at  (731) 267-7784 between 11am and 9pm.