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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

(Im)perfect reflections on coffee

science in a V60

Have you noticed droplets like these dancing on your drip-brewed coffee?

With the recent coffees from Hundred House and Quarter Horse, there have been many opportunities to observe the coffee brewing in the V60 in the mornings. The steam rising from the filter paper, the different ways different coffees bloom and out-gas, the droplets that skim the surface of the coffee and bounce off the walls of the jug and then, of course, the many different effects with light. Watching the dancing droplets (an explanation of why they may dance is here), it is perhaps not immediately obvious that you could form a connection between these, the light reflections and an insight into something you may have noticed while passing through customs. And yet the connection is definitely there.

The connection is formed through a technique called Raman spectroscopy. Named after Chandrasekhara Venkata Raman (1888-1970) who discovered the Raman effect in 1928. As the ‘spectroscopy’ part of the name suggests, it is a technique that offers a way to identify different chemicals, or components, in a substance. For coffee it has been used both as a non-destructive technique to determine the kahweol content of coffee beans and hence help as a test for identifying rogue robusta in arabica beans and as a way of analysing the brewed coffee. But what is it, how does watching a brewing V60 help to understand it and why would you want to know about Raman spectroscopy while travelling through an airport?

beauty in a coffee, coffee beauty

A collection of bubbles on the side of the coffee. What happens when one of the dancing droplets collides with a group of bubbles?

Generally, it helps to begin with coffee and the link is the way in which the droplets bounce off the side of the jug. Brew a coffee and watch them (if you are a non-coffee drinker, you could try dripping hot water through a filter paper into a jug). When one of these droplets hits the wall of the V60 container, it generally bounces back with a trajectory expected for an elastic collision. Given the relative masses of the droplet and the jug, the speed of the reflected droplet is essentially unchanged (even if its direction is reversed). This is similar to what we would normally expect for light. We are used to considering light as waves but because of the wave-particle duality of quantum mechanics it is equally valid to consider light as a stream of particles called photons. As the photons hit a surface and are reflected off, they recoil with the same energy that they initially had, just like the droplets in the coffee. But now look more closely at the dancing droplets. Normally they hit the walls and not each other but just occasionally, they can hit either another droplet or a group of bubbles that have formed on the coffee surface. In these cases, rather than get reflected as before, the droplets transfer some of their energy to the collection of bubbles causing them to move and to wobble. And when the droplet is reflected back, it has a noticeably slower speed (and so we could say a lower kinetic energy) than when it initially danced into its collision. Where is the analogue with light?

When we think about a coffee bean, we probably think about something that is about 1cm oval, brown and quite solid. But if we zoom in, we find that it is made up of a collection of atoms bound together in molecules or, if we are thinking about a solid like salt, in a crystal structure. These atoms act as if they are balls connected by springs and so they wobble as would any structure of masses connected by springs. This is true whether the crystal is diamond or the molecule is caffeine, kahweol, cocaine or semtex (do you see where the customs part is going to come in yet?). Different crystal structures have different atomic arrangements meaning that they are effectively connected by springs of differing strength. If you build a mental model of masses connected with springs, you can see that changing the spring strength will change the vibration energy of the structure. So if now we think about the photons hitting such a structure, while most will bounce off as we saw with the droplet hitting the V60 wall, some photons will trigger a wobble in the crystal structure and bounce off with lower energy. It is a process analogous to the droplet hitting and bouncing off the collection of bubbles on the coffee surface.

Sun-dog, Sun dog

Sun dogs are caused by a different interaction between light and crystals. Rather than the inelastic scattering of Raman spectroscopy, Sun dogs are caused by the refraction of light by hexagonal platelets of ice crystals.

When a photon of light loses energy, it is equivalent to saying that the frequency of the light has changed (which is very closely related to what Albert Einstein got his Nobel prize for in 1921). So a photon that creates a crystal vibration and is scattered off with lower energy has a lower frequency (or longer wavelength) than it had when it first hit the crystal. Importantly, the energy lost by the photon is identical to the energy gained by the vibrating crystal and so by measuring the frequency change of the scattered light we have a way of determining the energy of the crystal (or molecule) vibration. As this energy depends on the way that the atoms are arranged in the crystal or molecule, measuring the frequency shift offers us a way of identifying the chemical under the laser light: kahweol or cocaine.

It is not an easy technique as you can guess from the V60 analogy. Only around one in a million photons incident on a solid will be Raman scattered. You need some pretty decent optics to detect it. Nonetheless, it is a powerful technique because no two chemical structures are the same and so it can be used to identify tiny amounts of smuggled material completely non-destructively. It becomes easier to understand how this elegant technique has become useful for many areas of our lives from customs, through to pharmaceutical development and even into understanding how fuel cells work.

Although it is stretching the analogy too far to say that you can see Raman scattering by watching the droplets on your V60, it is certainly fair to say that watching them allows you the space to think about what is happening on a more microscopic level as your bag is hand-scanned at customs. What do you see when you look closely at your brewing coffee?

