Was cleaning a stain and it occurred to me it should be evenly spread, however the edge is thicker and harder to clean than the center of the stain.
In: Biology
At the risk of being completely wrong, I’m going to just add a theory. Maybe when it lands, the ripple effect pushes more of it to the edges, like a tiny wave. And because blood is thicker than water (awesome), not as much redistributes itself to even out?
The edge evaporates first because it has a greater surface area. The solids there congeal and become harder to clean off than the still-dissolved ones in the center.
This is a known physical phenomenon commonly called “the coffee ring effect”.
As liquid evaporates on the edge of a droplet, capillary effects cause liquid to flow from the center of the droplet to the edge, carrying dissolved or suspended solids with it.
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