Mini Stories: Volume 5

Photo by Megan Eaves (CC BY 2.5)

The Cerulean Process by Emmett Fitzgerald

US history is filled with stories of medical quackery. And while most cure-alls were elixirs sold in bottles, we came across a strange, architectural panacea. For a brief time, back in the 1870s, some people thought that blue windows were the solution to just about every medical problem you could think of. The main purveyor of this belief was a Civil War general named August Pleasanton.

Pleasanton was something of an armchair scientist, and in between his military duties, he would read lots of books on physics and botany. Over time he developed some pretty strange opinions, but his strangest was about the color blue.“I have long thought that the blue color of the sky, so permanent and all-pervading […] must have some abiding relation and intimate connection with the living organisms on this planet,” Pleasanton declared. He began to argue that he could actually speed up growth in plants using blue light.

To test this hypothesis, Pleasanton built a giant greenhouse. It looked like a standard greenhouse, except that some of the panels in the roof were made of blue glass in order to let in a certain amount of “blue light.” In this “blue house” he grew grapes, and got some incredible results. He reported massive growth, huge vines and tons and tons of grapes.

August Pleasanton’s blue glass grapery via Internet Archive

After that initial success with grapes, Pleasanton started raising pigs and cows beneath blue glass panels. Word got out and soon he was being asked to give talks about his experiments. He extolled the virtues of blue light not just for raising grapes or pigs, but humans. He said that blue light caused an electrical current to flow through the body and invigorate the organs solving all kinds of physical deficiencies.

The Influence of the Blue Ray of the Sunlight and of the Blue Color of the Sky by Pleasanton (via Internet Archive)

Pleasanton received a patent for his “cerulean process,” and he published a whole book about the value of blue light.

Pleasanton touted blue light as a cure-all for all sorts of human ailments—from skin conditions, to baldness, to insomnia. The book was popular, and soon people all over the country were demanding blue glass. “For about two years, 1876 and 1877, there [was] suddenly this huge fad for all things blue,” says Jenny Benjamin, curator of the Museum of Vision in San Francisco. People bought blue eye glasses and blue wallpaper, but the most common purchase was blue windows. People wanted to create a place in the house where you could go bathe in the blue light.

The “blue glass craze” was ultimately short-lived. Scientific American very publicly debunked Pleasanton’s wild claims, and people eventually stopped buying blue windows. There may still be some homes from that era out there with their original blue glass windows — we just haven’t found them yet!

Google Street View image from 2017 of a potential original blue glass window. The building pictured is no longer standing today. Screenshot via Emmett Fitzgerald.

Special thanks to Bart Bernhardt co-founder of Nerd Nite SF who wrote in with this story suggestion.

Comments (4)


  1. jschuh

    umm, a solar powered flashlight isn’t exactly useless you know…
    just in case Viv doesn’t get it, it charges when you don’t need it…

  2. Hello 99 PI,

    Articles or principles of a manifesto or a constitution are tenets. Unless these principles are only contract residents of the doctrine, then they may be tenants.

  3. Dan

    Re blue glass: I can’t see a window pane from the street view image, but there is a house in Berkeley that is clearly devoted to blue glass. The architecture looks old enough to me, but you’re the experts. You don’t even need to cross the bridge. Northeast corner of Milvia and Francisco.

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