 

As quick as (a) Quarter Horse

Dog and Hat, Dog & Hat, Hundred House, Quarterhouse coffee

The package from Dog & Hat with Hundred House and Quarter Horse. Is it a particularly contemplative dog with the monocle?

Links with science can be found everywhere, from the café to the coffee roaster. A couple of weeks ago a delivery from Dog and Hat coffee gave me an opportunity to explore the random thought paths that may occur if you stop to ponder your coffee at home rather than in a café. The first coffee, an Ethiopian from Hundred House prompted thoughts on star gazing. But the second coffee, a Mexican from Quarter Horse coffee was equally thought provoking.

Finding time to prepare a V60 and sit with the SCAA “flavor wheel” as a guide, I was rewarded with a sweet, well rounded and perfectly enjoyable brew. I found fruity notes of blueberry and cherry/pineapple though the tasting notes on the packaging say “green grape, toffee and cocoa”. Sadly I missed the cocoa but this offers a good excuse for another slow brew with the coffee wheel at hand.

Thinking about the name of the coffee, I started to consider how you could quarter a horse. Perhaps not a literal horse given the ethical considerations but rather an irregularly shaped volume. How would you divide, into equal portions, an irregularly shaped object such as a horse? It seemed related to the question of finding the shortest route between two locations, how would you calculate the best route to take from A to B? In the 1950s a computer scientist called Edsger Dijkstra (1930-2002) came up with an algorithm to calculate precisely this problem. Originally designed to show the shortest routes between 64 cities in the Netherlands, Dijkstra’s algorithm is now ubiquitous in our lives.

Quarter Horse but how would you

A close up of the Quarter Horse Coffee Bag.

One of the ways in which we have started to rely on such algorithms is in car GPS devices or even on our phones trying to navigate to our destinations. Or at least, many of us do. London taxi drivers however have been shown to have developed a different brain structure from the general population that means that, for them, Dijkstra’s algorithm may be unnecessary. A few years ago, a study compared brain scans of people who had been driving London’s “black cabs” for a number of years to those of us in the general population. A follow-up study followed three sets of people over several years. A control group of people in the general population and a second group of people who studied the “Knowledge”, the navigational test that London taxi drivers have to pass in order to become cabbies. The Knowledge tests the driver’s ability to recall tens of thousands of London’s streets and the prospective cabbie can be asked to navigate between two points anywhere within a 6 mile radius of Charing Cross. Typically it takes years to acquire the Knowledge and not everyone who starts on the Knowledge will pass (the pass rate is only about 50%). This means that this second group of people splits into two groups; those who studied and passed the Knowledge and those who studied but did not pass.

The studies proved illuminating. One particular part of the brain, the posterior hippocampus had a greater volume of “grey matter” (the brain processing cells) in taxi drivers who had studied, and passed, the Knowledge compared with the general population. Moreover, those that had been taxi drivers for longer, showed larger posterior hippocampi. The changes in the brain seemed to lead to the cabbies having not only better navigational ability than the general population but better memory for London based information. The study of the trainees moreover confirmed that these brain changes occurred as a result of learning the Knowledge, showing that our brains are adaptable and still able to develop well into adulthood. While the brains of all the study participants started off similarly, those that went on to pass the Knowledge had a larger posterior hippocampus than those who either didn’t study or studied but hadn’t passed. However it was not all good news for the cabbies. The growth of the posterior hippocampus seemed to occur at the expense of the anterior hippocampus in long serving taxi drivers (but not newly qualified ones). The improved memory for London based information shown by the taxi driving group was also accompanied by a poorer ability to learn other visual information/memory related tasks in those that passed the Knowledge compared to the general population.

taxi and motorcycle, London

London black cab drivers have been shown to have a larger volume of grey matter in the posterior hippocampus area of their brains, demonstrating that our brains remain adaptable well into adulthood.

Perhaps the ability of the cabbies to navigate quickly around London’s streets suggests a second connection with Quarter Horse. A Quarter Horse is a breed of horse that can sprint very quickly over short (less than a quarter of a mile) distances. Which goes faster, the cabbie with the Knowledge or us with our smartphones once we have plugged in our destination? We are reminded of the tale of the hare and the tortoise. But I think a different tale is more appropriate. A tale that in reality was only ever a snippet of an ancient saying but has been developed into tales by thinkers such as Isaiah Berlin and Ronald Dworkin.

“The fox knows many things but the hedgehog one important thing”.

What does this mean? It seems there is a connection here between coffee roasting and taxi drivers, between algorithms and personal development, between coffee science and writing about coffee science. Is this connection really there or is it a meaningless statement that leads us into blind alleys of coffee consideration? It may be time to stretch our brains, grow our grey matter a bit and contemplate. Am I a fox or a hedgehog and where do London cabbies and coffee roasters fit in?

Quarter Horse coffee is online at https://quarterhorsecoffee.com

You can find out more about the coffee subscription site Dog and Hat on their website https://dogandhat.co.uk

You can read more about the taxi driver study on the Wellcome Trust’s press release about it here.

Enjoy your coffee, have fun thinking, grow your grey matter.

