Cryophorus

A typical cryophorus has a bulb at one end connected to a tube of the same material.

When the liquid water is manipulated into the bulbed end and the other end is submerged into a freezing mixture (such as liquid nitrogen), the gas pressure drops as it is cooled.

Evaporation causes the water to cool rapidly to its freezing point and it solidifies suddenly.

[note 1] Wollaston's cryophorus was a precursor to the modern heat pipe.

[1] The cryophorus was first described by William Hyde Wollaston in an 1813 paper titled, "On a method of freezing at a distance.

Wollaston's diagram of a cryophorus. When the empty ball on the right is immersed in a freezing mixture of snow and salt, the water in the ball on the left freezes in a few minutes.