Breath figures [8]

Abstract

Glass surfaces are sometimes sparked with a high-voltage high-frequency spark, or flamed, to clean them of organic contamination, and then checked for cleanliness by breathing on the surface. A characteristic 'breath figure' appears, the moisture from the breath condensing in tiny droplets on any hydrophobic contaminated areas, which appear cloudy, but condensing uniformly on the hydrophilic areas to form clear patches. The hydrophilic areas are sometimes thought to be 'clean'1. © 1957 Nature Publishing Group.