 

 

A shocking coffee connection

There have been some fantastic thunderstorms in London lately. Perhaps nothing to rival thunderstorms in the tropics but for this region of the world they were quite impressive. One lightning storm in particular came very close. Thank goodness for lightning conductors! Perhaps the connection between lightning storms and coffee is not obvious. But maybe this is because you mop up your coffee spillages too quickly.

Reynolds, rain, waves, pond, raining

There are so many coffee-physics connections with rain and weather. It’s worth looking out for more.

The link is in the mess and the maths. It turns out that the maths describing water evaporating out of a drying coffee droplet is the same, in one crucial detail, as the maths describing the electric fields around a lightning conductor. If we want to see why this may be, we need to get a little bit messy and spill some coffee.

The question is how do coffee rings form? We know that to start with the solids in the coffee are distributed fairly evenly throughout the drink. It is the same when you spill it, initially a spilled drop of coffee looks like, well, coffee. But if you wait as this spilled coffee dries, you will find that a ring starts to form around the edge of the drop. How? How does a uniform coffee distribution when the drop is first spilled become a ring of coffee solids around the edge of the dried drop?

coffee ring, ink jet printing, organic electronics

Why does it form a ring?

A number of different aspects of physics feed into this problem but the one that is relevant to the lightning conductors concerns how the water in the drop evaporates. If you think about how a water molecule escapes (evaporates from) the droplet, it is not going to go shooting off like a rocket blasted out from the drop. Instead it will take a step out the drop then encounter a molecule in the air and get deflected to a slightly different path and again, and again, and so on. It follows the same sort of “random walk” that we know that the bits of dust on a coffee surface follow (and the same sort of random walk that provides a link between coffee and the movements of the financial stock exchange but that is a whole other topic).

Now think about the shape of that spilled coffee drop. If a water molecule were to evaporate from the top of the dome of the drop, it has a certain probability of escaping but it also, because its path is random, has a certain probability of re-entering the droplet. A water molecule at the edge of the droplet however will have a lower probability of re-entering the droplet purely on the basis that there isn’t so much of the droplet around it. Over many molecules and many ‘escape attempts’, this lower probability of re-absorption will translate to a higher flux of water molecules evaporating from the droplet at the edges. The water will evaporate ‘more quickly’ from the edge of the droplet than from the top of it.

artemisdraws, evaporating droplet

As the water molecules leave the droplet, they are more likely to escape if they are at the edge than if they are at the top. Image © @artemisworks

When this is written mathematically, the rate of evaporating water is related to the contact angle between the drop and the surface. The shallower the angle, the higher the rate of evaporation or equivalently, the greater the ‘flux’. It is this mathematical expression that is the same as for the lightning conductor if, rather than refer to an evaporating water flux we refer to an electric field. So the more pointy the conductor, the greater the field concentration around it. A shocking example of the idea that everything is connected.

Of course, there is much more to the coffee ring than this with physics that relates coffee rings to bacterial colonies, burning cigarette papers and soap boats. If you are interested, you can read more about how coffee rings form (including why a higher evaporation rate helps lead to a coffee ring effect) here. If on the other hand you want some well justified thinking time, go spill some coffee and watch as the coffee dries.

Hundred House: Wonder what they are?

Dog and Hat, Dog & Hat, Hundred House, Quarterhouse coffee

Look what arrived! The package from Dog & Hat with the distinguished logo.

What would happen if, rather than five minutes taken noticing the surroundings of a café, you were to look closely at the coffee you brewed in the morning? Different roasters, different coffees, an opportunity to notice something new in each brew. And so it was that a couple of weeks ago a package arrived in the post from the coffee subscription site “Dog and Hat“. Together with a note (in answer to a question I had sent them) ‘Recycled box, paper, mail bag’, came two coffees. An Ethiopian honey processed coffee from Hundred House and a Mexican washed coffee from Coatepec via Quarter Horse coffee.

Each time I moved the bag from Hundred House, a lovely aroma was released. So I moved it around quite a lot. While brewing a V60 with it, the morning light poured through the window producing beautiful lensing effects through the bubbles on the coffee surface and reflections from the coffee itself. The brewed coffee had such a sweet, fruity aroma reminding me of cherries that gave way to plums on tasting. What I took as toffee seemed to be described on the tasting notes as “dates” or “molasses”. Close enough I think. A lovely coffee to enjoy slowly.

Hundred House coffee

The Hundred House coffee bag. With that aroma, indeed how I wonder what you are.

Printed onto the bag was a star with extra lines coming out of it, suggestive of a twinkling star at night. Although each star is massive, they are all at such a great distance from us that they appear to us as point sources of light. And since all light gets refracted when it goes from one medium to another (think about the appearance of that paper straw in a glass of water) the star will appear to twinkle from our position on the Earth below our turbulent atmosphere. Although on a clear night we may not notice it directly, regions of relative hot and cool air in the atmosphere are constantly moving. Layers of air move over each other creating waves much like you see on the seashore and it is this turbulent environment that refracts the light from the stars in such a shimmering way. We can see a similar effect in tea (though not so easily in coffee*): When we pour hot tea into a cold cup, the convection in the cup leads to there being areas of hotter and cooler tea. The refractive index of water is temperature dependent and so the light incident on the tea gets refracted (bent) by different amounts depending on whether it encounters a cool region or a warm region. This leads to the lines of light that we see dancing on the bottom of the cup¹.

