Researchers have solved a critical piece of the puzzle of how to make strong bubbles in liquids, an advance that may lead to the perfect head of beer -- the frothy foam on top of the alcoholic beverage.
The scientists, including Richard Campbell from The University of Manchester in the US, studied mixtures containing a compound called surfactant which lowers surface tension in liquids.
A new way of understanding these compounds is described in a study, published on Saturday in the journal Chemical Communications, and could help product developers formulate the ideal foam.
As part of the study, the researchers fired beams of neutrons at the liquids used to make foams.
"Just like when we see light reflecting off a shiny object and our brains help us identify it from its appearance, when neutrons reflect up off a liquid they are fired at we can use a computer to reveal crucial information about its surface. The difference is that the information is on a molecular level that we cannot see with our eyes," explained study co-author Campbell.
According to the researchers, while the behaviour of foams made from liquids with only one additive is well understood, knowledge about liquids containing more additives -- like those used in actual products -- have remained elusive.
In these mixtures, they studied the building blocks of the bubbles themselves, known as foam films by reflecting neutrons off their liquid samples.
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Applying this principle, the scientists devised a new way to relate the stability of foam films to the way in which the additives arranged themselves at the surface of the bubbles.
They observed how this process provided the stability needed to prevent the bubbles from bursting.
Campbell said until now researchers had been thinking of general surface properties, and not about the structures created when different molecules assemble at the surface of bubbles.
"It was only through our use of neutrons at a world-leading facility that it was possible to make this advance because only this measurement technique could tell us how the different additives arrange themselves at the liquid surface to provide foam film stability," he said in a press statement.
As a consequence of the findings, the researchers said, beer drinkers in the future may be able to enjoy a pint where the head lasts all the way to the bottom of the glass.
They said the study may also help improve the formulation of detergents used in washing machines where the production of foams is undesirable.
"This is important, as some products benefit from foams that are ultra-stable and others from foams that are very unstable," Campbell explained.