NPL

Carbon Kopi

Carbon Kopi, coffee Hammersmith, coffee Fulham
Carbon Kopi, the sign in the window above giving a clue to the name without being a direct reference.

The name of this relatively new cafe in Hammersmith/Fulham was intriguing on several levels. Kopi means coffee in both Malay and Indonesian and, having recently travelled back from SE Asia, it was interesting to see what the link to this cafe may be. Then there was the pun in the name. The website explains it as representative of a desire to make a consistently good coffee, each being a carbon copy of the other. So both the name, and the cafe’s symbol have appeals for a coffee-science website. And so it was that we wandered down Fulham Palace Road to finally arrive at Carbon Kopi a few Saturdays ago.

The cafe occupies a corner building and is much larger than you may expect it to be. It is also friendly, airy and light with large windows giving plenty of illumination to the space. Allergen information was clearly labelled on the cakes and edibles (with extra information in a folder), which is always great to see.

Coffee was by Square Mile with guest roasters on batch brew and so we had a long black and oat milk hot chocolate which came served in huskee cups. Huskee cups are produced by re-using the husks otherwise discarded during the coffee milling stage. A re-usable cup that reduces waste certainly, but does it reduce the carbon footprint? An answer that depends on how many times you use it. Continuing the environmental theme, near the door, there was a separate bin for compostable cups. This was excellent to see because if compostable cups do not get to an industrial composting facility, they can take an absolute age to break down in a conventional compost heap.

Hat and huskee
Coffee in a huskee cup at Carbon Kopi. A protrusion on the saucer fits into the base of the huskee cup and stops it slipping across the saucer. Unlike graphite where the regular hexagons of carbon form layers that slip over each other to form a solid lubricant.

Across the road, the St Alban’s Church was made of brick. One row upon another, the set of bricks formed a layered structure. Where they met at corners or against the pavement they formed abrupt discontinuities, a sort of dislocation. Together with the small protrusion on the middle of the huskee cup saucer (to stop the cup slipping?), and the speaker above the door entertaining us with 80s music, the natural connection here was graphene.

Graphene is a form of carbon that is a single atomic layer thick. Each carbon atom is arranged into a flat hexagonal structure exactly like graphite but, unlike graphite, there is only one layer of these atoms in graphene. The strength and strange electrical properties of this material, together with its lightweight form, have made this material an intense subject of research for the past 15 years or so. A recent Physics World podcast tested a set of headphones with the vibrating membrane made of graphene. The idea being that the strength of the material combined with its relatively low mass, would enhance the way that we heard the sound coming through the speakers. You can listen to the review (though not the speakers) here.

coffee Hammersmith
Each layer of bricks forms a regular set of layers. But where they come up against each other discontinuities are formed. These can cause special problems in sheets of graphene.

But are there aspects of graphene that may be more applicable to the cafe and coffee industry? Various teams around the world have been working to make membranes of graphene work as single molecule detectors. The idea is that molecules adsorbed onto the surface of a graphene membrane change the electrical properties of the membrane to an extent that can be measured even in the case of single molecule adsorption. The sensitivity of the electrical properties of the graphene to different molecules could mean that graphene based devices would make very sensitive contamination detectors, including allergen detectors. Such sensors are the subject of a research collaboration at the National Physical Laboratory in Teddington and could mean that, rather than be in any doubt as to whether a substance contains an allergen, it could be quickly tested by passing it through a graphene sensor.

All this is quite far from the coffee and cakes at Carbon Kopi. But if you are in the area, it is a lovely place to stop, enjoy a coffee and contemplate the bricks of the church opposite.

Carbon Kopi is at 11 Margravine Road, W6 8LS

Metrology and the Press Room, Twickenham

Press Room coffee Twickenham

The arrival of the pour over at the Press Room, Twickenham.