KH instability, Kelvin Helmholtz instability

Not a great example of a Kelvin Helmholtz instability but it gives the general idea. This one was quickly snapped from a moving car, I’m on the lookout for a better example.

Although atmospheric turbulence is inferred by the twinkling of stars, a beautiful visualisation of that turbulence can be seen in the form of the Kelvin-Helmholtz instability. Named after Lord Kelvin and Hermann von Helmholtz, this instability manifests as a string of waves on a cloud. It occurs when a fast moving layer of air flows over a slower moving one. The phenomenon is fleeting. If you are lucky enough to see it, the pattern manifests only for a very short time. They are definitely worth watching out for.

Depictions of atmospheric turbulence can also be seen in some paintings. It is said that Vincent van Gogh’s depiction of turbulence in his painting “Starry Night” is extraordinarily accurate. Certainly it is striking that the turbulence depicted by van Gogh does look like the turbulence in a coffee cup. However apparently it goes much deeper than this. In a numerical analysis of the turbulent patterns in a few van Gogh paintings, researchers showed that van Gogh’s depiction was very close to the mathematical (Kolmogorov) description of turbulent flow.

Coffee, Van Gogh

Van Gogh in a coffee cup. Reminiscent of his painting “Starry Night”, there are remarkable mathematical similarities between what van Gogh depicted and real turbulent events.

On their website, Hundred House discuss their aim of being a “collective space, where conversation, art and industry meet, over a cup of coffee”. Pouring a coffee, and watching the turbulence in the cup, perhaps pause a while to consider these points of connection and maybe add a bit of science to the mix. This week if you are in the Northern hemisphere, the Perseid meteor shower offers a particularly great time to reflect on turbulence in the atmosphere and the twinkling of the stars. If you locate the “W” of Cassiopeia (currently in the north east viewed from London) and watch, slightly underneath it towards Perseus, you should see a few meteors of the Perseid meteor shower (perhaps 60-70 per hour during the peak of 11th-13th August). While watching for the shooting stars, it is worth looking at those that twinkle. Which twinkle more, the stars of Cassiopeia or the stars toward the horizon? Why do you think this is?

Whether you watch the stars or just prepare your coffee, take the time. Enjoy your brew.

You can find out more about the coffee subscriptions at Dog and Hat coffee, here and more about Hundred House coffee, here. Do get in touch (email, Twitter, Facebook or comments) if you notice anything you want to share.

 

*We don’t see this so often in coffee because coffee, generally, absorbs more light than tea and so it is harder to see the bottom of the cup.

¹Another effect that can lead to these patterns in swimming pools and similar large bodies of water is caused by waves on the surface of the water. Where waves form on the surface of the pool, the curved surface acts as a lens focussing the light to the floor of the pond. As the waves move on the surface, the pattern on the pool floor will change similarly to that in the tea cup.

Time out

Perhaps an unusual post but there is so much opportunity to stop, think and notice at the moment. Whether it is relaxing in a café with a cold brew or sipping a take-away in a park. There is time to slow down and ponder. Here are three points that have been puzzling recently. What do you think? Perhaps you have other things that you ponder while sitting in a café? Let me know either in the comments section below, on twitter or on Facebook.

oat milk, kone, filtering

Oat milk filtering through the Kone filter – but what does oat milk tell us about Brownian motion, molecular ‘reality’ and the nature of a scientific theory?

Molecules, the atmosphere and oat milk.

On pouring home-made oat milk into a cup of black tea, it is noticeable that a large part of the oat milk is dense and falls to the bottom of the cup (before being stirred by the turbulence in the tea). A similar phenomenon is found in the rarefaction of gases through the height of the atmosphere and in the distribution of dye in water paint. This latter effect was used to establish the existence of molecules back in 1910. The idea that Brownian motion was caused by molecules had been problematic because there was no way to see molecules in a liquid producing the Brownian motion. The theory linking the two was only developed properly in the early twentieth century. What makes a scientific theory? Is it legitimate to postulate something that cannot currently be observed experimentally?

Packing value

Why does roasted coffee often come in plastic packaging that is unrecyclable and not very reusable? What could prompt a move to a more circular economy. Would it be possible to recycle plastic bottles into coffee ‘boxes’ with an air valve at the bottle top (see pictures). This would increase the recyclability without seeming to affect the taste of the coffee?

bottle, coffee bottle, coffee box, coffee packaging

An idea for a circular economy suitable coffee packaging? Recycled plastic bottles as airtight coffee containers.

Related to that, what are your coffee values? Do you favour taste and aroma, traceability, sustainability? Does the packaging that your coffee arrives in feature? Which of these is more important to you? Does the way you drink coffee reflect this?

