The instrument of intellectuals
For the world’s mathematicians, the ultimate luxury is a piece of fine Japanese chalk.
Hagoromo Fulltouch Chalk, beloved for the smooth, dense texture that makes proofs and equations seem to flow with ease, is the subject of a short documentary in which math professors rhapsodize over its seemingly magical properties. “The legend around this chalk is that it’s impossible to write a false theorem,” one man declares. In 2014, educators began stockpiling supplies when the Hagoromo manufacturer announced it was shutting down due to dwindling demand after more than 80 years in business. Salvation came when a Korean company swooped in to purchase Hagoromo’s machines and formula.
Chalk has been disrupted by whiteboards and interactive displays, but it still has a devoted fan base. Put a good piece of chalk in a person’s hand, and inspiration seems bound to strike — as evidenced by everything from Renaissance-era artwork to DIY crafters’ modern-day affinity for chalkboard paint.
Let’s wipe the slate clean and settle in for a tutorial on the Earth’s natural tool of communication.
By the digits
3: Types of natural chalks: white (made from limestone), red (made from red ochre and other earths), and black (made from shale)
16: Number of massive horse-shaped geolyphs in Britain, carved into the area’s grassy hills by cutting into the chalk beneath the surface
90 million: Sticks of chalk produced annually by Hagoromo at its peak in 1990
45 million: Sticks produced annually by Hagoromo before its decision to close in 2014
$70.5 million: 2015 auction price for a painting in artist Cy Twombly’s Blackboard series, which uses paint and crayon on canvas to mimic the appearance of chalk scribbles on a blackboard
Origin story
The power of “chalk and talk”
Chalk has been a favored material for writing and drawing since cavemen began using it for paintings during the prehistoric era, and paired with tablets as a tool for classrooms since at least 11th-century India. But it was only in the early 1800s that teachers began writing on large chalkboards at the front of the room — a technological shift that gave them a far more efficient way of presenting ideas and problems to students.
Among the early innovators was Scottish education reformer James Pillans, who said that his objective in using blackboards was to “make a strong impression on the eye, and to set the imagination and conception to work.” To that end, Pillans also invented colored chalk, using a recipe of ground chalk, dyes, and porridge to add visual complexity to his geography lessons.
Across the pond, George Baron, a mathematics instructor at West Point military academy in the U.S., was another founding father of the “chalk and talk.” By 1809, every public school in Philadelphia had adopted blackboards — a testament to the technique’s ability to engage students, according to Lewis Buzbee’s Blackboard: A Personal History of the Classroom. “Students no longer simply listened to the teacher; they had reason to look up from their desks,” Buzbee writes.
So transformative was this new technology that one 1841 teaching manual declared, “The inventor or introducer of the black-board system deserves to be ranked among the best contributors to learning and science, if not among the greatest benefactors of mankind.”
Quotable
“A great chapter of the history of the world is written in the chalk.” — Thomas Henry Huxley in the 1868 essay “On a Piece of Chalk”
What’s so great about chalk?
Historically chalk was made from calcium carbonate — the crushed skeletons of tiny sea algae called coccolithophores. Much blackboard chalk in use today is made from gypsum, or calcium sulfate, which is cheaper and more abundant than calcium carbonate; calcium carbonate is still used in so-called “dustless” chalk.
Greenboards, coated with a porcelain enamel paint, became popular during the mid-20th century, valued for their appealing color and for cutting down on glare from the sun. But the bell tolled for chalkboards with the advent of whiteboards, which addressed concerns over the deleterious effects of chalk dust for human lungs, computers, and general classroom cleanliness.
Still, some educators say there’s no substitute for the magic that happens when chalk meets board. Like mathematicians, physicists are known to cling to their chalk. It is practical, after all. Dry-erase markers, run out, dry up, and sometimes leave behind the ghosts of equations if they’re not erased promptly or with a spray — not quite living up to the promise of their name.
But some of the appeal of chalk is a philosophical, tangible joy in the material. “An idea captured in chalk is composed of infinitely many fine particles of dust, which makes it natural to rearrange it in different patterns, whereas the thick black tar emitted by whiteboard pens makes the idea sticky and harder to work with,” theoretical physicist Peter Skands told Symmetry.
Brief history
100 AD: The Romans use chalk to make buildings and roads.
1438: The first documented sale of chalk is reported, noting that the Bishop of Châlons in France wanted to use it to whitewash some buildings.
16th century: Leonardo da Vinci helps popularize pastel painting, which relied on pastels made from chalk kneaded with pigment powder and a binding material.
1814: Scottish educational reformer James Pillans is credited with the invention of colored chalk and the classroom blackboard.
1840s: Blackboards can be found in nearly every U.S. classroom.
1902: Binney & Smith (now Crayola) introduces a dust-free chalk for schools, which wins a gold medal at the St. Louis World Exposition.
1930s: Green chalkboards, made with a porcelain-enameled paint, are offered as a cheaper alternative to traditional black slate boards.
1960s: The first whiteboards appear on the market, although they will not become popular for several decades.
1975: The first dry-erase marker is patented.
2018: Over 75% of K-12 classrooms in the U.S. have interactive whiteboards.
Fun fact
The notoriously jarring sound of fingernails on a blackboard has a frequency that’s amplified by the human ear canal, so it’s especially piercing. It’s possible that this is an evolutionary adaptation, as that frequency range also includes screams.
Pop quiz
What do you prefer writing on?
- A chalkboard
- A whiteboard
- I’m all digital baby
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Today’s email is a rerun of a previous Obsession that was written by Sarah Todd, edited by Whet Moser, and produced by Luiz Romero. It includes updates from Morgan Haefner.