We visualize thixotropy by showing how droplet impact and splashing are significantly affected by aging. Rejuvenated "young" drops pass through meshes, whereas aged "old" drops do not. The results were discovered while studying how thixotropy plays a role in spraying, splashing, and coating with yield-stress fluids, using high-speed video observations. The results are scientifically significant because they show how existing dimensionless groups in fluid dynamics that deal with complex fluids must be modified to include the effect of thixotropy. Educationally, the video represents a unique way to visualize thixotropic aging, a key phenomenon of rheology that has traditionally been difficult to visualize in static images.
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