Footfall past a café

How many people are walking past the café you are sitting in each minute? How many does that translate to per day (accounting for differences in day/night footfall)? Assuming the paving stones remain the same, how long would it be until the successive footprints of all these people caused erosion of the pavement surface? What are the implications of this for the geological features near you?

Whatever you think about in a café or while drinking a coffee, enjoy your time taken out to think. Perhaps you will notice something (or realise something) very interesting or noteworthy and if you have any thoughts on any of the above do let me know either in the comments, on Twitter or on Facebook.

 

Bee-ing positive at the Sugar Pot, Kennington

coffee and cake Kennington

Banana bread and coffee with a sugar pot in the background at Sugar Pot, Kennington

What is it that makes a great café? A space to slow down and think? Good coffee and cakes? A local business that forms part of its local community and gives back to that community in different ways? As I was looking around for a new café to try, I was reminded of Sugar Pot in Kennington. Their website suggested that it ticked all of these boxes and so I was eager to try it (so eager in fact that I didn’t note the opening times, they close at 3 on week-days which is a problem when you arrive at about 2.55). So a second attempt at trying Sugar Pot was arranged, this time safely before lunch. This time, in the morning, there were quite a few chairs and tables outside the café in a roped off area of the street. (We hadn’t noticed this on the first occasion we visited as they had all been piled up inside the shop by the time we arrived). Most of these tables were occupied indicating that it is clearly an attractive place for locals to meet and chat over coffee. Fortunately there were also a fair number of tables inside which suited us as a café often offers more to ponder inside than out (though outside offers a different perspective particularly for people watching).

Inside, each table has an individual character and one in particular offered several points to think about both in terms of physics and aesthetics (you will have to visit to understand). However, it was elsewhere that my attention was drawn that day. Coffee is roasted locally by Cable Bakery while the cakes are from John the Baker of the Kennington Bakery. Sugar Pot definitely gets a tick in the “allergy friendly” box because they answered confidently (and with required caveats about traces) my dreaded question “does it contain nuts?” So I was able to enjoy a lovely slice of banana bread with my coffee. Most of the usual espresso based drinks are available (but not listed on the menu) together with a French Press coffee for those who prefer a non-espresso brew.

Interior Sugar Pot, Kennington

Noticeboard, magazines and coffee counter at Sugar Pot in Kennington

The community feel of the café was immediately apparent with a notice board adjacent to the counter being packed with notices of different activities happening around the locality and within Kennington Park which is just opposite. Underneath the counter were books and magazines and an advert for volunteering with the local bee keeping and urban farming organisation Bee Urban. This is indeed another way that Sugar pot gets involved in its local community. The coffee grounds are donated to Bee Urban for use in their Kennington Park based composting facility. Bees of course have an Albert Einstein link with physics as he is alleged to have said

“If the bee disappeared off the surface of the globe, then man would have only four years of life left. No more bees, no more pollinators, no more plants, no more animals, no more man.”

I do not know if he really did say this but it is a sad reflection on our society that rather than address our environmental crimes we are researching pollinating with drones. However, it turns out the the bee has a much more exciting, almost shocking, link with physics and one that I only discovered thanks to the excellent book “Storm in a Teacup” by Helen Czerski¹. The bee is indeed a very positive creature.

ultra violet, bee, bumble bee

The world looks very different to a bee. Image © www.gardensafari.net

Whether or not they have a happy disposition, it seems that 94% of bees are, electrically speaking, positively charged². They pick up a static charge while flying through the air in a similar way to a balloon being rubbed on your hair. Flowers meanwhile have a negative charge meaning that in addition to colour, shape, scent and pattern, bees can recognise flowers by their electric fields. These fields in turn mean that pollen from the flower ‘jumps off’ and adheres to the bees fur before the bee has even landed, increasing the efficiency of the bee as a pollinator. But it turns out that there is much more to it. When the positive bee lands on the negative flower, there is a charge transfer that results in a change of the electric field around the flower for a duration of 100 seconds or so. By constructing artificial flowers held at different voltages containing either a sugar reward or a bitter centre, researchers at Bristol university found that bees could learn to recognise which ‘flowers’ contained the sugar and which were too bitter to be visited by sensing the electric field around the ‘flower’. It suggests that the changing electric field of real flowers provides a mechanism by which the bee can recognise if a flower has been recently visited by another bee and so been recently pollenated. This would mean that by ‘feeling’ the electric field of the flower, the bee may decide that it would be more rewarding to carry on to a differently charged flower. You can read more about the research in the paper here.

It seems to me that learning about how the bee senses its environment reveals even more about the amazing way that nature (and physics) works. And this offers a link back to Sugar Pot. On the shelf behind the counter back at Sugar Pot was a card that had the message “Keep safe, live to be”. What does it mean “live to be”? In the environmental encyclical Laudato Si’, Pope Francis urges everyone to slow down and notice things such as the bee commenting that “If someone has not learned to stop and admire something beautiful, we should not be surprised if he or she treats everything as an object to be used and abused without scruple.” He goes on “… when media and the digital world become omnipresent, their influence can stop people from learning how to live wisely, to think deeply and to love generously… True wisdom, as the fruit of self-examination, dialogue and generous encounter between persons, is not acquired by a mere accumulation of data...”³ Which is one reason that in order to be, we may want to come back and take a closer look at those bees. Taking time to experience our coffee in a relaxing space such as Sugar Pot and to watch and ponder as the bee uses senses of which we are barely aware can never be a waste of our time. Indeed, it is possible that our world may depend on it.

