Category: Coffee review

Categories
Coffee review Observations Sustainability/environmental Tea

Breathing underwater at the London Particular

table and inside of the LP
Inside the London Particular

Tucked out of the way in New Cross, the London Particular has always been just that little bit far away to travel to, but always so tempting, a siren calling towards New Cross. The reviews of the food and the place were intriguing, while the coffee is roasted by HR Higgins, a roaster with a café that always seems closed when I get the opportunity to pass by (which is usually Sundays). So it was with some relief that I finally managed to get to the “LP” a couple of weeks ago. Towards the end of a row of shops, the space outside the café has plenty of seats where you can enjoy a spot of lunch and/or a coffee on a warm day. Inside feels more cosy. A bar on the left of the entrance forms a corridor with the wall that you walk through to get to a room with communal table at the back. In addition to the communal table, there are a series of individual high chairs along the wall. At the back of the café is a window with an old device sitting on it. “An old digital multi-meter” I said before being corrected by my sometime companion in these reviews, it has a dial, it must be an “analogue multi-meter” then! It did seem to be able to measure current and resistance and it did have a dial to indicate the value measured. Quite why it was sitting, unconnected, on the windowsill is anyone’s guess.

AMM, LP, NC
An Analogue multi-meter. But why was this sitting on the windowsill at the back of the cafe?

The lunch menu is good. Enough items there to provide choice, few enough that each can be done well. Significantly, the true London Particular, the pea soup, was not on the menu on the day we were there. We had a light bite of lunch, a black coffee and shared the jug of mint infused tap water that was placed on our section of the table. At the other end of the table, another customer was enjoying her lunch. So although communal, the table gave us enough room to be private and have our own conversation. A mirror along the wall above the table reflected the blackboard menu between the table and the bar. Thinking about mirror writing reminded me of Dr Florence Hensey and his letters of lemon juice ink. Back in the eighteenth century he had operated as a spy out of coffee houses on the Strand and in St Martin’s Lane¹. Spying on England for France, his letters, written in lemon juice (invisible ink) passed without detection before the frequency of correspondence drew suspicions. Times move on. Spies would surely no longer write in lemon juice or even mirror writing to avoid detection.

Lunch on a week day was a very good time to experience this café. It must get quite crowded at weekends or brunch times. So it was good to be able to sit back and contemplate our surroundings from the back of the café. In the foreground of our view though was the water jug. With fresh mint leaves stacked inside, it was evident that air had become trapped under some of the leaves forming tiny bubbles. How had the air got stuck there? Was it merely that the leaf was blocking the air bubble from rising through the water? Could there be slightly more to it?

Coffee and mint water in New Cross
Coffee and mint water at the LP

There is a popular expression “like water off a duck’s back”. Perhaps it arose because the duck’s back is often thought one of the most waterproof surfaces we know. But what makes the duck so waterproof? Why does water just form drops and then fall off the back of the duck? It is not because the feathers are oily. We sometimes ‘wax’ our waterproofs with a grease to make them resistant to getting wet and so perhaps we have thought that the duck’s back was just a bit greasy? And yet a study done back in 1944 showed that mere oil could not account for the waterproofing of the duck’s back.

Before delving into why the duck’s back is such a waterproof surface, it’s helpful to know how to quantify ‘waterproof-ness’ in the first place. To measure how waterproof something is, we use what is known as the contact angle, which is the angle that the drop makes with the surface on which it is sitting. Surfaces that are not waterproof (technically we call them “wettable” or hydrophilic), have very low contact angles, the ‘droplets’ of water on the surface are flattened. Waterproof surfaces on the other hand (imaginatively called hydrophobic), have contact angles which are much greater than 90º (it may be helpful here to have a look at the cartoon illustrating this point). Droplets that formed on a duck’s back had contact angles much greater than 90º, indeed, they formed almost spherical drops of water. What could be going on?

artemisdraws cartoon, contact angle, wettability
How ‘wettable’ a surface is can be defined by the contact angle that the drop makes with the surface. Image thanks to artemisworks.

