Chemists put the colour-changing ‘ouzo effect’ under the microscope

The mystery of the ‘ouzo effect’ – where water added to the clear alcoholic spirit suddenly turns the entire drink milky white – has been explored in greater depth by chemists using a specialised electron microscope. The team behind the work hope that it could lead to better emulsions in instances like paints, drugs and plastics.

Scientists have known for years that the ouzo effect – it’s also seen in similar spirits like pastis – is caused by the drink’s three transparent components: water, ethanol and the anise extract anethole forming a light-scattering emulsion instead of mixing completely. But the resulting emulsion is not well understood and the fact that it’s highly stable and doesn’t need a fourth chemical – a surfactant to stabilise the interface of the components – makes the ouzo effect even more curious.