¹Storm in a Teacup, Helen Czerski, Transworld Publishers, 2016

² Clarke et al., “Detection and learning of Floral Electric Fields by Bumblebees”, Science, 340, 6128, 66 (2013).

³The passages quoted are from paragraphs 215 and 225 respectively of Laudato Si which can be read online.

Sugar Pot can be found at 248 Kennington Park Road, SE11 4DA

Half way through…

talesfromthewormbin

What packaging does your coffee come in? Is it paper, compostable? The bits of packaging here are part of an experiment to see how long they will take to break down in a worm composting bin #talesfromthewormbin

The problem is oat milk. If you are having a go at living plastic free (or even reducing your reliance on single use plastic) during Plastic Free July, you have probably encountered at least one sticking point. Something that you are finding a little tricky to let go of. There are things that are too difficult to eliminate right now (meat/fish packaging is one example although there have been efforts to change this in some locations) but these are not necessarily sticking points. No, sticking points are things that seem that they should be easy to eliminate but for some reason are not. For me this is oat milk.

For the past three years, I have been participating in Plastic Free July with the aim of trying to find ways of living that reduce my plastic waste. And for the past three years, the problem has been oat milk. It is becoming a bit of a nemesis. Although proper, dairy based milk is available in glass bottles, this does not appear true for non-dairy based milks. Although some packaging can be recycled, it is a significant contributor to my waste pile. So, how about home made oat milk? It should be easy shouldn’t it?

oat milk, kone, filtering

Oat milk filtering through the Kone filter.

You can find plenty of recipes for oat milk online (a few are here, here and here) but I’ve always found it messy and, well, wasteful. The worms have enjoyed the oats in the past but surely there’s something better that can be done with them? Well, this year, things seem a bit different. And part of that is because of a coffee filter.

Years ago I tried the coffee Kone filter as an attempt to reduce my use of paper filters in the chemex. Sadly, I didn’t get on with the Kone. Unlike a paper filter, some sediment made it through the filter leading to more of an immersion type coffee drink rather than a filter. Consequently it went to the top of a cupboard and lay forgotten for a few years. Until this June when I re-discovered it as a filter for the oat milk. Rather than a muslin bag, the Kone can be cleaned easily and the whole process is significantly less messy (and slightly quicker – stirring the contents of the Kone with a spoon is easier encouragement to get the oat milk through than squeezing the muslin bag). Although there remains significant work before this can start to be a habit rather than just for a month, this July’s oat milk is a lot more promising than previous years. I’ll keep you updated as to whether the oat milk remains being home made in August.

pitch drop oat milk

Preparing your own dairy-free milk also offers new opportunities for watching physics such as the pitch-drop experiment here.

In the meantime, do let me know how you are getting on with your own Plastic Free July. Do you have any sticking points? On the other hand, are you finding that you are enjoying taking your re-usable cup around with you when you get a take-out coffee? Also, if you have any recipes for things that can be done with these left over blended oats. I’d love to hear of your culinary experiments.

In the following recipes, because I do not know how much oat milk you are making, I’ll call the amount of blended oats X g. In my experiments X has been either 115g or ~60g.

 

Oat and Apple Tarts

Xg blended oat left overs

Xg sugar

X/2 g flour

Pinch cinnamon and nutmeg to taste

teaspoon baking powder

Cooking apple (peeled and cut into smallish chunks)

 

Mix the blended oat left overs with the sugar and then stir in the flour, baking powder and spices. Spoon onto a greased baking sheet so that they make circular blobs of about 3cm diameter. Place the apple pieces into the mixture and bake at 180C for about 15 minutes until risen and slightly browned.

 

Sort of Flapjacks

X g blended oat left overs

X g sugar

X/2 g flour (but this isn’t really necessary).

Oat flakes, spelt flakes, sunflower seeds, pumpkin seeds, dried fruit, whatever you would like to put in a flapjack

Mix everything together, spoon into a lined and greased baking tin, bake at 190C for 15 minutes until firm. Keeps in an airtight container for days.

 

Hobnobby biscuits

home made oat biscuits

Not quite there yet. If you have a better recipe or can improve this one, please let me know.

A work in progress – the quantity of oats is not right yet and perhaps they need to be toasted oats or even spelt flakes.

X g blended oat left overs

X g sugar

X/2 g flour

teaspoon baking powder.

X-2X g oats

Mix the blended left overs, sugar, flour and baking powder together. Stir in the oats. Spoon on a lined and greased baking sheet so that you get ‘biscuit sized’ portions. Bake for 25 minutes at 190C or until brown.