The answer is in the details of the feather. The feather is not a flat surface but a material that has irregular protrusions and structure at the micro and nano-scale (one thousand and one million times smaller than mm scale respectively). These protrusions trap air within the feather and so effectively suspend the drop above the feather surface. The droplet does not have a flat surface on which to spread out. The structure means that the contact angles of the drops of water on a feather can be even higher than 150º; the droplets are held up almost as if they are spheres of water.

mint infused water at the LP New Cross
A breath of fresh air under water. Air bubbles trapped under mint leaves.

Another creature that uses the irregular protrusions on the hairs on its legs for waterproofing is the spider. The hairs on the legs of a spider mean that, just as the duck’s back, the spider’s legs are extremely waterproof. But it also means that air is trapped under the droplets. Consequently, if a spider finds itself submerged under water, the air under the droplets forms little bubbles similar to those under the mint leaf in the London Particular. And this allows a drowning spider the air it needs to breathe. Nanostructure helping the duck to dive and the spider to survive. And the mint water to be particularly refreshing on a warm day in a very pleasant place for a spot of lunch and a coffee.

 

 

 

The London Particular can be found at 399 New Cross Road, SE14 6LA

¹London Coffee Houses, Bryant Lillywhite, Pub 1963

Categories
Coffee review Observations Science history Sustainability/environmental Tea

Looking under the surface at Mughead coffee

Mughead Coffee, Coffee in New Cross
Set back from the busy A2, Mughead Coffee offers a space to unwind.

A new café has just opened in New Cross. Mughead Coffee opened in July 2017 and sits fronting the A2, part of an old Roman road connecting London to Dover. The large pedestrianised space outside the café provides plenty of room for a few tables together with some further chairs arranged along the café window. It also means that the cafe is set-back far enough from the road that it is possible to sit outside and enjoy the surroundings. Inside, there were plentiful seats but, sadly equally plentiful numbers of occupants relaxing in this new cafe. Clearly this new coffee place in New Cross is proving popular. And why not! Just down the road from the London Particular, Mughead Coffee serves Square Mile in a friendly atmosphere. It is easy to see this becoming a popular local haunt. The usual array of coffees were on offer together with a filter option but as we arrived shortly after lunch, the cake/edible option appeared a little depleted. The interior of the café is quite light and airy with comfortable chairs at the back and more regular seating towards the front. We ordered a long black and a ginger beer and then adjourned to a table outside to await our drinks.

The tables outside are arranged on a sloping pavement. This is not really a big deal, but did remind me of a comment made by the lecturer who was trying to instil experimental design into us as undergraduates: The only stable table is a three legged one. However there was not much time to reflect on that as very soon both coffee and ginger beer arrived with a glass of ice. The natural light revealed the oils on the surface of the coffee as they moved with convection. Different convection zones moving in the coffee just as air parcels do in the sky to form mackerel skies or hot lava moves to form different rock formations, both on Earth and elsewhere.

coffee and ice in New Cross on a wooden table
Coffee and ice at Mughead Coffee. Note the reflections on the coffee surface.

Once the ginger beer was poured into the glass, the ice cubes floated upwards with just a fraction of them bobbing above the surface, the majority of the ice cube beneath. A glance around our surroundings revealed other hints of sub-surface structures. A drain cover nearby indicated, together with some tiling along the pedestrianised zone, the line of the rain sewer running along the road. A public telephone box had no wires obviously leading from it meaning that all the wiring for the communication had to be subterranean. And a raised flower bed, full of thriving plants, had a little drainage hole right at the bottom in order that heavy rain storms did not drown the plants.

This last feature reminded me of a documentary I’d recently seen concerning climate change. Often we tend to think of climate change as involving things that we can see: the melting of glaciers or the disappearance of sea-ice, or freaky rain storms that cause local flooding. However there is another aspect, a sub-surface aspect, that has perhaps been far more visually alarming than even the break-off of the Larson A, B and C ice shelves. If only we could see it. The problem is that, as it happens below the surface of the sea, few of us see it, it is hidden from view and therefore easily hidden from our conscience. It is the drastic effect that rising sea water temperatures are having on a particularly unusual plant-animal combination, the coral reefs. Coral reefs such as the Great Barrier Reef just off Australia, are animals that exist in a symbiotic relationship with a particular type of algae called zooxanthellae. Although the ‘mouths’ of the coral eat passing zoo plankton at night, during the day, they get other nutrients from the photosynthesis products produced by the zooxanthellae that live within their skeletons. These plants give the corals those amazing colours (as well as food). In return, the coral provides the plant life with shelter (they live within the coral itself) and extra carbon dioxide.

