Phenomena

Speeding Sedimentation

Particles settle faster in a container with inclined walls than one with vertical walls.

Did you know that particles settle faster in an inclined container instead of a vertical one? This sedimentation phenomenon is known as the Boycott effect, after the researcher who first described it. Boycott noticed that red blood cells settled out of samples faster when the test tubes were inclined.

The inclined walls give particles a much larger area to settle on. As the particles gather on the wall, it creates a buoyant, particle-free layer of fluid above. That fluid quickly rises to the top of the container, helping to push the sediment further toward the bottom. As you can see in the video below, the Boycott effect drastically reduces settling time. (Video and image credit: C. Kalelkar)

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