 

Like clockwork at Doctor Espresso, Putney Bridge

Doctor Espresso Putney Bridge

There is a lot of physics in this photo alone, but there is even more to be seen if you visit this lovely little cafe.

“Isn’t it a thing of beauty?” So wrote Brian’s coffee spot review of the 1956 Gaggia Tipo Americana espresso machine found at the Putney Station branch of Doctor Espresso. And it is only possible to answer this question in the affirmative. There is something about a mechanical piece of equipment (particularly if it is shiny and has levers) that ignites a feeling of awe. Perhaps it is the awareness of the complexity of the tasks that, when traced through the machine, are revealed to be the result of a series of simple, but ingenious steps. Perhaps it is the feeling that it is possible for someone, one individual, to know inside out how the piece of equipment works and, if necessary, to build it. Perhaps it is because it is shiny. Nonetheless, I had been itching to go and try The Caffetteria, the Doctor Espresso café opposite Putney Bridge station for ages, since I chanced upon its review in Brian’s Coffee Spot. Trundling through the hot streets of London in a bus in this recent heatwave nearly made me reconsider and yet we ploughed on, finally arriving in this shaded spot in the mid-afternoon.

There is very little seating inside but the shade outside enabled us to take a seat by the window. A perfect location to watch people coming and going to and from Putney Bridge Station: who will pick up that 5p on the floor? Will anyone notice? There are a few more chairs and tables across the pavement next to the tree. Several cakes tempted us but we resisted, instead I enjoyed a (single) espresso, Italian style, very drinkable. There is something very relaxing about enjoying an Italian espresso in an independent (or at least very small chain) café. The café aims to “provide a tranquil environment for customers to relax and converse” and it would certainly appear to do so with odd pieces of decor and posters prompting different bits of conversation. The barista was very friendly and trusted us to enjoy our coffee outside before coming back in to pay. Perhaps this seems a small thing, but trust helps to build societies and small gestures of good, repeated, have a ripple effect on our world¹. A nice touch.

espresso Doctor Espresso Putney

The result.
A single espresso ready for enjoying.

Brian’s Coffee Spot describes the process of ‘pulling’ an espresso using this lever machine (the oldest working espresso machine in London apparently). The machine combines the beauty of the mechanical with the skill of the barista to produce a great coffee. This is not human vs machine but human working with machine to create something that others appreciate. A similar respect for the machine was expressed by the clock maker John Harrison about three centuries ago. Harrison had just made a clock that was able to keep time accurately over many weeks while at sea. His task was necessary because having a clock that accurately kept the time at the departure port  would enable a ship’s navigators to calculate their geographical position based on a comparison of this port time to the local time experienced by the ship. He was trying to solve the problem of ‘longitude’. Harrison had taken 19 years to develop his H3 clock which could keep time accurately at sea despite changes in temperature, humidity or rough conditions but within a few more years he’d produced the H4 (which can now be seen in the National Maritime Museum). Significantly smaller than the H3, Harrison said of it:

“I think I may make bold to say, that there is neither any other Mechanical or Mathematical thing in the World that is more beautiful or curious in texture than this my watch or Time-keeper for the Longitude…”²

Enjoying coffee in the company of posters

A conversation piece? The physics of buoyancy or the deceptions of marketing. You could spend a long time at Doctor Espresso thinking about these things.

Harrison lived before espresso machines were invented. Self-taught, Harrison designed and built his own clocks. How many of us would be able to do that? Although we wear watches, how many contain batteries and other components that produce a simple action (showing the time) by complex means. The opposite of what we admire in the lever operated espresso machine. Each individual element may be elegant, but as a composite it can be ugly, however aesthetically satisfying. Harrison built his first clock before he was twenty years old and almost entirely out of wood. Working on the basis of a pendulum, he ensured that the cogs did not wear down as they may be expected to do by utilising the grain of the wood and by using only fast growing oak². Why would this make a difference? Trees that grow fast will have well separated growth rings. As the ring is an area of weakness in the wood, a fast growing tree would have a lot of solid wood compared to a relatively small number of rings, thus affecting the structural properties of the cogs. Moreover Harrison’s wooden clocks did not need oiling because those bits that needed oiling were carved from a tropical hardwood that exuded its own grease. In later clocks Harrison was to overcome the problem of the varying temperature experienced at sea by inventing the bimetallic strip. Two metals of different thermal expansion coefficients placed on top of each other, this simple piece of kit is essential for all sorts of modern machinery including, probably, the espresso machine sitting beautifully at Doctor Espresso.

A warm afternoon in a café of such elegant machinery offers plenty of opportunities to ponder the world of clockwork and levers. Do we understand how having a clock would allow us to calculate our geographical position? What about latitude? How many of us could do this for ourselves? And as we check the time while finishing our espresso, how many of us can appreciate the simplicity that leads to complexity and build our own?

 

¹A bit of cod-philosophy formed by combining bits from Pope Francis’ encyclical Laudato Si’ with Paddington 2.

