"Clouds In The Sky" and the Ouzo-effect.

2 cocktails: 8 cl Maraschino, 4 cl ouzo, 6 cl vodka mixed with 2 cl Blue Curaçao, mint leaves, ice.

This is an undeniably wonderful summer drink. There is something mystically refreshing about anise-flavoured liquors, water and ice. It took a lot of experimentation, however, to come up with a mixture that tames the overpowering anise taste and which integrates this into a less demanding, more enjoyable drinking experience. Here, the sweetness of Maraschino in combination with the freshness of mint leaves seem to do the trick.

But wait, there is more to it. This cocktail's beauty extends beyond the cool look and refreshing taste. There is awesome physical science at work as well. The anise taste in Ouzo is mostly delivered by anethol, a poorly water soluble, organic, oily substance which can, however, be dissolved in alcohol ... unless the water content is too high and the oil again precipitates in the form of small droplets. And this is exactly what happens if Ouzo is mixed with ice and/or water. Light scattering from the droplets then gives rise to our wonderful clouds.

The thermodynamics of such ternary (water-alcohol-oil) mixtures is unique in that they do not require any dispersing agents to form metastable mixtures. The range of water concentrations in which 'clouds' are formed is narrowly confined between the so called binodal and spinodal loci. Flory-Huggins theory, better known for its use in the thermodynamics of polymer solutions, provides some key insights into the mechanism and the role of intermolecular forces that give rise to this unique phenomenon.

If you like, think of the Ouzo effect as a fight between the gods of disorder (entropy) and of (thermodynamic) attraction or love (enthalpy). Clouds are a sign of the raging war between the two being un-decided, with both, disordered and homogeneous f(r)actions competing for dominance. A small change in water or oil concentration will tilt the balance toward totally phase separated or totally homogeneous system.

In this layered cocktail, clouds initially form due to an increase of water content in the Ouzo layer from melting ice. If stirred, dilution by the vodka-curacao- and Maraschino layers will disperse the clouds once again. The cocktail transitions to the stable solubilized phase and becomes clear. Order prevails. Peace arrives. Yeah.

Pour Maraschino into Martini glasses with slightly crushed mint leaves. Add a layer of crushed ice, a layer of the vodka-curacao mixture and finally a layer of Ouzo using a cocktail spoon. Sit down, stir and enjoy. Trust me, sitting is important as you will need to rest on some supporting structure once you have finished this drink.

Zum Wohl, cheers.