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No. 2119:
Casting and Optics

Today, we see into the Renaissance. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The Renaissance is often portrayed as a new way of seeing. Maybe that should be taken more literally than we realize. It's often dated from 1455, when Gutenberg printed his Bible, but I think precursors are every bit as interesting as events themselves. And the mechanics of seeing (applied optics) had been bubbling away for two and a half centuries leading up to Gutenberg and his Bible. 

Roger Bacon had suggested the idea of eyeglasses in the early thirteenth century, and a Florentine inventor had actually begun making them seventy years later. Down through the 1300s, glasses were in wide use. And, in a classic technological revenge effect, scribes reacted by using smaller and smaller handwriting to stretch their expensive parchment. 

Eyeglasses in 1494A general fascination with optics was also in the air. Philosophers argued over the mechanics of sight: Do our eyes send out rays that return with information, or do they just catch incoming rays? Is the word of God distorted when it's read through lenses? We find such arguments strange, but they were gradually leading toward a new visual realism. Then, in the early 1400s spherical mirrors captured the public's fancy. A convex mirror catches a fisheye view of the world -- wider than our peripheral vision. 

Jan van Eyck used that idea in 1434 when he painted his Arnolfini Wedding.The young merchant Arnolfini stands with his betrothed in her lovely green dress, greeting us as we enter their house. But van Eyck added an extraordinary flourish. On the rear wall, a spherical mirror captures the entire room. It reveals details we don't see straight on. He makes his own fascination with optics very clear in the painting.

Two years earlier the spherical mirror had gained great popularity in the pilgrimage city of Aix-la-Chapelle -- present-day Aachen. People there decided those mirrors could capture the holy rays of all the relics in the city. 1439 found Gutenberg working secretly with two partners to make sale goods for pilgrims. For a long time, historians guessed they were inventing printing so they could sell indulgences at a great profit. They probably were, but the only existing printed indulgences are from later.

But we do know they developed a casting process to make cheap spherical mirrors from a tin alloy. The mirrors were mounted so pilgrims could pin them to their hats, then go about collecting holy rays from every angle. That's significant because fine casting would be the heart of Gutenberg's printing operation. His printing depended entirely on his ability to cast thousands of metal letters so they'd fit together with a jeweler's precision. 

So we're back to the Renaissance. It was indeed a new way of seeing. And, if we go back to the years before Gutenberg, we find an amazing web of connection between seeing through optics, and eventually seeing through the availability of the printed word.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

For more on these ideas, see: J. H. Lienhard, How Invention Begins: Echoes of Old Voices in the Rise of New Machines. (New York: Oxford University Press, 2006), Chapters 9, 10, 11.

The Arnolfini Wedding 

Image sources:

The fool wearing glasses is a detail from an image in Das Narrenschiff, Sebastian Brant, 1494. (taken from a 1497 Latin translation, courtesy of Special Collections, Univ. of Houston Libraries)

The image of the Arnolfini Wedding painting is from J. C. M. Weale, Van Eyck. (London, T. C. & E. C. Jack, ca. 1912): pg. 40; and the detail of spherical mirror is from W. H. J. Weale and M. W. Brockwell, The Van Eycks and Their Art. (London, John Lane, The Bodley Head, MCMXII): Plate XXV.