Arts and sciences

Behind every art is science.

Of course, you can produce beautiful art without knowing any scientific details; the Renaissance masters created gorgeous paintings without knowing the exact chemical composition of their paints.  It's amazing, really, that they accomplished what they did, combining their astonishing talents and aesthetic senses with materials developed using what amounted to trial-and-error.

I wouldn't consider myself an artist, but I do play around with clay, and I've gotten the chance to geek out over the scientific side of pottery -- specifically, glaze chemistry.  Glazes are generally made of four ingredients -- a glass-former (usually some form of silica), a flux (which lowers the melting temperature of the mix and make it flow), a refractory material (to give it stability and viscosity), and a colorant.  One of the first things I learned when I started making pottery, though, is not to assume the final product after firing to 1200 C will be the same color as the raw glaze; in fact, the reverse is usually true.  Here's a kiln load, coated with various raw glazes, before firing:

And the same kiln load after firing:

The changes that occur during firing always strike me as something very like alchemy.  Even knowing a bit about how they work -- and what I know is, honestly, little more than a bit -- there's still an unpredictability about glazes that make them fun, exciting, and occasionally exasperating to work with.

I was reminded of my trials and tribulations -- and occasional triumphs -- with glaze chemistry as I was reading a paper in Proceedings of the National Academy of Sciences - Nexus a couple of days ago.  Called "Marangoni Spreading on Liquid Substrates in New Media Art," and written by San To Chan and Eliot Fried of the Okinawa Institute of Science and Technology, this paper looks at the creation of intricate and beautiful fractal patterns using little more than acrylic ink and paint, water, and rubbing alcohol.

The technique involves applying tiny droplets of thinned acrylic ink onto a painted surface.  The irregularities in the surface draw the liquid away from the point where it is applied, and the design develops as you watch, creating branching patterns resembling snowflakes, neurons, or lightning.  Just as with ceramic glazes, the exact mix of the various ingredients can drastically change the results.  The process works because acrylic paints and inks are thixotropic, meaning that their viscosity changes when they're stirred or shaken (a common thixotropic substance is ketchup -- which is why you have to shake it or it won't pour).  The water and alcohol change the viscosity, and in combining the ingredients there's a sweet spot where the mixture is viscous enough to hold together into threads on the painted surface but not so viscous that it doesn't move.

"In dendritic painting, the droplets made of ink and alcohol experience various forces," said San To Chan, who co-authored the study.  "One of them is surface tension -- the force that makes rain droplets spherical in shape, and allows leaves to float on the surface of a pond.  In particular, as alcohol evaporates faster than water, it alters the surface tension of the droplet.  Fluid molecules tend to be pulled towards the droplet rim, which has higher surface tension compared to its centre.  This is called the Marangoni effect and is the same phenomenon responsible for the formation of wine tears -- the droplets or streaks of wine that form on the inside of a wine glass after swirling or tilting."

"We also showed that the physics behind this dendritic painting technique is similar to how liquid travels in a porous medium, such as soil," said Eliot Fried, the study's other co-author.  "If you were to look at the mix of acrylic paint under the microscope, you would see a network of microscopic structures made of polymer molecules and pigments.  The ink droplet tends to find its way through this underlying network, traveling through paths of least resistance, that leads to the dendritic pattern."

I love knowing the science behind the arts (although I must admit that the mathematics in the paper about dendritic art lost me pretty quickly).  It was great fun, for example, that the fiddler in the band I was in for ten years was a physics professor at Cornell University and taught a class called The Physics of Music -- she more than once told me things about how my instrument worked that I honestly hadn't known (such as why flutes go sharp when they warm up).  

I don't know about you, but knowing the science of how things work enhances my appreciation for their beauty.  I've loved Bach's music ever since I first heard it as a teenager; but now, understanding how fugues and canons are constructed makes my wonderment over pieces like the astonishing A Musical Offering that much more profound.  Likewise, my knowing a little about glaze chemistry enhances my enjoyment of the beauty of the results.

