Insight into\nMocha Diffusion Occurring during Ethanol\nDroplet Spreading on Acrylic Paint

Mocha\ndiffusion, a significant interfacial phenomenon in pottery\npainting, remains insufficiently understood in the documented literature\nregarding its dynamics. This study experimentally investigates Mocha\npatterns by quantitatively dripping ethanol droplets onto an acrylic\npaint surface. Results indicate that the spreading radius increases\nwith the ethanol mass fraction, while the fractal period decreases.\nThe fractal dimension of all Mocha patterns approximates 1.4087. Marangoni\nflow, generated by the volatilization of ethanol, is crucial for the\ngrowth and fractal formation of the “dendrites” in this\nspreading. The scaling analysis is used to interpret the spreading\ndynamics. This work encourages the interface science community to\ndevelop a comprehensive theory for the dynamics of Mocha diffusion\nand highlights the potential of this intriguing decorative technique.