By Stephen Beech

What makes the frothy head on a pint of beer so stable has finally been worked out.

And the findings could help develop new firefighting chemicals and to treat varicose veins, as well as enabling anyone to pour a perfect pint every time, say scientists.

A big head of foam at the top of a poured glass is often seen as one of the clearest signs of a good ale.

Even brewers will use the quality of froth as an indicator of a beer having completed the fermentation process.

However, despite its importance, what makes a large, stable foam head was not entirely understood until now.

Researchers have discovered that, for single fermentation beers, foams are held together primarily through the surface viscosity of the beer .

However, for double-fermented beers, the protein

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