Wednesday, September 2, 2015

Science of art, art in science: a potter's perspective


-Alison

While I love volcanoes and doing science, I do try to spend some time doing other things. In fact, I am frequently reminded that the best thing a person can do for their own success at work is to have something else in their life that is NOT work, but still feels valuable to them. For any graduate students I would actually stress that this includes you.
My activity that I do just for me is pottery. Which as a geologist isn't as separated from science as some might think. Science and art are not incompatible. Frankly I find them to be good friends. Where would we be if the early naturalists didn’t spend hours making amazing sketches of landscapes and animals? There would be several species that we know nothing about, or historical volcanic eruptions that changed the face of a mountain, but which part? If you are interested in science inspired art then Twitter has a hashtag for you #sciart. And if you are just into beautiful images of things from nature I would suggest #thinsectionthursday. A thin section is a 3 mm thick slice of rock that we shine light through to look at minerals and glass in detail. It is good to see the art even in our laboratory samples.  These are my personal favorites, but there are many more.
Thin sections are beautiful. This one even has a duck. This clinopyroxene is viewed through cross-polarized light surrounded by volcanic glass (black).
Pottery is made from earth materials, the clay body itself and the glaze, are made of mineral components. Pottery is a place for me to make a mess, build something, destroy it, and then rebuild it. I can experiment without focusing on precision, and I can incorporate elements of my love of geology into that work.
Making a mess while adding a foot to the bottom of a bowl.
Most clay bodies have a combination of clay minerals: kaolin, smectites, etc. The clays are phylosillicates which means that they form small crystalline sheets, where the key component is silica. The crystalline structure can absorb water readily between these sheets. There are hundreds of clay minerals that form from the breakdown of other minerals and can have lots of different cations: calcium, aluminum, potassium, magnesium, iron etc. When wet, clays are malleable, and that is what makes the whole process of pottery possible.

Vermiculite is a good example of sheet silicates (phylosillicates). You can see how the big chunks are made up of smaller sheets. Water can be stored between those sheets at a molecular level, that's what makes pottery possible. (Wikimedia commons).
Clay bodies can also contain other materials to help provide strength or reduce shrinkage that happens when you dry the clay out. Grog is a common additive to clay that is frequently made out of lithified clay, or clay that has already be heated in a kiln to a point where the individual grains have been cemented together.  Porcelain is on one end of the clay spectrum having no grog, and when you want to throw it is extra slippery, but does make very thin delicate pieces. Stoneware is a group of clays that contain various amounts of grog. Usually the more massive a piece you want to make, the more grog you want.

Glaze is a chemist’s playground. There is far more room for experimentation in glaze composition with results from the drab to the exciting. Glaze serves multiple purposes from decoration to making a surface watertight and food safe. The glaze most people are familiar with contains high amounts of silica, just like lava, which form a glassy or vitreous surface after being fired in a kiln. The components added to glaze not only make the colors change, but also control the temperature that the mixture melts. The addition of fluxes to a glaze, much like the combination of elements in magma, control what temperature it is liquid and what temperature it is a solid. As the geologists would expect, common fluxes include sodium, potassium and calcium. Elements that are there for color include iron, copper, cobalt and zinc. Cobalt and copper are usually attached to carbonates to help make them stable in the final glaze. Glazes used to contain lead, but like paint, we have learned how to make a full color palate without putting mobile toxic elements next to our food. You can still find decorative only glazes that contain elements you wouldn’t want to eat, but your neighborhood clay artist won’t be sneaking anything suspicious into the piece you liked at that craft fair. The final component is usually aluminum as it helps the glaze behave, or not run off the size of the pot when being fired.
Other color effects come from interactions between the clay body and the glaze, from being in an oxidizing or reducing environment, or salt added to the kiln. One of my favorite color techniques is to apply iron oxide directly to a piece then fire at high temperature in an oxidizing environment and it produces a nice rust color. Not good for eating, but it does help texture pop.
A bear modeling the iron oxide wash.
The temperatures that pottery is fired range from lower than magmatic temperatures to close to the basaltic liquidus at the Earth’s surface (600-1400 C, or 1300-2600 F). The liquidus is the temperature where a melt is completely liquid, no crystals or glass left. Basaltic lava usually erupts at 1100-1200 C on the surface of the Earth but by the time it is at the surface there are usually a few crystals starting to form. Rhyolite lavas erupt closer to 800-900 C. When a piece of pottery is made the first step is to form the clay and dry it. This piece, called greenware, is then fired at temperatures between 950-1000 C (1750-2100 F). This piece is now called bisqueware. It’s fairly stable, but not yet waterproof or ready for the hard usage of a dinner plate. Glaze gets applied as a paste, brushed, dipped, or sprayed on. Once this dries it gets fired again. The temperature that the glazed piece is fired ranges a lot more depending on the composition of the glaze and desired effect 999-1300 C (1830-2381 F). The silica needs to partially melt, but not run off the piece. When it cools it forms the glossy surface we want for a functional surface.

 
Glazing can be a stressful procedure with lots of opportunity for disappointment. However, when a glaze works just right it is super rewarding. Every potter finds their own happy approach to these steps. It takes a lot of time, occasional experimentation, failure, and adaptation. My current favorite approach to finishing pieces is to add some volcanic ash to my work. When I have access to high temperature equipment I mix the ash (typically very fine basaltic ash, well sorted) into a glaze. The result is small flecks of color from the iron and glass melting partially in the glaze.
The specks within the glaze are from basaltic ash from Askja Volcano in Iceland.
More recently I have been working at a studio at lower temperatures. So I have been taking ash, and in some cases small lapilli, and mixing them with a slurry of very wet clay to make what is called a slip. This slip gets applied to the still-wet pottery. The rest of the process follows in the same pattern described above. The final piece has a textural element and depending on the glaze some color from the ash. I also have been known to depict volcanoes on the pots.
Ash texture under white glaze. Ash from Sakurajima Japan.
 
Volcanic ash slip from Lunar Crater Volcanic Field under a yellow glaze.

Coarse ash from Sakurajima Volcano Japan under various green glazes.
I also will be more literal with some of my volcano and geology art. As most of these are gifts they tend to have a meaning to the recipient, whether they just love geology, or they want to see a certain location in 2-D on a piece they can use everyday. I've recently started making pieces for finishing graduate students. They provide me with ash or powdered rock from their field area and I turn it into a piece of pottery.
The Galapagos islands.
 
Lenticular clouds over Kamchatka Volcanoes.

 
Does your spoon holder have volcanoes on it? The volcanoes depicted are from Kamchatka and the ash is from Iceland.
 
I also have been known to depict other geologic relationships. You could use this as a block diagram to test student's knowledge of the basic principles of geology. Can you find the cross cutting relationships and name the type of fault?


I have also embraced larger pieces of volcanic rock, and just glued them on afterwards as an accent.
This lid handle is much better with a piece of scoria on it. You can note a map of faults and fractures in the background if you needed more proof that I am a geologist.

One of the most rewarding parts of making pottery is when you get to see your work incorporated into people's lives. They get to interact with your art, and they might even break it. But it provides good perspective. It is always good to make time for life outside of work, and art is one good way that I add balance to my life. 

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