It is not often that I have an errand to run in Twickenham, but when one popped up just two weeks after reading Brian’s Coffee Spot review of The Press Room, it was obvious where we were going to have a coffee. The Press Room serves pour over coffees (along with a good selection of other drinks). It is always great to find somewhere that serves pour overs well and so I had no hesitation in ordering a Nicaraguan “Los Altos” prepared by V60. Hot chocolate was available as white, milk or dark chocolate and there were a number of alternative non-dairy milks on offer as well as a large variety of tea. A lovely feature of The Press Room is that they offer suspended coffees, the idea being that you buy a coffee now for someone later who may not otherwise be able to afford one. The total number of coffees (given/claimed) is recorded on a blackboard behind the counter. It was nice to see that at the time of our visit 800+ coffees had been paid forward (and just less than 800 claimed), suggesting that the Press Room is having a positive effect on its local community.

clock wall Twickenham coffee

The large clock on the wall at The Press Room in Twickenham.

A great thing about ordering a pour over is watching as the barista expertly prepares your coffee, taking the time to do this properly. To be fair, this is part of the reason that finding a café serving pour-overs is becoming more difficult. After a while, the coffee was brought over to our table together with a bowl ready for me to place the filter cone on it when I was ready to enjoy the coffee. After taking the obligatory photograph, and pondering when would be the best time to remove the filter from the top of the mug and place it onto the empty bowl, the clock next to us took our attention. It is a large time piece that dominates this corner of the room. It is revealing to consider how the accuracy and availability of clocks have changed the way we live as a society.

Considering measurement (of time and other things), I used to be in this area more frequently a few years ago when I worked on a project in collaboration with the National Physical Laboratory (which is down the road, on the same bus route that Brian’s Coffee Spot notes takes you to a few good cafés). Partly, NPL’s work is to ensure that we know how to measure things properly. Take the pour over I enjoyed at The Press Room. A known amount (perhaps 12 g) of coffee was weighed out before 200 g of water was poured slowly over the coffee. But how do you know that the 12 g measured at Press Coffee is the same 12 g as you measure at home? And while perhaps it may not be critical for the coffee culture (even the most extreme home-brewer does not need to know the amount of coffee they are using to the nearest 0.000 002%), knowing accurately how heavy something is can be extremely important. Hence the need for a standard kilogram (and a standard metre, second, Candela etc) so that we have a way of knowing that what you call a kg is the same as what I call a kg.

coffee bowl pour over

The coffee that escaped! But was it a measure of my patience or hesitation?

Oddly, the kilogram is the last fundamental unit still defined with reference to a physical object (the other fundamental units are seconds, metres, Kelvin, Amperes, Moles, Candelas). The kilogram reference block is a PtIr alloy kept at the International Bureau of Weights and Measures near Paris. However all this may change next year depending on a decision due in November 2018. If all goes to plan, from May 2019 all units will be defined with respect to natural constants such as the speed of light etc. For the kilogram, this has meant measuring mass relative to a magnetic force generated by a coil of wire in a device known as a Kibble balance. In this way, the kg can be defined with respect to Planck’s constant and an era in which we measured substances relative to known objects will end.

On a day to day level though, how much do these things matter to us? Sometimes the way we measure things affects how we view them (and therefore what questions we ask next). Take for example temperature. We are used to measuring degrees of ‘hot’, so on the centigrade scale 0ºC is the freezing point of water and 100ºC is the boiling point. But it wasn’t always this way. Celsius devised his original scale to measure degrees of cold so 0º was the boiling point of water and 100º was the freezing point (you can read more about that story here). It is arguable that changing to measuring degrees of ‘hot’ enabled us to more easily conceptualise the idea of heat as energy and the field of thermodynamics. Certainly for a while, considering the idea of ‘degrees of cold’ meant that some looked for a substance of ‘cold’ called “frigorific“¹. There’s a similarity here with the coffee at The Press Room, was the amount of coffee in the bowl used to hold the filter after I removed it from the mug a measure of my impatience before trying the coffee or my hesitation at testing the coffee? How we ask that question affects how we view the coffee and the café (for reference, I would take the positive interpretation: the amount of coffee in the bowl measures my impatience; I was eager to try the coffee).

droplets on the side of a mug

Condensation on the side of the mug. These droplets can reveal many aspects of physics, which do you think about?

