A video (above) showing a frozen grape crystallising the water around it when dipped in a glass has social media users wondering how to achieve this interesting result. Supercooling, also known as undercooling, is the phenomenon at work.
Supercooling is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid. The liquid then only solidifies once it finds a nucleus to form a crystal structure around (for example, a frozen grape). Supercooling can be used to make “slushies,” to improve the texture of frozen foods or even to stay warm!
Achieving this at home can be tricky, since supercooling only works with liquids that have no impurities (and can trigger crystallisation). This WikiHow guide explains how to supercool water at home.