Beyond the ink: Painting with physics

Okinawa Institute of Science and Technology (OIST) researchers got down to analyse the physical principles of this fascinating technique, referred to as dendritic painting. They took inspiration from the artwork of Japanese media artist, Akiko Nakayama. During her live painting performances, she applies vibrant droplets of acrylic ink mixed with alcohol atop a flat surface coated with a layer of acrylic paint. Beautiful fractals — tree-like geometrical shapes that repeat at different scales and are sometimes present in nature — appear before the eyes of the audience. This can be a fascinating art form driven by creativity, but additionally by the physics of fluid dynamics.

“I actually have a deep admiration for scientists, similar to Ukichiro Nakaya and Torahiko Terada, who made remarkable contributions to each science and art. I used to be very glad to be contacted by OIST physicist Chan San To. I’m envious of his ability ‘to dialogue’ with the dendritic patterns, observing how they alter shape in response to different approaches. Hearing this secret conversation was delightful,” explains Nakayama.

“Painters have often employed fluid mechanics to craft unique compositions. We’ve seen it with David Alfaro Siqueiros, Jackson Pollock, and Naoko Tosa, simply to name a couple of. In our laboratory, we reproduce and study artistic techniques, to grasp how the characteristics of the fluids influence the ultimate consequence,” says OIST Professor Eliot Fried of OIST’s Mechanics and Materials Unit, who likes taking a look at dendritic paintings from artistic and scientific angles.

In dendritic painting, the droplets fabricated from ink and alcohol experience various forces. Considered one of them is surface tension — the force that makes rain droplets spherical in shape, and allows leaves to drift on the surface of a pond. Particularly, as alcohol evaporates faster than water, it alters the surface tension of the droplet. Fluid molecules are inclined to be pulled towards the droplet rim, which has higher surface tension in comparison with its centre. This is known as the Marangoni effect and is identical phenomenon liable for the formation of wine tears — the droplets or streaks of wine that form on the inside a wine glass after swirling or tilting.

Secondly, the underlying paint layer also plays a very important part on this artistic technique. Dr. Chan tested various forms of liquids. For fractals to emerge, the liquid should be a fluid that decreases in viscosity under shear strain, meaning it has to behave somewhat like ketchup. It’s normal knowledge that it’s hard to get ketchup out of the bottle unless you shake it. This happens because ketchup’s viscosity changes depending on shear strain. If you shake the bottle, the ketchup becomes less viscous, making it easier to pour it onto your dish. How is that this applied to dendritic painting?

“In dendritic painting, the expanding ink droplet shears the underlying acrylic paint layer. It will not be as strong because the shaking of a ketchup bottle, nevertheless it remains to be a type of shear strain. As with ketchup, the more stress there’s, the simpler it’s for the ink droplets to flow,” explains Dr. Chan.

“We also showed that the physics behind this dendritic painting technique is comparable to how liquid travels in a porous medium, similar to soil. In the event you were to take a look at the combo of acrylic paint under the microscope, you’d see a network of microscopic structures fabricated from polymer molecules and pigments. The ink droplet tends to seek out its way through this underlying network, travelling through paths of least resistance, that results in the dendritic pattern,” adds Prof. Fried.

Each dendritic print is one-of-a-kind, but there are a minimum of two key points that artists can consider to regulate the consequence of dendritic painting. The primary and most significant factor is the thickness of the paint layer spread on the surface. Dr. Chan observed that well-refined fractals appear with paint layer thinner than a half millimetre.

The second factor to experiment with is the concentration of diluting medium and paint on this paint layer. Dr. Chan obtained essentially the most detailed fractals using three parts diluting medium and one part paint, or two parts diluting medium and one part paint. If the concentration of paint is higher, the droplet cannot spread well. Conversely, if the concentration of paint is lower, fuzzy edges will form.

This will not be the primary science-meets-art project that members of the Mechanics and Materials Unit have launched into. For instance, they designed and installed a mobile sculpture on the OIST campus. The sculpture exemplifies a family of mechanical devices, called Möbius kaleidocycles, invented within the Unit, which can offer guidelines for designing chemical compounds with novel electronic properties.

Currently, Dr. Chan can also be developing novel methods of analysing how the complexity of a sketch or painting evolves during its creation. He and Prof. Fried are optimistic that these methods is perhaps applied to uncover hidden structures in experimentally captured or numerically generated images of flowing fluids.

“Why should we confine science to only technological progress?” wonders Dr. Chan. “I like exploring its potential to drive artistic innovation as well. I do digital art, but I actually admire traditional artists. I sincerely invite them to experiment with various materials and reach out to us in the event that they’re concerned about collaborating and exploring the physics hidden inside their artwork.”

Instructions to create dendritic painting at home

Everybody can rejoice creating dendritic paintings. The materials needed include a non-absorbent surface (glass, synthetic paper, ceramics, etc.), a brush, a hairbrush, rubbing alcohol (iso-propyl alcohol), acrylic ink, acrylic paint and pouring medium.

1. Dilute one a part of acrylic paint to 2 or three parts of pouring medium, or test other ratios to see how the result changes
2. Apply this to the non-absorbent surface uniformly using a hairbrush. OIST physicists have discovered that the thickness of the paint affects the result. For one of the best fractals, a layer of paint thinner than half millimetre is beneficial.
3. Mix rubbing alcohol with acrylic ink. The density of the ink may differ for various brands: have a try mixing alcohol and ink in numerous ratios
4. When the white paint remains to be wet (hasn’t dried yet), apply a droplet of the ink with alcohol mix using a brush or one other tool, similar to a bamboo stick or a toothpick.
5. Enjoy your masterpiece because it develops before your eyes.