Traditionally made coffee always appeals to my sense of coffee history. Coffee made its way out of Ethiopea via Turkey and the method of brewing the finely ground coffee in a ‘cezve’ or ‘briki’ is one that goes back a long way. It’s therefore always interesting when a new cafe arrives on the scene that offers “Greek” or “Turkish” coffee on its menu. Briki, in Exmouth Market, opened in May last year and so it was only going to be a matter of time before I visited to try it out. Aesthetically Briki appealed to me as soon as I walked through the door. Spacious and with the bar along one wall, there are plenty of seats available at which to slowly enjoy your coffee. The cafe itself is almost triangular and the other two walls have windows running all along them. What better way to sit and enjoy the moment (and your coffee) than to gaze out a window? Still, given that I had gone to a cafe called ‘Briki’ and that it advertised “Briki coffee” on the menu behind the bar, it was obvious that I had to try the briki coffee. The coffee was rich, flavoursome and distinctive, well worth the time taken to savour it. There was also an impressive selection of food behind the counter and the dreaded “does it contain nuts” question was met with a friendly check of the ‘allergen’ folder. I was therefore able to also enjoy the lovely (nut free) chocolate cake. Briki definitely gets a tick in the “cafes with good nut knowledge” box on my categories list.
© The Trustees of the British Museum
However as I realised later, the coffee was not brewed in the traditional way but in a Beko coffee maker – a coffee maker specifically designed for optimising the brewing of Turkish coffee. The idea of the Beko is that it carefully controls and automates the entire brewing process so that you get a perfect coffee each time. But just how do you make a ‘perfect’ Turkish coffee?
A quick duckduckgo (it’s a mystery to me why has this verb failed to catch on while ‘to google’ is used so frequently) revealed two sets of instructions on how to make Turkish coffee. The first set, (including some otherwise very good coffee brewing websites) suggested ‘boiling’ the coffee repeatedly in the pot (cezve/briki). The second set, which seemed to be more specifically interested in Turkish coffee (as opposed to interested in coffee generally), were much more careful, even to the point of writing, in a very unsubtle way, “NEVER LET IT BOIL“. According to this second set of websites, the coffee in the cezve should be heated until it starts to froth, a process that begins at around 70C, far below the 100C that would be needed to boil it. Warming the cezve to 70C produces these bubbles and the lovely rich taste of the traditionally made coffee. Heating it to boiling point on the other hand destroys the aromatics* that form part of the flavour experience of coffee and therefore makes a terrible cup of coffee.
The contrasting instructions however led me to recall a discussion in Hasok Chang’s Inventing Temperature. Perhaps we all remember from school being taught how thermometers need two fixed points to calibrate the temperature scale and that these two fixed points were the boiling point and the freezing point of water. Perhaps this troubled you at the time: Just as with making coffee in a cezve, just how many bubbles do you need in order to say that the coffee (or water) is ‘boiling’? How were you supposed to define boiling? How much did it matter?
It turns out that these questions were not trivial. There is a thermometer in the science museum (in London) on which two boiling points of water are marked. The thermometer, designed by the instrument maker George Adams the Elder (1709 – 1773) marked a lower boiling point (where water begins to boil) and an upper boiling point (where the water boils vigorously). The two points differed by approximately 4C. So how is it that we now all ‘know’ that water boils at 100C? And what was wrong with Adams’ thermometer? The Royal Society set up a committee to investigate the variability of the reported boiling point of water in 1776. Careful control of the heating conditions and water containers reduced the temperature difference observed between different amounts of boiling. However, as they experimented with very pure water in very clean containers they found that things just became more complicated. Water could be heated to 120C or even higher without ‘boiling’. They had, unintentionally, started investigating the phenomenon that we now know as ‘superheating‘. Superheating occurs when water is heated to a temperature far above its boiling point without actually boiling. What we recognise as boiling is the escape of gas (which is usually a mix of air and water vapour) from the body of the water to its surface. In order to escape like this, these bubbles have to form somehow. Small bubbles of dissolved air pre-existing in the water or micro-cracks in the walls of the container enable the water to evaporate and form steam. These bubbles of gas can then grow and the water ‘boils’. If you were to try to calibrate a thermometer using very pure water in very clean containers, it is highly likely that the water would superheat before it ‘boiled’, there just aren’t the ‘nucleation’ sites in the water to allow boiling to start. The Royal Society’s committee therefore came up with some recommendations on how to calibrate thermometers in conditions that avoided superheating which meant thermometers were subsequently calibrated more accurately and superheating (and improved calibration points) could be investigated more thoroughly.
Perhaps viewed in this way there are even more parallels between Turkish coffee and physics. It has been written that “making Turkish coffee is an art form“. It is a process of practising, questioning and practising again. The Beko coffee machine automates part of the process of making Turkish coffee. When it’s done well though, Turkish coffee is far more than just the temperature control and the mechanics of heating it. There is the process of assembling the ingredients, the time spent enjoying the coffee and the atmosphere created by the cafe in which you drink it. Coffee as art in Briki is something that I would willingly spend much more time contemplating.
Briki is at 67 Exmouth Market, EC1R 4QL
“Inventing Temperature”, by Hasok Chang, Oxford University Press, 2004
*Although these aromatics are part of what gives coffee such a pleasurable taste, they decay very rapidly even in coffee that is left to stand for a while, it is this loss of the aromatics that is part of the reason that microwaving your coffee is a bad idea. A second reason involves the superheating effect, but perhaps more on that another day.