Kaye effect

[1] While pouring one viscous mixture of an organic liquid onto a surface, the surface suddenly spouted an upcoming jet of liquid which merged with the downgoing one.

The effect usually goes unnoticed, however, because it seldom lasts more than about 300 milliseconds.

The effect can be sustained by pouring the liquid onto a slanted surface, preventing the outgoing jet from intersecting the downward one (which tends to end the effect).

Whilst it was long thought to occur due to a shear-thinning slip layer,[2] recent studies have shown through high-speed videos[3] and experiments in a vacuum chamber[4] that an extremely thin layer of air (approximately 1000 times thinner than the jet diameter) is entrained, which acts as a lubricant and supports the sliding jet.

In a jet viscoelastic fluid, a portion of the energy of deformation as the jet falls is recoverable, and this reduces the force required to support the leaping jet, enabling more air to be entrained.