Outside Mughead Coffee New Cross
Indications of a hidden architecture. Can you see the drainage hole at the bottom of the planter at the back of the photo?

As the sea temperature rises, the zooxanthellae become less efficient at photosynthesising and so of less use to the coral. If the temperature stays high, the coral ejects the plant life from its body causing the coral to lose all its colour, it has bleached. What sort of high temperatures are needed? It seems that if the temperature of the water is about 1-2°C above the usual seasonal maximum, the coral are ok for a few weeks. But if the temperature rise is 3-4°C (or higher) above the usual seasonal maximum, the damage can occur in just 2 days¹. Coral bleaching does not necessarily lead to coral death but if the bleaching is sustained vast areas of coral reefs can die and get destroyed, with significant impact to the local ecosystem. As corals host “nearly one-third of the world’s marine fish species…”² this impact will be far reaching and affect the livelihoods of millions of people³.

Although small scale coral bleaching has been documented since 1979¹, the first global scale coral bleaching occurred in 1998. It was 12 years until the next global bleaching event occurred in 2010. Following that, we have just had the third global bleaching event in 2015-16. In the latest episode, it is estimated that 29% of the Great Barrier Reef’s coral died (as in actually died, not just bleached). These temperature increases can be associated with global warming caused by increased greenhouse gases in the atmosphere (for more info click here (opens as pdf) or refer to [4]).

The frequency of these events, together with the fact that there were no global bleaching events prior to 1998 should be a dramatic warning siren calling on us to do something to arrest climate change. But what can be done and is it already too late? Well, it is not yet too late to do something. The plants, thriving in the box in front of Mughead can emphasise to us the importance of maintaining our local environment and by extension our global one. Taking time to slow down and take stock of what is beautiful in our environment, and the habits we need to develop to keep this for future generations, these are things that we can do. If you eat fish, was it caught sustainably? Some fishing methods can kill the coral reefs, check before you eat. This is not going to be hard to do. After all, we already do this with coffee. Many coffee drinkers (and roasters) will check how the coffee is grown and processed for both environmental cost and the conditions experienced by the farmers. Many such small actions can cumulatively build to an effort to stop climate change.

Which brings us, in a sense, back to the surroundings at Mughead Coffee. Sitting down and taking time to enjoy that coffee while appreciating our surroundings, the visible and the hidden, the busy road and the mini-oasis of plants in the planter, may help us to see that connectedness that pushes us to accept our responsibility to our common home. Contemplating the history of the road in front of us, will our planet still be beautiful in another 2000 years? With an offer of “gourmet sandwiches” on the menu (if only we’d got there early enough), there’s plenty of reason to head along to the old road in New Cross and sample the coffee while pondering our own impact on this interesting location.

 

¹ Life and Death of Coral Reefs, Charles Birkeland (Ed), Chapman & Hall, 1997

² Coral Reef Conservation, Ed Isabelle M Côté and John D Reynolds, Cambridge University Press, 2006

³ Chasing Coral, Netflix Documentary, 2017 (see trailer below)

4 Climate and the Oceans, Geoffrey K Vallis, Princeton University Press, 2012

Chasing Coral Trailer:

 

 

Categories
Coffee review Coffee Roasters Observations slow Sustainability/environmental Tea

Cobwebs, Crows & Coleman Coffee, Lower Marsh

filter, Brazilian or Guatemalan, V60, rainbow, glass, Coleman Coffee, Lower Marsh, Waterloo
There’s a lot of physics in this glass cup of coffee, enjoyed at Coleman Coffee, Lower Marsh.

Coleman Coffee on Lower Marsh, Waterloo, is a surprisingly relaxing place. Surprising because the frontage gives little away. A door with windows on either side revealing a small wooden bench on the right and a larger table on the left. A food menu is on the left, the coffee menu in front of you (above the counter) and a note about how the coffee is roasted on a black board on your right. The space feels open and welcoming but it is the garden at the back that I think shifts Coleman Coffee from being a lovely little café to a great spot at which to just spend time and notice things.

