Louching is the term for when a clear spirit suddenly turns cloudy, milky or opaque. It is sometimes also known as the “ouzo effect” or hazing.
It is predominantly associated with Absinthe, which turns cloudy when water is added. This is due to the spirit containing components that are not soluble in water (mainly from the use of fennel and star anise) and the hydration causes them to drop out of solution and turn the drink cloudy - known as the louche.
For Absinthe it is seen as a sign of quality, but for Gin and other spirit categories, the debate is much more polarised as to whether it is a positive or a fault (or if it is confusing to the everyday drinkers). Some argue that botanical intensity and fatty acids are great for flavour and mouthfeel, while others suggest that for the likes of Gin, it is unnecessary to overburden recipes with such dosages and that it’s possible to mitigate against louching through the process the distiller undertakes.
We would suggest that both can be correct and that many mistake boldness for balance, and that the decision for it being a fault or a merit must be taken on a case-by-case basis.
Either way don’t be alarmed by a spirit that louches in your glass, it’s perfectly normal.
See Chill Filtration