Science itself is beautiful.  And when you combine it with art and music, you have something truly magical.

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Pottery in motion

Making pottery is a complicated enterprise.

I say this from some degree of personal experience.  About ten years ago, on the urging of my artist wife, I took a class to learn how to throw pottery.  For those of you who have no experience with this particular avocation, I'm not talking about hurling plates against the wall, which, of course, you wouldn't need to take a class for.  "Throwing," in pottery parlance, is the process of using a spinning pottery wheel to shape symmetrical vessels out of clay.  Some people still use old-fashioned "kick wheels" -- where the axle of the wheelhead attaches to a heavy stone disk set in motion with the feet, and the momentum of the disk keeps the wheel spinning (for a while, at least).  Fortunately -- because learning to use a kick wheel takes a whole different level of coordination -- I learned to throw on an electric wheel, the speed of which is controlled by a foot pedal a little like the accelerator of a car.

Which is hard enough.  The first pieces I made looked like they were created by a kindergartner, or perhaps an unusually talented chimp.  I'm not very artistic, and improvement was slow, but I've gradually gotten to the point where I can turn out a decent-looking piece of pottery.

One of my better efforts

My first pottery teacher told us, "Never get attached to a piece until it's cool, in your hands, after the final firing."  It's good advice.  There are a million things that can go wrong.  After the piece is thrown, it still needs to be trimmed (removing excess clay at the bottom and finishing the shaping), have any modifications added (such as the spout and handle on the pitcher in the photograph).  Then it needs to dry -- without cracking.  (Cracks usually happen because the piece dried too fast or else unevenly, often when it has thicker walls at the bottom -- a common amateur mistake.)  Then it has to be "bisque fired," converting the raw clay to ceramic, usually at a temperature of about 1000 C.  Then it's cooled, and (most often) coated with a glaze to make it both attractive and water-tight, and re-fired at a higher temperature (depending on the clay and glaze used, between 1200 and 1400 C).  At every stage, the piece can crack, warp, or sag.  The glaze can malfunction in innumerable ways, including forming blisters or pock marks, pulling away from the clay (crawling), splintering as it cools (shivering), or even adhering to the clay and then shrinking and triggering spiral cracks (dunting).

Or, as happens all too often, you can just take the piece out and think, "why did I glaze it this way?  This looks like crap."

But every once in a while, all the stars align, and you get a piece that's really nice.

My favorite coffee mug

The reason all this comes up is a new study in Nature Human Behavior that looked at two interesting things: first, how far back the tradition of pottery-making goes; and second, once it arose, how quickly it spread.  The earliest pots known come from about 16,000 years ago in China and Japan, but after that it very quickly spread amongst the hunter-gatherer societies, and by 10,000 years ago it was found throughout the Near East and Europe.  (Pottery-making in Africa and the Americas is thought to have had an independent origin, but showed up around the same time.)

The authors write:

Human history has been shaped by global dispersals of technologies, although understanding of what enabled these processes is limited. Here, we explore the behavioural mechanisms that led to the emergence of pottery among hunter-gatherer communities in Europe during the mid-Holocene.  Through radiocarbon dating, we propose this dispersal occurred at a far faster rate than previously thought.  Chemical characterization of organic residues shows that European hunter-gatherer pottery had a function structured around regional culinary practices rather than environmental factors.  Analysis of the forms, decoration and technological choices suggests that knowledge of pottery spread through a process of cultural transmission.  We demonstrate a correlation between the physical properties of pots and how they were used, reflecting social traditions inherited by successive generations of hunter-gatherers.  Taken together the evidence supports kinship-driven, super-regional communication networks that existed long before other major innovations such as agriculture, writing, urbanism or metallurgy.

