How To Pour The Perfect Pint! | Earth Science

The perfect pour of any beer from a glass or bottle is all about getting the head just right for overall taste and visual satisfaction. Not only does the carbon dioxide in beer head add its own mildly sour taste but the froth itself contains a wide variety of delicate flavours which take the form of tiny molecules that are released and detected in your nose while drinking. Here are five simple steps to getting it just right according to science. I have an average can of lager and I'm going to be aiming for what many would consider a perfectly respectable head of one inch with a slightly domed cap peeking just over the surface of the glass. The most important part of science to consider with any pour is all about carbon dioxide gas and how it can gather together to form bubbles or froth. The scientific term for this is nucleation. The real trick behind the perfect pour is all about controlling the speed at which nucleation occurs. In a carbonated beverage like beer carbon dioxide gas is dissolved in the liquid and forced to stay there under high pressure from the bottle or can. When we open the can or bottle that pressure quickly lowers to the normal pressure around us and some of the carbon dioxide molecules gathered in big enough groups can force back the surrounding liquid and escape in the form of a bubble. This process of degasification is why we observe bubbles forming when we open a bottle of beer or any other fizzy drink for that matter. One thing that helps big enough groups of CO2 molecules to gather together and form bubbles is having hiding places in which to accumulate away from the liquid pushing in from all sides. We call these places nucleation sites and they can be anything from scratches in the liquid's container to the surface of tiny particles in liquid or even other bubbles. Now we've known bubbles we can go on to the important part the scientifically perfect pour. Step one is the big choice you must select your beverage and a nice clean glass. If your glass is dirty and scratched this provides lots of nucleation sites for CO2 bubbles to form and can send your froth out of control. For a very foamy bit you might want to give your glass a quick rinse with cold water as this can effectively mask some of those nucleation sites and reduce the number of bubbles forming and thus you've controlled the head. Step two is the tilt. Hold your glass at a 45 degree angle and gently pour in the beer so there's a small gap between the interior of the glass and the top of your can or bottle. The smooth flow of beer ensures that there's less chance of air getting into the liquid and providing nucleation The 45 degree angle is shallow enough to ensure that beer flows smoothly down the glass without making a big splash at the bottom but steep enough to make sure that there's no up splash when the liquid initially hits the glass. Tilting the glass or can too sharply means that air can enter it as it tries to equalize the pressure inside. This can result in lots more nucleation sites and results in a very frothy brew. Step three, straightening up. When your beer reaches the lip of the glass gently halt pouring and start to straighten. Now a nice headless pour has been achieved we can get ready to intentionally produce that glorious foam. Step four, the long pour. Pour your beer from above into the centre of the glass and watch that creamy head form until it just bows up over the lip of the glass. The long pour incorporates air in with the beer and allows plenty of nucleation sites for co2 bubbles to form. Those bubbles gather together and bring with them lots of stabilizing molecules from inside the beer to form a perfect and relatively long lasting head. Step five, don't lose your head. Whether you like it or not your beer head is contributing many delicate flavours to the overall taste of your beer so instead of sipping take measured mouthfuls to ensure that you don't slurp away all that carefully constructed foam and ruin the steady release of aromas while you drink. Now all beer heads are unstable which means they will gradually disappear as the bubbles burst. In order to maintain them and that steady release of beery aromas many beer manufacturers have included laser etched nucleation sites on the bottom of their glasses which ensures a nice steady release of bubbles throughout your pint experience. Remember that every beer is different so some may need more or less straight and tilted pouring to achieve the desired effect. The important point to remember is that you should enjoy with company and drink as responsibly as possible. Cheers!