Tag Archives: paint

The impermanence of color: the treachery of entropy

Color seems like an easy, marvelous thing when you get that 64 color box of Crayolas as a kid. 64 sticks of pure color. But, of course, color is complicated. It can be impermanent, difficult to obtain, and toxic. To understand the life and chemistry of colors is to peek under the hood. It’s not what catches your eye, but it’s the heart of the drama.

Many paintings are known to be fading; it’s the newer paintings that draw the most concern. To some extent, the older paintings had probably already faded, but the older paintings also used old tried-and-true methods. The works of Jan van Eyck (1390-1441) are considered to be about as colorful today as when they were painted. Van Gogh’s daisies are fading. Renoir’s red has been digitally re-envisioned to show its pre-faded look.

The 1800s were a boom time of chemistry and industrialization, and the art world participated in this expansion too. 12 elements, including sodium and potassium, were discovered between 1800 and 1810. As Chemistry exploded, and new colors exploded. Mauve, the first synthetic dye, was produced in 1856 from coal tar. Renaissance painters (or their apprentices) prepared their own dyes and pigments (think of those scenes from “The Girl with the Pearl Earring” where Scarlett Johansson is grinding various things); 19th century painters bought paint from chemists. Like the disintegrating trade paperbacks of the early 1900s, when industrialization took over an old process, it was faster and cheaper, but took a while to match other characteristics. Books from the early 1800s are often far more intact than the wood-pulp books that followed them.

Artists like Van Gogh knew the strengths and limitations of their new tools. Van Gogh wrote to his brother, noting that the Impressionist paints “fade like flowers,” so he used the brightest colors he could, doing what he could to counteract impermanence. Even now, not all paints are equally durable; here’s a table for watercolors including such measures.

Today, scientists are studying the precise chemistry that causes fading using X-rays. So far, nothing can be done to stop or reverse the fading; they can only be kept away from light. At least we have the tools to imagine their former glory.

Further reading: Victoria Finlay’s Color is a great read on the chemistry of color without diving too deep technically. I reviewed it on this blog a couple of years ago. This article about the history of oil colors is also really fascinating. And finally, if you’re a chemistry buff, the scientific article about Van Gogh’s fading yellow is open source, and available to the public here.

 

 

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Writing prompt: Blame someone else

Time: 10 minutes. Click here to go to my list of prompts.

“Blame someone else” (This list is an awesome source of completely silly prompts.)

 

The painting was covered in a thick layer of soot. I read the documentation. For years, it had hung next to a fireplace in a small poorly ventilated room. But the composition and the brushstrokes had the right look. My boss believed it was an authentic Vensammer. Tina the wonder employee, said that it probably wasn’t. When I cleaned this painting up, she’d see.

I looked at the painting for a while. It depicted a middle-aged woman sitting next to a young boy. In my mind, I guessed at the age of the painting and the techniques that would have been used at the time. Which paints would react to which treatments. If it was a Vensammer, we could auction it for twenty times what we bought it for.

I reached for the solvent, but instead I knocked it over onto the painting. I picked the painting up and tried to let it run off. If it had the proper oil finish, it would be okay with such a brief exposure. I turned the painting back over. It was not. Paint ran in ugly rivulets. Vensammer would never have been so reckless. It wasn’t a Vensammer. It was a worthless piece of junk that I had further ruined.

Quickly quickly, I dried the painting. I slid it back into the storage slot. I carefully redacted my name from the sign in list, and put Tina’s in instead. I took another painting that needed light cleaning and hurried off with it. No sir, I’d never touched that Vensammer.

Tina came in later. She studied the log; she seemed puzzled by it. I said nothing. She pulled out the faux Vensammer.

“Mert, what happened to this painting? I didn’t do this, I swear!” Her eyes were wide, pupils dilated.

The boss walked in. I suppressed a smile. “Is that the Vensammer?” she bellowed.

“Y-yes,” Tina stammered. “I can’t explain.” Tina stared at the painting, desperate. Then her face settled. “Wait,” she said. “Do you see this shape underneath this smear?”

The boss leaned in. She grunted.

“There’s another painting under here!” Tina cried. “And I’m even more certain the surface painting wasn’t a Vensammer.” She pulled out several tools and carefully set to work on the painting. “This shade of yellow… I bet this is an Artello!”

“An Artello! That’s better than a Vensammer!”

Fun science: An easy fractal to make at home

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Viscous fingering is a fractal pattern that occurs when a less viscous (or thick) fluid spreads through a more viscous (or thick) fluid. Such systems are present in oil extraction, when we pump one fluid underground to push another one out. Fractals are common in nature even though they’re new to our mathematics, and they are beautiful.

The pictures in this post were created with basic watercolor paints using one simple principle: water containing paint is more viscous than regular water. It’s easy to try at home!

For the top picture, I laid down red paint. Before the paint dried, I added salt, then let the square dry. Water from the still-damp paper rushed to the salt (because of entropy, systems tend towards uniform distributions of things if they can help it– in this case, the lowest energy state is to have a uniform distribution of salt). But because paint molecules are larger than water molecules, they don’t move as well. The water that accumulates around the salt has less paint than the water in the rest of the paper, and thus we have a less viscous fluid spreading into a more viscous one. Try it at home! If the paint is too wet or too dry when you add the salt, the results won’t be as dramatic, so play around a bit. Larger salt crystals can be especially fun.

For the three pictures below, I simply placed a drop of water into a damp square of paint. The patterns vary depending upon the size of my drop, the wetness of the paint, and the paint color (the chemistry of which influences the viscosity of the paint).

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Below are a couple of examples from the University of Alberta of viscous fingering with pentane into oil and water into oil. This particular research aims to improve the flow rate of oil during extraction. And it looks pretty similar to some humble watercolors.

Left: pentane displacing mineral oil. Right: Water displacing mineral oil (University of Alberta).