American scientists have studied the process of evaporation and formation of traces of drops 66 whiskey samples at different dilution rates. Due to the shear of the film of the organic components of whiskey on the droplet surface when it is completely dry formed in unique patterns that the authors were compared. The results of a study published in the journal ACS Nano.
How to dry a drop depends on the properties of its components, the nature of non-volatile dissolved substances and particles, and environmental conditions. Understanding the behavior of volatile compounds, it is very important to create new coatings. One of the problems that arise when trying to create a uniform coating is the so — called effect of coffee stains. Due to the capillary effect of the dissolved non-volatile substances when dry are at the edges of the drop. Sometimes it can be useful, for example for the creation of nanostructures, but usually he tried to get rid of.
To suppress this effect, the scientists added in a mixture of various substances to equalize the concentration of nonvolatile components on a surface, including whiskey. The structure of the generated film depends strongly on the composition of the mixture: crushing smooth layer due to intermolecular interactions, the degree of influence depends on the nature of the components of whiskey, can lead to the formation of cavities, forming a unique pattern. Whisky consists mainly soluble in alcohol and amphiphilic, i.e., containing both hydrophilic and hydrophobic areas of molecules. Diluting the beverage with water helps transfer chemicals to the surface of the drop and the formation of nano-sized (30-90 nm) agglomerates.