My first visit was on an incredibly hot day in early July. For some reason I didn’t see the filter coffee option on the menu and so chose a long black to enjoy outside. The shade of the trees was a welcome respite to the hot Sun and the contrast created by the light provided much to dwell on with the inadequacies of my phone’s camera. Berries had formed on the tree growing up the wall of the café. After my visit I read the review of the café on Brian’s Coffee Spot and realised that these berries were mulberries. The other trees providing the shade were a Jasmine and a Pomegranate. I also found that I had missed the filter option and so a return visit was obligatory! How easy it is not to notice things.

ditch the plastic straw, enjoy a paper one
Chocolate milk and a paper straw.

A second visit sadly revealed the restricted opening hours of Coleman Coffee. Arriving at about 2.58pm, we were told it was take-away only as they were closing at 3pm. However the third visit was worth the wait. By this time the weather had turned and it had been raining, but the garden was still calling. The filter coffee on offer (V60) was either a Brazilian or a Guatemalan. Opting for the nuttier of the two (an allergy to actual tree nuts does not prevent my enjoying nuttiness in coffee!), we took a couple of glasses of water through to the back and awaited our drinks. When they arrived, it was interesting to find that the nutty coffee was truly nutty. A lovely flavour and mouthfeel to enjoy. It was also great to notice that the straw in the chocolate milk seemed to be an old-fashioned paper straw (rather than the environmentally problematic plastic straws). As it had rained, the stools outside were a little wet, even though they had been largely sheltered by the same trees above the garden. This time, the mulberry tree seemed mulberry-less, apart from the one berry lying sorrowfully on the floor. The red of the berry being squished (accidentally) underfoot leaving it lying and injured in the style of Pyramus and Thisbe. Across the other (wetter) side of the garden, three spiders were busy weaving new webs, ready to catch whatever flies came their way. It would have been easy to watch those spiders for hours but I think a good café can linger in the memory long after your visit has ended and so the spiders are still spinning their webs in my mind now.

garden spider at Coleman Coffee Waterloo
Spider on the table. What could be better than time spent contemplating their webs?

Photos of spiders webs glittering with dew drops are common place but somehow strangely attractive. Beads of dew gather at various points on the web leading to descriptions of cobwebs as being laden with jewels. A few years ago, a scientist contemplating spider’s webs asked why it was that water collected like jewels on the webs? Why didn’t it collect similarly on your hair? (You can read more about his story here). The team looked at the webs of one particular spider with an electron microscope. Electron microscopes can magnify things far more than optical microscopes (for images of coffee under an electron microscope click here) and so the scientists were able to observe how the hydrophilic (wet-able) fibres in the web turned from ‘puffs’ to ‘knots’ as they got wet. Water falling on the web was then attracted to these knots, partly due to an effect caused by the knot shape and partly due to the surface tension gradient of the water along the fibres. The results of the study can be found here.

Although it took five years of investigation after the initial contemplation, this study of spider’s webs could lead to tools that could be used for water collection or in devices to aid chemical reactions. Which brings us to the other ‘C’ of the title: crows. Sadly there were no crows in the garden on either of my visits to Coleman Coffee. Nonetheless there is a link. My first visit had been cut a little short as I was headed to the Royal Society Summer Science Exhibition. Apart from the fact that it was baking hot inside the Royal Society, this science outreach event had a good mix of science/experiments for adults and for kids, it was great to wander around and learn a large number of new things. So many exhibits caught my eye but the one that connects with Coleman’s and cobwebs was the exhibit on tool making crows.

Spider and web, Coleman
Spider building a web at Coleman Coffee

Crows have been shown to be great tool users. Particularly the New Caledonian Crow which has been shown to even make hooks out of twigs in order to fish out insects from their hiding places. While thinking about what it was that led to this species of crow becoming adept at tool use (and therefore perhaps an explanation of human tool use), it became apparent that the two particularly good tool using crow species lived on remote islands without predators. Not only did they have the physical ability to create tools (a straight beak for crows, a thumb for humans), they lived in a place where they could have time to explore and to create, to develop tools to enable them to get the most tasty bug.

Just as the scientists had needed time to watch, to investigate and to think about spiders webs in order to create new tools, so crows may have needed that time to explore their tool use. Perhaps it’s worth pushing the analogy to inner-city London (or indeed wherever you are). The more we spend time out, contemplating and enjoying nature, the more productive we can be. But to develop, we need to slow down, to think, to contemplate, and to enjoy great coffee in surroundings as special as at Coleman Coffee.

