Goethe's Prism: The Colour Theory Physicists Rejected

Goethe looked through a prism at a white wall and saw nothing. No red, no violet, no rainbow. Just a white wall, a little displaced from where it should have been.

That was the problem. Newton's account said a prism turns white light into a fan of seven colors. Goethe's own eyes said otherwise, and he argued that Newton had it backwards. He published his case in 1810 as Zur Farbenlehre. Physics went with Newton.

Goethe was wrong that Newton's account of light was false. But the book is a sharp piece of looking, and a good deal of what he noticed is still what designers rely on when they pick colors for a screen.

The wall that stayed white

Newton's famous setup was a darkened room. According to David Brewster's biography, Newton cut a hole in his window shutter, let in one thin beam of sun, and sent it through a prism onto the opposite wall. The beam spread into a stretched-out spectrum about five times longer than it was wide. Newton counted seven colors in it. His claim, first published in 1672 and laid out in full in Opticks in 1704, was that white light is a mixture of rays that bend by different amounts.

Goethe took the opposite approach. He did not start with a beam in the dark. He started with a room full of ordinary light and looked at ordinary things.

In the English translation, his observation reads like a lab note. Look at "a uniformly white or coloured wall through a prism" and the surface shifts position, "without our therefore observing the smallest appearance of colour" (§196). Color shows up only "at the outlines or boundaries" where the surface meets something darker or lighter (§197).

He was right about what he saw. Prism viewers report the same thing: colored fringes along the boundaries and plain white or gray in the middle of a broad surface. His conclusion went further. Color, he argued, is not hiding inside white light. It appears where light and dark meet. Newton's tidy spectrum was, to Goethe, a special case produced by a narrow beam, which he called a "secondary phenomenon" mistaken for the root one (§176).

A scholarly commentary notes that Newton's green-centered spectrum appears at one particular distance between prism and screen. Move the screen closer and you see two separate edge spectra, which is closer to what Goethe described. The abstract concludes that both accounts fit a lot of the data. The disagreement was about what counts as the basic fact, not about whether either man saw what he said he saw.

Why the physicists walked away

Newton's model gave a mechanism you could test. In Brewster's account, a second prism turned the stretched spectrum back into a round spot of light, which showed the colors were not an accident of the glass. Goethe's model made you look harder, and it offered no mechanism.

So his optics lost. Cambridge's Whipple Library calls Opticks "the most influential analysis of the physical behaviour of light". Goethe, on the other hand, had written something else: a long record of how color behaves for an eye in a room.

That second book is the useful one.

Blue shadows and the candle test

Goethe's chapter on colored shadows is the part you can test tonight. Put a white sheet of paper on a table, light a candle, and let daylight fall on the paper at the same time. The shadow the candle throws will look blue.

He explained why in §66: the candlelit paper reads as reddish-yellow, and the eye supplies the opposite color, blue, in the shadow. He also noted that a shadow in plain sunlight on a white surface "appears black" with no color at all (§63), and he said colored shadows need two conditions to appear (§64).

This is the same effect designers now meet as simultaneous contrast, and its cousin, the afterimage. Goethe called these "physiological colors" because "they belong to the eye in a healthy state" (§3). Before him, he says, such colors were too fleeting to pin down and were "banished into the region of phantoms" (§1).

His complementary pairs are the ones on any modern wheel: "yellow demands purple; orange, blue; red, green" (§50). If you want to see how far that idea travels, read about why hospital scrubs are teal. The reasoning there is Goethe's, applied to an operating theatre.

Why the sky is blue, according to a poet

Goethe had a second idea, and this one holds up better than his optics. He thought color comes from light seen through a cloudy medium. Look at the dark through a lit haze and you get blue. Look at light through the same haze and you get yellow, then red as the haze thickens.

He wrote it down plainly. Darkness seen through a semi-transparent, illuminated medium shows blue (§151). On high mountains the sky looks deeper blue because there is less vapor in front of the dark beyond (§155). And "the red hues of morning and evening" come from the same cause: the sun's light crossing a thicker layer of vapor (§154).