What blows me away about all this is that -- as I said earlier -- pottery-making ain't easy, and that goes double if you don't have modern technology to help.  First, you have to find a source of usable clay, which is by itself not simple.  Clays, depending on their chemical composition, fuse and turn into ceramic at different temperatures; an iron-rich earthenware, such as the clays used by the amazing potter Lucy Martinez, of the San Ildefonso Pueblo community, fire to a much lower temperature than kaolin-rich fine-grained clay of the type used in the classic Jingdezhen porcelains.  Fire a piece made from earthenware clay to the temperature used for porcelain, and it will simply melt into a puddle all over your kiln shelf.

Then there's learning which materials to use as glazes.  Our ancestors didn't have the refined glazes in plastic bottles that I use; they had to learn which naturally-occurring minerals would melt and coat the surface.  Not only did they have to concern themselves with coverage and water-tightness, they had to learn -- the hard way -- about safety.  Many of the prettiest glazes contain such dangerous heavy metals as cobalt, barium, and lead, and using vessels with those glazes for cooking or serving food could be downright dangerous.  (Now, chemists have done extensive testing on glazes to determine whether they're "food safe;" lead and barium have been almost entirely eliminated, and cobalt formulated so it stays put in the glazed surface and doesn't leach into your bowl of soup.  Fortunately for potters, because cobalt is an essential ingredient for just about all beautiful blue glazes.)

So what's amazing is that our ancestors learned all this by trial-and-error.  No wonder that after that -- as the researchers found -- the technology spread like wildfire.  Everyone would want to learn something that useful.

It's cool that in these days of mass production there are still people who want to learn this ancient skill.  Maybe today, with our electric wheels and factory-processed clays and bottled, tested glazes, we've got it easy compared to our forebears, but we are still using the same skills of shaping and refining and decorating that were developed ten thousand years ago.  When I get on the wheel to make a serving bowl or a coffee mug or a pitcher, I'm working in a medium that links me, in an unbroken line, back to nomadic hunter-gatherers who discovered that with little more than natural materials, a hot enough fire, and a pair of strong hands, you could make something that would last for millennia.

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Feats of clay

As I write this, I'm waiting for a kiln full of pottery to cool enough that I can open it.

Opening a kiln, especially after the final (glaze) firing, is a bit like Forrest Gump's box of chocolates; you never know what you're gonna get.  Even though I have about ten years of experience making pottery, it's still a crapshoot every single time, mostly because so many things can go wrong along the way.  My first pottery teacher said never to get attached to a pot until it's cool, in your hands, after the final firing, and there's a lot of truth in that.  Besides the built-in uncertainty of a complex, multi-step process that never quite works the same way twice, there's the added complication that I love to mess around with new techniques, especially new glaze combinations.

So I must admit that just about all of my failures have been my own damn fault.

Sometimes, though, things work out a great deal better than you expect.

I got into pottery on a whim.  I've never been much good at artistic pursuits -- my former students will attest to the fact that my ability to draw kind of topped out in third grade -- but my wife is a brilliant artist, and had been taking lessons in pottery for a while.  She convinced me to give it a try, and after one lesson I was hooked.  I'm still at it ten years later, even though mostly I still just think of it as playing in the mud for adults.

Then there are the (many) times it doesn't go so well.  We have turned our failures into a game called "Confusing Future Archaeologists."

I've done a lot of wheel-throwing and hand-building, and we now have a studio that is completely taken over by pottery equipment.  I must say, in all seriousness, that pottery kind of saved my sanity during the pandemic lockdown.  Having something creative to focus on was a godsend.

Working on the wheel

I have no desire to learn to be a professional potter; an amateur I am, and an amateur I shall remain.  If every once in a while I produce something I judge as worthy of keeping, that's cool, but mostly I'm just in it to have fun.

Then, there's the potential for combining pottery with my other obsessions.  Yes, I know I'm a total fanboy.  No, I don't care.