Coleman Coffee is at 20 Lower Marsh, SE1 7RJ

Categories
Coffee review Science history slow

Coffee & temperance at the Penny, Old Vic

inside the Penny Old Vic
Coffee at the Penny

A café with good coffee in a theatre? I admit to being a little dubious when I first read about Penny at the Old Vic. Fortunately, there was no reason to be concerned. Penny serves Workshop coffee in an unusual setting (even accounting for the fact it is in a theatre). Going through the doors to the Old Vic, you turn left and head down a staircase to the basement where a long counter stretches out in front of you and to your right. Being a theatre café, there were a wide selection of snacks, bar meals, beer and wine in addition to the coffee being served with the La Marzocco espresso machine. As you’d expect, the usual range of coffees were on offer but if you prefer non-dairy milk, there was oat and almond available in addition to the more usual soy based milk. (Although almond milk is one to watch for if you have a tree-nut allergy as there is a risk of cross contamination).

There was also a wide selection of chairs and tables to choose from, ranging from a standard table, to a high table with stools and, around the corner, some chairs that look like you can sink into them and enjoy your coffee way after the performance has been called. The café is open all day (in fact from 8am until 1am on week days) and, if you are not there during a performance is quite spacious (though during the intervals it could probably get quite crowded).

staircase, Old Vic
The lighting on the staircase periodically got brighter and then dimmer. How easy is it to keep our national electrical supply constant such that blackouts and brownouts are not a problem?

The café certainly provides a service for good coffee in Waterloo (it’s within 5 minutes walk from the station) and it is a great place for refreshment if you are visiting the theatre, but is it also the sort of place at which you can slow down and enjoy the moment? The type of neighbourhood café where you can sip your coffee while letting your mind wander onto a café inspired thought train? At first glance, it is perhaps unpromising as it has clearly been renovated and made to be a modern café. But then, thought trains do not happen “at first glance” but as a result of slowing down, sitting, watching and absorbing the surroundings. It is as you do this that I think Penny at the Old Vic starts to speak to you.

The first thing that you may notice is the lighting. A number of different types of lightbulb including an industrial looking art-piece on the stairwell coupled to what appeared to be natural light coming down through another staircase. This theatre was first built in 1816-1818¹ (but with significant rebuilds since then), how was the stage lit at that time? Where did the theatre patrons go to get a cup of coffee or a glass of wine between the scenes and how could they see anything in the dark?

Around 3.5 miles away, one of the first housing developments to have electric lighting was being constructed in the 1860s. The electricity was supplied by seven steam engines housed in a building just off High St Kensington and sent to the new development next door, “Kensington Court”¹. Evidence of the electrical power station (which supplied DC not AC electricity) can still be seen on a stone sign on the building alerting passers by to the “Electric Lighting company”. It is probable that no such set of steam engines provided power for the lighting in the Old Vic, which was more likely still run on candles and gas lighting. However, it is something that was nearly contemporary with the development of Kensington Court that gives this post its title. It is also the reason behind the name of the cafe.

Soya hot chocolate at the Penny, Old Vic
Lord Kelvin got thinking about viscosity as a consequence of drinking a hot chocolate.

In the 1880s, a woman called Emma Cons took control over what is now the Old Vic. When she ran it, the theatre was called the “Royal Victoria Hall and Coffee Tavern” and ran ‘morally decent‘ productions for local people (note though the importance of the coffee to the project!). These productions included scientific lectures for which the entrance fee was a penny, hence, apparently, the Penny café. Apparently she also ran science classes in the disused dressing rooms and, though the mind boggles as to what experiments were done in this theatre at that time, the classes and the lectures were so popular that soon, Cons founded Morley College to continue this adult education. Morley College continues as an adult education college to this day and is now one of London’s oldest adult education colleges.

So it would appear that, even though the Penny café is a relatively new addition to the Old Vic theatre as we know it, the associations between the theatre and coffee (and the theatre and science) go back a long way. First appearances can be deceptive and, with good coffee and much to ponder, the Penny is definitely one to sink into a chair and to listen.

Penny café is in the Old Vic Theatre, The Cut, Waterloo, SE1 8NB

Inside the Penny
Penny at the Old Vic.

