n recent decades the Guinness advertising campaign has revolved around the motto that ‘good things come to those who wait’ - a nod to the very precise, elaborate and time-consuming art-form of pouring the perfect pint of the Black Stuff. The brains behind Guinness claim that by following the instructions carefully, you are well on your way to a ‘perfect’ pint of clear, dark stout topped with a white, dense, creamy foam. Do these steps really make any difference, or is it all theatricality? My curiosity got the better of me, so in time for St. Patrick’s Day next week, I thought I would take a closer look at the six steps to the perfect pint of Guinness.
Guinness' advertising campaign based on the recommended settling time of 119.53 seconds (Photo Credit: Guinness)
The two distinctly different layers in Guinness are made of the same substance; the white, foamy head has been whipped up by the escape of bubbles on leaving the keg, leaving the clear dark stout. In my previous article I discussed the interesting flow dynamics of these tiny nitrogen bubbles in a classic Guinness pint glass. As the bubbles are so tiny, they not only create a light mousse-textured head, but the small size and high density of the bubbles contribute to how much light is being scattered by them. In this case, rather a lot, hence the white colour we see. We see the same effect when we agitate Marmite enough with a knife or spoon. As you play with this thick, dark spread, you start to introduce tiny bubbles into it. The more you swirl it about on a plate, the more bubbles become incorporated into the mix, and the lighter the Marmite gets, until it too also looks almost white.
How do we get to this perfect pint though? Bartenders all over the world are presented with the instructions below, breaking the six stages of the pouring process down, including details about the type of glass used, the angle the glass is held at during the different states of pouring, the precise length of time the pint must be left to settle, and the force with which the draught Guinness is poured from the tap. Step 1 is easy - find a Guinness-branded glass. This may be the most important step as the harp logo actually serves as a guideline for many of the following steps. Step 2 says that the glass should be held at a 45 degree angle, and the draught Guinness should be poured by pulling the tap forwards and aiming the flow at the inside of the glass where the harp logo is. By pulling the tap forwards, the Guinness is being poured with some force. As it is forced out of the tap, and on contact with the glass, the bubbles begin to form. By using the maximum force of the tap, the gases in the liquid are agitated and form bubbles, while the 45 degree angle allows small bubbles to form, which give rise to a smoother and creamier head, rather than the larger, glassier bubbles that could form from a more turbulent landing.
Once the bottom of the harp has been reached by the incoming liquid, the bartender must then start to straighten the pint glass to upright by the time the liquid reaches the top of the harp. This takes longer than you think owing to the need to take the glass through the whole 45 degree angle to standing. This is when the real wait happens. The bartender places the still-cloudy not-quite-a-full-pint on the bar and waits for the bubbles to surge down the sides of the glass and up the centre to form the head. This settling step is reputed to take exactly 119.53 seconds. Not two minutes. Not 119 seconds. 119.53 seconds. During this time, any bubbles rise up, creating the two distinct layers which offer more than just aesthetics, which I will come to in a moment.
The final step is to top up the pint, but having gone to all that trouble to form a light head, a high pressure top up would destroy the delicate bubbles. This is why bartenders are told to push the tap away from them in this second stage of pouring, as this halves the force of the flow, filling the glass to the top without destroying too many bubbles. Some bartenders like to trace the shape of a Shamrock leaf into the top of the head as they do this, leaving this lucky charm indented into the foam when it is served, although Guinness themselves do not seem too bothered by this - clearly that is a step too far in terms of detail, even for them.
Pints of Guinness at various stages of their 119.53 second settling period (Photo Credit: Simon Dawson/Bloomberg)
While you may be forgiven for thinking that this science tutorial has come to an end, I am yet to cover the important business of drinking this simple that has probably taken a good four minutes to create. The reason that Guinness are so keen to craft the perfect pint is so that the consumer enjoys drinking it. In order to maximise your chances of this happening, the first sip must be taken horizontally, in order to consume the lighter head with its delicate flavour compounds evaporating off, alongside a gulp of the bittersweet, malty drink; the two together create a perfect balance of flavours in the drink, which Guinness argue you would not experience if a pint was poured without such attention to detail, owing to the creation of larger bubbles, and a head that is either too large or too small.
The key to the perfect look, and therefore taste, of Guinness seems to lie in the role that the bubbles play, but what if you don’t have draught Guinness on tap? Are the bottled and canned versions as good? In my next article I’ll be discussing how scientists and engineers are working with brewers and bartenders to create new and innovative pieces of kit that are bringing the benefits of the bar to homes all over the world.