Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond. Visit our website at www.thedeepradioshow.com
Today we’re going to go on a world-spanning journey that also digs into our own past here in the Marianas. We’re going learn about a remarkable pigment called Maya Blue
PAINTING THE SKY (AND OTHER THINGS)
If you have any interest in ancient times at all, you’ve heard over and over again that all those beautiful white Greek and Roman statues weren’t white when the Greeks and Romans were enjoying them; but painted in life-like colors. As a matter of fact, just about any ancient stonework was originally painted in bright vibrant colors, from temple walls to ancient ceramic vessels.
Most ancient dyes are very unstable and although traces of them have been detected which allows researchers to say the items were originally painted, the items themselves tend to be a uniform white (or the color of the underlying stone or ceramic).
The wall frescoes of ancient Egypt retained their colors for the most part for two reasons. It’s very dry in Egypt and the frescos and other grave goods had been in the dark for two or three thousand years. Humidity and light are the two main enemies of all dyes.
Which makes it all the more astounding when archeologists began to excavate the ancient Mayan civilization in hot, humid Mexico and discovered the same monotonous whiteness, with an astounding exception. If the Mayans had painted something sky blue; it still was!
Although you may not be able to tell from this picture; most of this Mayan head is the standard bleached white, but the earrings are still blue.
The composition of this remarkable dye remained a mystery until the 1950’s when diffraction techniques revealed that the dye was made from a certain type of rare clay and the blue dye indigo.
Indigo is derived from the shrub Indigofera tinctoria, which is native to Asia. Although you may not have heard of the dye or the plant it’s derived from, you’re certainly familiar with the color because indigo is the primary dye in blue jeans. And you could probably guess that indigo is not a particularly stable dye because those jeans most of you are wearing are not the same color they were when you bought them (unless they were prefaded!). You also eat a lot of indigo. If you’re eating something blue or purple, check for “FD&C Blue No. 2” on the label and you know you’re eating indigo.
Although it’s not common knowledge, indigo has a local connection too. The Spanish were determined to make the Marianas into a paying proposition and in addition to the copra plantations, and the capers they planted and forced the Chamorus to gather and process, they also planted Indigofera all over northern Guam. And it’s still there today.
I teach a course for teachers called “Hands-On Science” and one of my activities involves making dyes from local plants and materials. I was extremely happy when I discovered that indigo grows wild here since it’s such a major dye source.
Many plants that contain natural dyes leave colored streaks when rubbed on coarse paper but when we tried it with all parts of the indigo plant, absolutely nothing happened. No blue color of any kind. Needless to say, the teachers and I were very disappointed.
Then I learned that indigo is a very challenging dye to use because it isn’t water soluble. You have to use harsh reducing chemicals and even when you remove it from the dye bath the indigo quickly combines with oxygen in the air and reverts to its insoluble form. When it first became widely available in Europe in the sixteenth century, European dyers and printers struggled with indigo because of this distinctive property. Indigo processing requires many toxic chemicals, and just like the mercury used in felting that produced the Mad Hatter, many indigo workers suffered and died for their trade. (See the next section.)
In the 50’s, scientists discovered that Maya Blue was made from indigo and a type of clay called “palygorskite”. Palygorskite has connections to the Mad Hatter too because palygorskite is a type of clay used in Fuller’s earth. Fuller’s earth is used to decolorize, filter, and purify animal, mineral, and vegetable oils and greases. Removal of the sheep fat from the material used to make hats keep them from smelling bad in the rain!
Although I don’t think there’s any palygorskite in the Marianas, you’ve probably eaten a little of it too. Palygorskite binds to acids and toxic substances in the stomach and digestive tract and is used in several anti-diarrheal medications. The Mayas used it for this purpose over a thousand years ago.
When you heat indigo and palygorskite together, it produces Maya Blue. In 1993 a Mexican chemist reproduced the formula for Maya Blue. It turns out that the compound is remarkably stable (as one would assume since time does not fade it) and there is ongoing research on this and other dyes and pigments to create more permanent colors.