¹The London Encyclopaedia, 3rd Edition

Categories
Allergy friendly cafe with good nut knowledge Coffee cup science Coffee review Home experiments Observations Tea

Coffee chemistry at Estate Office Coffee

Could it really be true that the tables were reclaimed school science desks? I had read a review of Estate Office Coffee by Beanthere.at on London’s Best Coffee that had made this surprising claim (together with favourable comments about the coffee and cakes). Like a red flag to a bull, a visit was inevitable. Would there be any clues left on the tables as reminders of the past history? In the absence of many photos of the interior of the café, my mind wandered to images of long wooden benches like the physics labs in my old school. I imagined enjoying a coffee at such a bench, seated on a wooden stool, my feet not able to reach the ground. So when I arrived outside the cute little building, I was a bit puzzled as to how a whole lab could fit inside! Going in, my images of rows of coffee-table-lab-benches were metaphorically thrown out the window. Instead, a set of modern looking (small) tables were arranged so that several groups of 2-4 people could sit and enjoy their coffee together or individually. A lovely, friendly, space for conversation with friends but not quite the lab I had imagined. The counter, which was on the right as we entered, had a great array of muffins and cakes arranged on it which proved irresistible (and they knew which allergens were in which cake, so a definite tick in the ‘allergy friendly’ café box). The coffee (from Allpress espresso) was also very good and we ‘retired’ to a table to enjoy coffee and cake together.

interior Estate Office Coffee
Clearly science labs have changed since I was at school! The tables in Estate Office Coffee are reclaimed lab benches.

Although warm that day, sitting near the window was a very pleasant way of slowing down and noticing things. Moreover, the local history that is framed on the wall near the door, provided an interesting diversion for understanding how this quirky building came to be (and to survive in its present form). Copies of Caffeine magazine were also lying around adding to the large number of things that you could think about rather than revert to checking your phone. Finally though, curiosity got the better of me and I asked, were the tables really old school science lab benches? The helpful barista wasn’t absolutely sure and so texted the owner to enquire. Fairly quickly an answer came back: yes indeed, the wood had been reclaimed and used to be laboratory benches. Either school science labs have changed a bit since I attended or the tables have undergone a refurbishment as well as a reclaim, but nonetheless what a feature! Together we looked underneath the tables and noticed the parallel grooves running along the underside of the wood. What were they used for? Pens? Drainage channels for spilt chemicals? The mind boggled. But then returning to our table, we noticed that despite the lovely varnish and careful refurbishment, our table showed evidence of previous science lab use. Two circular stains as if the wood varnish had been etched by a strong acid. Immediately this took me back to experiments-gone-wrong with a home chemistry set but then it set off a whole different thought train through a slightly lateral connection to acidity and coffee.

table detail, inside Estate Office Coffee
Evidence of a past life?
Two rings in the varnish on one of the tables at Estate Office Coffee.

The issues and science associated with acidity in coffee have been discussed many times elsewhere and so if you would like to follow that train of thought you can do so here or here. Instead, I was reminded that the Arrhenius definition of acidity was that of a substance that, when in solution, increased the concentration of H+ ions in the water. For reasons that will become clear, this reminded me of stories I had heard of expert coffee-tasters who always use the same spoon when cupping coffee. Were there actually very good reasons that these coffee tasters always insist on using their own, same spoon, in every cupping session?

The connection between acidity and the spoons used for cupping comes via the ability of substances to gain or lose electrons to become ions. In the case of acids, the ion is H+ but different elements form their ionic counterparts more or less easily. This means that it is easier to take two electrons from the element copper (Cu) to form Cu2+ than it is to remove one electron from gold (Au) to form Au+. The ‘ability’ of a substance to gain (or lose) electrons is measured by the standard electrode potential. A few years ago, a group at the Institute of Making investigated whether different teaspoons made from different metals tasted different. In a blind taste test involving 32 participants, not only did they find that the spoons tasted different (as measured by bitter, metallic, strong etc), those metals that were more likely to form ionic species in solution (as indicated by the standard electrode potential) consistently tasted more bitter and more metallic than the rest: copper and zinc teaspoons tasted metallic, chrome and stainless steel tasted the least.

coffee at EOC Streatham
The important thing is how this tastes. What is the influence of cup size, shape, colour on your perception of the taste of coffee?

