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No. 802:

Today, eerie drawings bind concept to reality. 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 word "blueprint" is a little like the word "coach." The old name carries into so many modern technologies that we forget that the original is gone. Once we made working drawings on a hard translucent paper called vellum. Then we laid the vellum on light-sensitive paper and ran it by a bright light. The exposed paper turned deep blue. The lines stayed white.

Now here's the catch: The last time I made a real blueprint from one of my drawings was 1948. So I've been asking friends, "When was the last time you saw a blueprint?" Most of them tell me, "The day before yesterday." Most people know exactly what blueprints are and think they're still in use.

If you really have seen one lately, it had to be in an old archive. Blueprints died out during the '50s. They were replaced by related processes like Ozalid and blueline.

John Herschel, son of astronomer William Herschel, invented blueprinting in 1842. He too was a great astronomer. He was a mathematician, chemist, and inventor as well. Herschel was the first Englishman to take up photography. After Herschel, blueprinting changed little for 120 years. Maybe, as a child, you photographed leaves by laying them on blueprint paper in the sun.

But by 1960 those ghostly negative images, white on blue, gave way to more obvious pictures with dark lines on a white field. Machinists no longer had to invert images in their minds before they carved them into wood and steel. Still, the people I talk to cannot quite forget those ectoplasmic negative realities.

A friend recently handed me a remarkable book of 26 designs along with their blueprints. Grand Central Station and the Spirit of St. Louis. The Volkswagen Beetle and Washington Cathedral.

Look at the plans for Hoover Dam. They reveal a massiveness we cannot see in Arizona. The dam is as thick at its base as it is high. In Arizona we see the tips of its intake towers floating like water lilies behind the dam's delicate lip. The feathery mass of the white on blue plan is barely kin to the porcelain appearance of the real thing.

So blueprint has become more than a word -- more than an apt icon for a plan, or an intent, or a hope for the future. Those eerie negative images remind us that, when we invent, we see darkly -- as through a glass.

The thing in the mind and the thing in the world are curiously disjunct. But that's where genius enters. Great designers create two realities at once. Good design is hard just because it means building a blueprint in the mind -- for an engine that must one day live and act in the corporeal world.

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

(Theme music)

Gray, C., and Boswell, J., Blueprints: Twenty-Six Extraordinary Structures. New York: Simon and Schuster, 1981.

Encyclopedia of Architecture: Design, Engineering, and Construction (J.A. Wilkes, editor-in-chief,). Vol. 2, New York: John Wiley and Sons, 1988, pp. 246-250.

See also the Oxford English Dictionary entries under "blueprint," "Ozalid," and "diazo."

I am grateful to Margaret Culbertson, UH Library, for her suggestions and help with this episode.