Partly this suggests some of the ways in which language, and philosophy, underpin all science. It certainly suggests one further connection with this bright and comfortable café. Erich Fromm in “To have or to be”² considered an interesting linguistic usage that reveals our way of being. Do we “have an idea”, or do we “think”? Are we consumers or people with experiences? Do we wish to have, to acquire, to consume or do we wish to exist, to be. Our language affects how we perceive the world which in turn changes the language we use about it. Linguistically, depending on how we interpret the cafe’s name “The Press Room”, we either have a café that offers a space to read the latest news or one that is reflective of the coffee brewing process (specifically espresso); a space to get up to date or one in which to contemplate? The symbol of the café visible in the frontage of the shop and on the mugs suggests the latter, but maybe it is something we need to experience to truly know?

¹Inventing Temperature, Hasok Chang, Oxford University Press, 2008

²To have or to be, Erich Fromm, Jonathan Cape, 1978

The Press Room is at 29 London Road, TW1 3SW

Setting the standard for coffee brewing

Chemex, 30g, coffee

A Chemex, how much coffee do you need to make a good cup (or two?)

Serious coffee drinking requires a serious attention to preparation. Various online guides (such as this one from Ineedcoffee.com) specify the ratio of water to coffee that you need and some will dictate the exact quantity of coffee that you should grind ready for your brew (30g for a standard, 500ml Chemex). Different brew methods require different amounts of coffee. Some will insist that the correct ratio of coffee to water is essential for a good coffee. So how can we ensure that 30g of coffee is really 30g? How do I know that what you measure as 30g is what I measure as 30g? It is a question that reveals a fascinating answer. The measurement of mass, the definition of the kilogram, is the only unit of measurement left for which we still use a physical standard as the reference.

This means that there is a physical lump of metal (it is actually a platinum-iridium alloy) that is sitting in a lab somewhere (Paris) against which all our definitions of mass are referenced. If you were to weigh out 1 Kg of coffee, your scales would, ultimately, be referencing this 1Kg lump of platinum-iridium in Paris. My scales reference the same standard and so we can be sure that, assuming our scales are accurate, your 30g is equivalent to my 30g. Many years ago (in 1884), forty replicas of this standard of measurement were made and distributed throughout the world. The idea was that rather than have to always refer to the Parisian standard, there would be a more local ‘standard’ that people could refer to. The problem of course is that the standards diverge, they have to be regularly re-calibrated so that the Kg in Paris weighs the same as the Kg in London (well, just outside London in Teddington, at the National Physical Laboratory).

gold weights, standard weights, not Kg

A set of gold weights from China in the British Museum collection. © Trustees of the British Museum

The reason appears to be because the standards get dirty. The surface of the metal adsorbs contaminants from the air which make the standard seem heavier. Admittedly, this may not be by much, only perhaps tens of μg, but over many tonnes, this small difference is going to add up. And if you trade in commodities (such as coffee beans) and are paying by weight of coffee then such differences, in large amounts, may be costly. So what is the solution? One method involves finding new ways to clean the standards so that they are contamination free. A more long term solution is to move away from measuring relative to a physical standard at all. After all, length is no longer measured with reference to a stick in a lab but with reference to the distance that light travels in a certain amount of time. Research is now being done into exactly this in metrology labs around the world. At some point in the not to distant future, it is very likely that the Kg will be defined with reference to an electrical measurement, for example, rather than with reference to a physical block of metal. For the meanwhile, we have to hope that the standards labs around the world keep their blocks of metal very clean otherwise, how would we ever expect to get the correct amount of coffee in our Chemex?

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