Marinated eggs: An engaging quantitative demonstration of diffusion

Marinated or pickled eggs are enjoyed in cultures across the world, and recipes for these eggs use diffusion to saturate the egg white of a hard-boiled egg with sauce. Inspired by the marinated egg, this experiment demonstrates diffusion in an easy and quantitative way. Peeled hard-boiled eggs are placed in a dye solution, and the penetration distance of the dye into the egg white is measured as a function of time using image processing. The penetration distances are consistent with the expected dependence on the square root of time, and the diffusion of the dye occurs faster at higher temperatures as expected. This experiment provides a new way to demonstrate diffusion-based mass transfer visually and to make a connection between physics and culture.