²Quoted from “Longitude”, Dava Sobel, 1995

Doctor Espresso’s Caffetteria is at 3 Station Approach, SW6 3UH

Drip coffee

The universe is in a cup of coffee. But how many connections to different bits of physics can you find in the time it takes you to prepare a V60? We explore some of those links below while considering brewing a pour-over, what more do you see in your brew?

1. The Coffee Grinder:

coffee at VCR Bangsar

Preparing a V60 pour over coffee. How many connections can you find?

The beans pile on top of each other in the hopper. As the beans are ground, the bean pile shrinks along slipping layers. Immediately reminiscent of avalanches and landslides, understanding how granular materials (rocks & coffee beans) flow over each other is important for geology and safety. Meanwhile, the grinding itself produces a mound of coffee of slightly varying grain size. Shaking it would produce the brazil nut effect, which you can see on you breakfast table but is also important to understand the dynamics of earthquakes.

Staying at the grinding stage, if you weigh your coffee according to a brew guide, it is interesting to note that the kilogram is the one remaining fundamental unit that is measured with reference to a physical object.

2. Rinsing the filter paper:

V60 chromatography chemistry kitchen

A few hours after brewing pour over, a dark rim of dissolved coffee can be seen at the top of the filter paper. Chromatography in action.

While rinsing the filter we see the process of chromatography starting. Now critical for analytical chemistry (such as establishing each of the components of a medicine), this technique started with watching solutes ascend a filter paper in a solvent.

Filtration also has its connections. The recent discovery of a Roman-era stone sarcophagus in the Borough area of London involved filtering the excavated soil found within the sarcophagus to ensure that nothing was lost during excavation. On the other hand, using the filtered product enabled a recent study to concentrate coffee dissolved in chloroform in order to detect small amounts of rogue robusta in coffee products sold as 100% arabica.

3. Bloom:

bloom on a v60

From coffee to the atmosphere. There’s physics in that filter coffee.

A drop falling on a granular bed (rain on sand, water on ground coffee) causes different shaped craters depending on the speed of the drop and the compactness of the granular bed. A lovely piece of physics and of relevance to impact craters and the pharmaceuticals industry. But it is the bloom that we watch for when starting to brew the coffee. That point where the grinds seem to expand and bubble with a fantastic release of aroma. It is thought that the earth’s early atmosphere (and the atmosphere around other worlds) could have been helped to form by similar processes of outgassing from rocks in the interior of the earth. The carbon cycle also involves the outgassing of carbon dioxide from mid-ocean ridges and the volcanoes on the earth.

As the water falls and the aroma rises, we’re reminded too of petrichor, the smell of rain. How we detect smell is a whole other section of physics. Petrichor is composed of aerosols released when the rain droplet hits the ground. Similar aerosols are produced when rain impacts seawater and produces a splash. These aerosols have been linked to cloud formation. Without aerosols we would have significantly fewer clouds.

4. Percolation:

A close up of some milk rings formed when dripping milk into water. Similar vortex rings will be produced every time you make a pour over coffee.

Percolation is (almost) everywhere. From the way that water filters through coffee grounds to make our coffee to the way electricity is conducted and even to how diseases are transmitted. A mathematically very interesting phenomenon with links to areas we’d never first consider such as modelling the movements of the stock exchange and understanding the beauty of a fractal such as a romanesco broccoli.

But then there’s more. The way water filters through coffee is similar to the way that rain flows through the soil or we obtain water through aquifers. Known as Darcy’s law, there are extensive links to geology.

Nor is it just geology and earth based science that is linked to this part of our coffee making. The drips falling into the pot of coffee are forming vortex rings behind them. Much like smoke rings, they can be found all around us, from volcanic eruptions, through to supernovae explosions and even in dolphin play.

5. In the mug:

Rayleigh Benard cells in clouds

Convection cells in the clouds. Found on a somewhat smaller scale in your coffee.
Image shows clouds above the Pacific. Image NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response

Yet it is when it gets to the mug that we can really spend time contemplating our coffee. The turbulence produced by the hot coffee in a cool mug prompts the question: why does stirring your coffee cool it down but stirring the solar wind heats it up?

The convection cells in the cooling coffee are seen in the clouds of “mackerel” skies and in the rock structure of other planets. The steam informs us of cloud formation while the condensation on the side of the cup is suggestive of the formation of dew and therefore, through a scientific observation over 200 years ago, to the greenhouse effect. The coffee cools according to the same physics as any other cooling body, including the universe itself. Which is one reason that Lord Kelvin could not believe that the earth was old enough for Darwin’s theory of evolution to have occurred. (Kelvin was working before it was known that the Sun was heated by nuclear fusion. Working on the basis of the physics he knew, he calculated how long the Sun would take to cool down for alternative mechanisms of heating the Sun. Eventually he concluded that the Sun was too young for the millions of years required for Darwin’s theory to be correct. It was the basis of a public spat between these two prominent scientists and a major challenge to Darwin’s theory at the time).

 

Of course there is much more. Many other links that take your coffee to the fundamental physics describing our world and our universe. Which ones have you pondered while you have dwelt on your brew?