In this short film from the Chemical Bouillon team, dark ink drops spread in dendritic fractal patterns after being deposited on an unknown transparent liquid. Although the patterns look similar to those of the Saffman-Taylor instability, I suspect what we see here is actually driven by surface tension and not viscosity.
The authors describe the ink they used as a “special old” “tree ink,” which — putting on my fountain pen aficionado hat — probably means some variety of iron gall ink. These inks draw on chemicals extracted from trees and other plants to create a permanent, waterproof ink. They tend to be highly acidic, which could play a role in the pattern formation seen here. (Video and image credit: Chemical Bouillon)
Steve Grimmer
There’s a pottery decoration technique called Mocha Diffusion that produces this phenomenon. The applied stain is rather acidic, like iron gall ink.
Nicole Sharp
Neat! I bet there’s similar underlying chemistry helping to drive the instability.
Hassan dastani
I developed a technique that grows dendrite patterns on anything like glass, iron, plastic, rock, and even plants and wood.