Monday, September 5, 2011

Saussure’s Cyanometer

Swiss alpinist Horace-Bénédict de Saussure (1740-1799) wondered how the blue of the sky changes with altitude.

He observed that the color of sky was lighter close to the horizon. He suspected that the blue would get darker at higher altitudes, but how much darker? Legend had it that if you climbed to the tops of the Alpine peaks, the sky would be black, and there was a risk of “falling into the void.”

So he made a “cyanometer,” by dipping swatches of paper into a suspension of Prussian blue in order to obtain nearly sixty evenly spaced swatches of blue ranging from white to black. 

In 1787, Saussure hired two guides and undertook a three-day trek to the 15,780-foot summit of Mont Blanc. When he tested his cyanometer against the sky, it matched swatch 39, the darkest he had ever seen.

Although our modern understanding of scattering of light by air molecules still hadn’t been completely figured out, Saussure had made an important breakthrough. On top of a very tall mountain, there is less air above the observer to scatter the sunlight and produce a blue veil over the blackness of space.

When I painted the temple on the highest peak of Dinotopia, I made sure to use a darker blue for the sky, and a more abrupt transition above the horizon.

Full story of Saussure's Cyanometer at the RCS Chemical Sciences website
Wikipedia on Saussure
Wikipedia on Mont Blanc
Previously: How to make your own cyanometer from blue paint chips from the hardware store
Reproduction of Palace in the Clouds in Imaginative Realism
More about "sky blue" in Color and Light
Palace in the Clouds from Dinotopia: A Land Apart from Time - The 20th Anniversary Edition
Thanks, Tancredi


Jean Wogaman said...

That's such a beautiful picture, one of my favorites!

Tim Fitzgerald said...

Thanks for that,very helpful!!

Krystal said...

As usual, this piece of information is awesome... as is the picture. I am litteraly in love with it !

Tati said...

I've always noticed that in Hokusai's works but they are even more abrupt, such as:

Unknown said...

Awesome post! Are you sure you shouldn't have trekked up some 15k high mountain to double-check things? LOL!

JonInFrance said...

Do you know the Little Big Adventure/Relentless video game from the late 90s Jim?

Unknown said...

I love those 18th century explorers: instead of looking at Google for their answers ;-), they built ingenious devices to experiment and to get an answer to their question...!

David Teter said...

I can't imagine trekking up some mountain way back then... and at 47 years old too! I'll bet he was thrilled when holding up his meter.
Love your painting, there I would go, since I could sit by a fireplace... right? you did put fireplaces in didn't you?

Damon Taylor said...

Love all these little history lessons James, very interesting, keep 'em coming!

Ernest Friedman-Hill said...

There's a story on Hackaday today about a homebrew high-altitude balloon flight; there's a beautiful photo showing the sky from 31 km fading through beautiful blues all the way to black:

Pancho said...

really really usefull in fact!
I don't know nothing about this, but is very important. thank you, man.

Student Service said...

...and I've been called 'anal' with color swatches :)

colourblynde said...

Hello Mr. Gurney! Just dropping by to leave a little comment. I grew up reading Dinotopia... my mom and I would spend hours together just sitting, reading the books. I distinctly remember looking at the covers and trying to draw a Skybax. From then on, I started to doodle in middle and high school, and eventually found my way to an art college. Now in my sophomore year, one of my professors linked me to your page as a good reference for colour and inspiration... and I was blown away. Seems like everything comes full circle at one point! Thank you so much for everything. :D

James Gurney said...

Colourblynde, thanks for saying hello. Yes, all things seem to come full circle. Good luck to you in your art.

JoninFrance, No, I'm not familiar with that.

David, yes, they've got roaring hearths up there, but it's a job to bring up the firewood.

Thanks, all for your great comments.

Unknown said...

This is amazing! Such a beautiful way to test out his theory as well.