The modern account is different in its machinery. Air molecules scatter short wavelengths more than long ones, an effect named for Lord Rayleigh. The sky is blue because blue light gets scattered all around us. A low sun looks red because its light has crossed so much air that most of the blue is gone.

The prediction, though, is nearly the same as Goethe's. Blue overhead, red at the horizon, and a deeper blue the thinner the air. He got the pattern right and the cause wrong, which is a decent record for a man writing before the physics existed.

That pattern is useful in practice. It is the reason cool colors sit back and warm ones come forward, a trick covered in color temperature and depth. A blue background in an interface reads as distant air. A yellow or orange button reads as the sun.

Plus and minus: the first mood board

The last part of the book is the one designers quote. Goethe sorted colors onto two sides of a circle and described what each side does to a viewer. The sections run from §764 to §799.

The plus side is yellow, red-yellow and yellow-red. Yellow gives "a warm and agreeable impression" (§768). Red-yellow brings warmth and gladness, which he tied to firelight and the setting sun (§773). Push it further to yellow-red and it becomes intensely exciting. He reports that "a yellow-red cloth disturbs and enrages animals" (§776).

The minus side is blue, red-blue and blue-red. Blue carries "a principle of darkness" (§778), and its effect is "a kind of contradiction between excitement and repose" (§779). Looking through blue glass, he says, makes things look gloomy and melancholy (§784). Red-blue is restless, which is why he thought it should be used sparingly in dress (§§787, 790).

These swatches are my approximations of his two sides, not his own paint chips. The point is the split. It is an early version of how we talk about warm colors today, and of the warm and cool coding that runs through nearly every color wheel. It also gave painters a working vocabulary.

The painter who annotated it

Goethe's book reached English readers in 1840, when the painter Charles Lock Eastlake published a translation with John Murray in London. Eastlake was a friend of J.M.W. Turner, and a scholarly study of the pair reports that Turner annotated his copy.

Tate confirms that Turner owned an English translation of the Theory of Colours and heavily annotated it. It adds that Turner was drawn to the plus and minus split. In 1843 he exhibited a painting with Goethe's name in the title: Light and Colour (Goethe's Theory), the Morning after the Deluge. Tate describes it as a decidedly "plus" palette, with warm yellows used to suggest a spiritual reawakening. A companion, Shade and Darkness, the Evening of the Deluge, was shown the same year.

Turner did not illustrate Goethe like a textbook. He used the plus and minus idea as a plan for how a picture should feel. Warm for hope, cold for dread. That is a color script, which is the same job a modern studio gives a Pixar color script.

What to take from a wrong theory

You do not need Goethe's optics. You need three of his habits.

1. Look at the edges. Color changes most where two areas meet, so test any palette at the borders, not just in the swatches. A contrast checker will tell you if the numbers work, but your eye tells you how the edge feels.
2. Expect the eye to add color. A gray beside a saturated orange will lean blue. If your palette looks off, the neighbors are probably doing it.
3. Sort your colors by mood before you sort them by hue. Ask which of your swatches sit on the warm, advancing side and which sit on the cool, retreating side. Then check the balance with the palette generator. Our color theory reference covers the vocabulary if you want to go further.

Goethe was wrong about the physics and right about the eye, which is the half of color that designers get paid to understand.

Sources

• Goethe's Theory of Colours, translated by Charles Lock Eastlake (John Murray, London, 1840), Project Gutenberg
• Goethe's Theory of Colours, translated from the German, Royal Academy of Arts library record
• Isaac Newton's Opticks, Whipple Library, University of Cambridge
• A. C. Sparavigna, The play of colours of prisms (quoting David Brewster's account of Newton's prism experiment), arXiv
• Goethe and Newton on colour, PhilArchive abstract
• Why is the sky blue?, Royal Museums Greenwich
• C. S. König and M. W. Collins, Goethe, Eastlake and Turner: From Colour Theory to Art, International Journal of Design & Nature and Ecodynamics, 2009
• How to spin the colour wheel, by Turner, Malevich and more, Tate
• Light and Colour (Goethe's Theory) - the Morning after the Deluge, J.M.W. Turner, exhibited 1843, Tate