The reason this comes up is a paper I ran into a couple of days ago in The Journal of Anthropological Archaeology about the techniques for pottery-making used by the mysterious Indus Valley Civilization of northwestern India four thousand years ago.  A team led by Alessandro Ceccarelli of the University of Cambridge did a detailed analysis of fragments of pottery from the Indus Civilization, and found that they were already using a great many of the techniques potters still use today -- pinching, slab-building, coiling, and wheel-throwing.  You might wonder how the researchers could discern the latter; a well-made coiled pot and a wheel-thrown pot can look a great deal alike.  But microscopic analysis of the shards showed that even after smoothing and firing, hand-built pottery still shows traces of the scraping potters do to join the pieces together and avoid cracking, while wheel-thrown pottery retains evidence of rotational stress in the clay particles that comes from the torque on the clay from the spinning wheel and the drag exerted by the potter's hands.

When I read that last bit, I thought, "Oh, of course."  One of the things wheel-throwers learn very early on is that throwing creates a twist in the clay, even if the homogeneity of the material makes it hard to see.  Multi-part pieces like teapots are where this is the most critical; when you put the spout on a teapot, you have to account for the fact that during firing the clay will "relax" or untwist a little, so what was joined to the body of the teapot as a perfectly-aligned spout can come out of the kiln tilted to the side.  Once you figure out how much the clay you're using untwists, you compensate by putting the spout on tilted a little in the other direction -- so during the firing, the spout will right itself and come out properly aligned.

It's kind of amazing to me how far back these techniques go.  Think about the insight our distant ancestors must have had to take this common substance -- clay -- and fashion it into something not only useful, but beautiful.  Now, I sit down at an electric wheel with homogeneous store-bought clay and perfectly-formulated stains and glazes, and fire my work in an electric kiln.  (And I still have pieces that flop sometimes.)  Consider the trial-and-error that must have gone into digging and refining natural clay, developing techniques for shaping (including figuring out how to build a kick-wheel), figuring out which available minerals would work as colorants and glazes, and using pit firing to harden the clay to make the piece usable for containing food or drink.  Modern potters are the inheritors of what clay artisans have learned over millennia of attempts, innovations, successes and failures.

"This study doesn’t just look at how pottery was made – it gives us a fascinating insight into some of the earliest ‘social networks’ and how people passed on knowledge and skills over centuries without the use of books or the technology we now take for granted," Ceccarelli said, in an interview with Heritage Daily.  "The objects we examined suggested that while communities of ceramic makers lived in the same regions – and often in the same settlements – different traditions emerged and were sustained over centuries.  There was a clear effort to keep alive their unique ways of making pottery to set them apart from other communities, like a statement of their identity."

All of which makes me wonder what those future archaeologists will think about my pile of smashed pottery.

But now, I need to wrap this up, and go check the kiln.  I swear, waiting for it to cool is like a kid waiting for Christmas.  And hoping that the brightly-colored boxes under the tree contain something better than socks, underwear, or an ugly sweater.

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My master's degree is in historical linguistics, with a focus on Scandinavia and Great Britain (and the interactions between them) -- so it was with great interest that I read Cat Jarman's book River Kings: A New History of Vikings from Scandinavia to the Silk Road.

Jarman, who is an archaeologist working for the University of Bristol and the Scandinavian Museum of Cultural History of the University of Oslo, is one of the world's experts on the Viking Age.  She does a great job of de-mythologizing these wide-traveling raiders, explorers, and merchants, taking them out of the caricature depictions of guys with blond braids and horned helmets into the reality of a complex, dynamic culture that impacted lands and people from Labrador to China.

River Kings is a brilliantly-written analysis of an often-misunderstood group -- beginning with the fact that "Viking" isn't an ethnic designation, but an occupation -- and tracing artifacts they left behind traveling between their homeland in Sweden, Norway, and Denmark to Iceland, the Hebrides, Normandy, the Silk Road, and Russia.  (In fact, the Rus -- the people who founded, and gave their name to, Russia -- were Scandinavian explorers who settled in what is now the Ukraine and western Russia, intermarrying with the Slavic population there and eventually forming a unique melded culture.)

If you are interested in the Vikings or in European history in general, you should put Jarman's book in your to-read list.  It goes a long way toward replacing the legendary status of these fierce, sea-going people with a historically-accurate reality that is just as fascinating.

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