When dipping toast into a cup of tea leads to a scientific investigation

10.1119/10.0000025.1This article recounts a scientific investigation that started from the observation of an ordinary everyday phenomenon. In a cup of tea, dipping buttered toast produces on the surface of the tea beautifully evolving lenses, which are pierced repeatedly by moving holes. To unravel this dynamic observation, we show here how we simplified the system into its basic ingredients, and how we excluded several hypotheses such as thermal convection. We reproduce the phenomenon with an inverse emulsion of surfactant-laden water droplets. Depending on the spreading of the lens, we also observe and explain the formation of an oil lacework and “swimming” lenses.10.1119/10.0000025.1This article recounts a scientific investigation that started from the observation of an ordinary everyday phenomenon. In a cup of tea, dipping buttered toast produces on the surface of the tea beautifully evolving lenses, which are pierced repeatedly by moving holes. To unravel this dynamic observation, we show here how we simplified the system into its basic ingredients, and how we excluded several hypotheses such as thermal convection. We reproduce the phenomenon with an inverse emulsion of surfactant-laden water droplets. Depending on the spreading of the lens, we also observe and explain the formation of an oil lacework and “swimming” lenses.