There is also ongoing research on the location of the components of Maya Blue. Recently, Spanish researchers traced the route followed by the Maya to obtain palygorskite clay. The Indian communities of Mexico still use palygorskite clay for a variety of purposes, ranging from making candles on All Saints’ Day and household and artistic pottery to remedies for mumps, stomach and pregnancy pains and dysentery. And like the ancient Maya they still use palygorskite to produce anti-diarrhea medicine.
The researchers found samples of high-purity palygorskite clay in several locations on the Yucatan Peninsula, in a 30-mile radius of the well-known Maya archaeological site of Uxmal. Some of these locations are well documented, but others were discovered for the first time during the expedition.
The researchers then did chemical analysis to confirm that, like most clays, palygorskite is made mostly of silicon and oxygen with significant dollops of aluminum and magnesium. The results will allow archeologists to determine whether the clay used for Maya Blue was taken from Uxmal or the surrounding area.
Of course, being the scientist I am, all this has left me wondering what happens if you take medicine for your diarrhea and eat blue M&M’s at the same time. Is your digestive tract permanently stained blue?
Somehow I doubt it; (probably not enough heat in there!) but our quest for Maya Blue has certainly taken us down some strange pathways, from the ancient Maya to the Mad Hatters of the 1800’s to our very own back yard.
Tea with the Mad Hatter
Have you ever had one of those conversations with someone where you seemed to be talking at cross-purposes? Have a look at this excerpt from Alice in Wonderland and you’ll see what I mean.
Alice had been looking over his [the Mad Hatter] shoulder with some curiosity. `What a funny watch!’ she remarked. `It tells the day of the month, and doesn’t tell what o’clock it is!’
`Why should it?’ muttered the Hatter. `Does your watch tell you what year it is?’
`Of course not,’ Alice replied very readily: `but that’s because it stays the same year for such a long time together.’
`Which is just the case with mine,’ said the Hatter.
Alice felt dreadfully puzzled. The Hatter’s remark seemed to have no sort of meaning in it, and yet it was certainly English. `I don’t quit
e understand you,’ she said, as politely as she could.
The Mad Hatter is just full of remarks like that and interestingly enough; Lewis Carol had a very definite role model in mind when he created the character. In 19th century England (and the United States), hatters (people who made hats) really did go mad. Many hats were (and still are) made of felt and the chemicals used to cure felt included mercury nitrate. Prolonged exposure to these mercury vapors caused mercury poisoning. Victims developed severe and uncontrollable muscular tremors and twitching limbs, called "hatter’s shakes"; other symptoms included distorted vision and confused speech. Advanced cases developed hallucinations and other psychotic symptoms.
Many hats were made of beaver fur, but cheaper ones used rabbit fur instead. Making a rabbit fur hat was complex and involved many steps. One step was to brush a solution of mercury nitrate on to the fur to roughen the fibers and make them mat more easily. The process called carroting because it made the fur turn orange. Beaver fur has natural serrated edges that make this unnecessary, one reason why it was preferred, but the cost and scarcity of beaver meant that other furs had to be used.
Whatever the source of the fur, the fibers were shaved off the skin and matted into felt; which was later immersed in a boiling acid solution to thicken and harden it. The acid treatment decomposed the mercury nitrate to elemental mercury. Finishing processes included steaming the hat to shape and ironing it. In all these steps, hatters working in poorly ventilated workshops would breathe in mercury vapor. This hazard continued into the 20th century and it wasn’t until 1941 that the US officially banned the practice of using mercury to make hats.
From Maya Blue to the Mad Hatter. It really is true that when you pick up one end of the universe, you find that everything else is attached to it!
Cruise on over to the Deep Website at www.thedeepradioshow.com to learn more about blue jeans, Maya Blue, Mad Hatters and many other topics. Enjoy