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.

****************************************

Clay magnets

One of the most wonderful things about science is the role creativity has in discovery.  Problems that have been considered somewhere between difficult and intractable have often been solved by someone who has a sudden creative insight -- how to bring together two previously disparate bodies of knowledge, or using a technique from one realm to study an entirely different one.

Take, for example, the study that was sent my way by a reader of Skeptophilia a couple of days ago.  It has to do with the technique of paleomagnetism -- the "geological clock" provided by the fact that the Earth's magnetic field flips, for (thus far) reasons unknown.  You're probably familiar with the most famous use of paleomagnetism; it was the technique that finally cinched down the plate tectonic model as accounting for continental drift.  When magma solidifies into solid rock, tiny ferromagnetic particles that were once free to move become locked into place.  When the rock was liquid, those particles could swivel around and line up with the magnetic field of the Earth at the time; once solid, that magnetic signature was frozen in place.  When geologists doing magnetometer readings of the ocean floor on either side of the Mid-Atlantic Rift Zone found parallel stripes of rocks with the same magnetic signature, and the rock as they neared the ridge had progressively younger radioisotope ages, they knew that there was only one explanation.  New rock was welling up at the ridge from deep in the mantle, and that was pushing the plates apart, creating strips of new ocean floor all along the ridge.

[Image is in the Public Domain courtesy of the USGS]

Now, a new study has applied paleomagnetic techniques to a completely different problem.  A team at Tel Aviv University and the Hebrew University of Jerusalem has looked at the magnetic signature left in fired clay bricks -- and used it to date archaeological strata in order to pinpoint the dates of famous battles described in the Biblical Books of Kings.

Clay retains a fossilized magnetic imprint for the same reason that magma does; when the clay is plastic, the particles are free to move, but once it's fired, they're stuck in place.  What's coolest about this study, though, is how sensitive the technique has become.  Back in the 1950s, when Fred Vine and Drummond Matthews used paleomagnetism to study the sea floor, it was pretty crude.  The best they could do was say that a particular sample of rock had a magnetic field like the one we have today (shown in white on the above image) or one that was reversed with comparison to the current orientation (shown in various shades of orange).  This wouldn't be much help in archaeological settings, as the last complete polar reversal was 780,000 years ago.  Now, the technique has improved to the point that the scientists can detect tiny fluctuations not only in direction but in strength -- and that has allowed them to date strata with an accuracy of ten to fifteen years.

This has allowed the team to pinpoint firm dates of offensives against the Kingdom of Judah by Shoshenq I of Egypt (1 Kings 14: 25-26), Hazael of Damascus (2 Kings 12:18), Tiglath-Pileser III (2 Kings 15:29) and Sennacherib (2 Kings 18-19) of Assyria, and Nebuchadnezzar II of Babylon (2 Kings 25:1-21).  And while some of the findings confirmed previous dates for sites, the more accurate technique has disproven other conjectures.  For example, the site of Tel Beit She'an, thought to have been razed by Hazael of Damascus, showed a paleomagnetic date between seventy and a hundred years earlier, meaning it had fallen not to Hazael but to the campaign of Shoshenq of Egypt.

It's not only the fineness of the technique I find impressive, but the fact that the team thought of using it at all.  Creativity hinges on divergent thinking -- the ability to see multiple solutions to a problem, and to apply out-of-the-box techniques in order to find those solutions.  This is an excellent example of just that -- using a technique first pioneered in studies of plate tectonics to establish a timeline of biblical archaeology more accurate than anything we've had.

Makes you wonder what crossovers scientists will come up with next.

****************************************

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.

**********************************

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.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Cures for vaccination

It's with a strange twinge of conscience that I'm writing today about an alt-med woo-woo claim that I don't think we should challenge.

It popped up on the website BabyCenter Community a couple of weeks ago, but apparently has been gaining ground since then, showing up on Facebook, Twitter, and websites devoted to anti-vaxx and holistic medicine.

The claim: putting a clay plaster on a vaccination after you get back from the doctor's office will "draw out the vaccine."

The first place I saw this -- the website linked above -- posed it as a question, where it received the following answers:

It helps to pull some of the toxins back out.  Not all though.

 

apparently it is possible to remove all vaccines, infiremiere [sic] should be a day in their vaccines in order to work in a hospital, she made all her vaccination and immediately after the injection, she had everything prepare in advance, she it [sic] absorb the vaccine in his car

with a homeopath here in France It can remove inject vaccine long ago, as soon as I have more information I will send you

One person did say that it wouldn't work, that vaccines are irreversible; but another, much more authoritative respondent came back with the following:

Hello,

For mandatory vaccines that nobody escapes, there is indeed the clay poultice can reabsorb the "poison" from his injection. The method is as follows:

You buy a clay tube (health food stores) and you present to vaccination equipped with this tube, gauze and tape. Once the vaccine was injected, you go to the toilet and you put a thick layer of clay on the vaccine + gauze + tape. Keep this poultice for 2 hours and the vaccine will be almost completely absorbed by the clay.

Upon returning home, you take the natural vitamin C (Acerola C, for example) or magnesium chloride (pharmacy: A bag of 20 grams dissolved in one liter of water and take 1 glass morning, afternoon and evening up. 'to exhaustion of a liter).

So I was reading this, and I was thinking... maybe it's better we let them think this is true.

After all, then the kids will be vaccinated and protected from disease, decreasing the likelihood of outbreaks of preventable diseases; and the adults will conclude that they've won, that they fooled us silly ol' skeptics and scientists, and in consequence, they'll shut up about it and stop trying to fight mandatory vaccination laws.

So, maybe there is a time that it's better to let the woo-woos continue in their beliefs, especially when one particular woo-woo belief cancels out the ill effects of another one.

But I do say this with some degree of guilty feelings.  Because, after all, the whole approach of a skeptic should be to follow wherever the evidence leads, to try to promote clear thinking and the scientific approach for one and all, and in any situation where the scientific approach applies.

Here, though... maybe we should let them have their clay poultices and acerola detox cleanses and homeopathic anti-vaccine remedies.  Let 'em think they've beaten the system.

And hope like hell that their children grow up to understand science better than the parents did.