What was more interesting though was that the investigators then turned to the question: does the type of spoon used influence the taste of a substance? Although they investigated ice cream rather than coffee, the tastes they were looking at (bitter, sweet, salty, sour) are very relevant to coffee tasting. Again, the authors did a study involving a series of blind taste tests, this time involving 30 participants. Again, the teaspoons used were identical to each other apart from the fact that each had been electroplated with a different metal (gold, copper, zinc or stainless steel). Again there appeared to be a dependence between the taste of the substance (ice cream) and the standard electrode potential of the metal used for the spoon. When the ice cream (which had been separately flavoured to be more salty, bitter, sweet, sour or left plain) was blind-tasted with zinc or copper spoons, the ice cream was consistently rated more bitter than when tasted with stainless steel spoons. But there was more, it seemed that the sweetness of sweet ice cream was enhanced by the copper and zinc spoons. Indeed, copper and zinc spoons seemed generally to enhance the dominant taste of the ice cream (sweet became more sweet, salty more salty etc). Although spoons made of these two metals were also rated as tasting metallic, the most pleasant blind-tested ice cream-spoon combination was the sweet ice cream tasted with the copper or zinc spoons.

So it would appear that the material that the spoon is made from could influence our perception of the taste of the food or drink we consume with it. The taste of coffee could be influenced by the type of metal spoon that is used to taste it with. Other studies have emphasised the psychological importance to taste of the appearance or weight of the spoon. For consistent cupping therefore, it may very well be a good idea to stick to your favourite spoon.

However, this seems an area in which anyone can do a bit of kitchen-top coffee science experimentation. Have you blind taste tested several coffees? What about different coffees with different spoons? For those who cup coffee regularly it would be fascinating to hear your thoughts on the influence of the spoon on the taste of coffee. For those of you new to coffee cupping, you can find a how-to at the bottom of this post and then please do share your experiences. In the meanwhile, you may be pleased to return in our imaginative journey to Estate Office Coffee where a great tasting coffee can be enjoyed in a non-metallic cup and where you may additionally pause to ponder the influence of your surrounding environment on the pleasure you derive from your coffee.

Estate Office Coffee can be found at 1 Drewstead Road, Streatham, SW16 1LY

 

 

 

Categories
Coffee review General Observations

Batch and CrO2 (Streatham)

coffee in Streatham
Batch & Co, Streatham Hill

A short while ago, on the advice of London’s Best Coffee (and Beanthere.at), I headed along to Streatham to try a couple of cafés including Batch & Co along Streatham Hill Road. The café is quite modern and cubic with plenty of tables at which to sit and enjoy some good coffee and food. Another interesting recommendation from these sites to add to the list. The counter is on the left as you enter and there was a good selection of cakes on offer that day. Is it possible to have too much cake in one day? Sadly, possibly it is and so, as I had already had my fill of cake at a previous café, I kept with just an Americano (roasted by Caravan). Tap water (infused with mint) was available at each table which was greatly appreciated on such a hot day as the one on which we visited.

There were many things to notice in Batch and Co. The street/bus sign above the counter, the large selection of books in the corner (what a shame the seats next to the shelves had been occupied already!), the corrugated zinc walls and then, the cassette tapes on the tables. What a blast from the past. Sadly these tapes were no longer being used to store music but instead as table number indicators. Now ordinarily, I think these cafe-physics reviews should be the sort of science that is accessible to everybody, the sort of observation that anyone could make. But today, today the temptation is just too great, because these cassette tapes are linked to something that is being researched in an obscure but very novel effect that just happens to be an area of research for me. So today, I hope you will stay with me as I take you from Batch & Co to a very odd effect that happens when things (cassette tapes) get very cold.

coffee and cassette tape in Batch and Co
Coffee and tape. Who knew how special the tape material would be?

Those cassette tapes used to work by writing and reading magnetic information. So the actual tape bit needs to be a magnetic material. The first generation of tapes were made with ferric oxide (Fe2O3) but later, and seemingly better, music tapes used chromium dioxide, CrO2, as the tape material. Nowadays the technology of tape cassettes has been superseded by other media but the material CrO2 lives on, it turns out it is a very odd type of material.

Just like iron, chromium dioxide is magnetic, which is why it was used in tapes. But chromium dioxide is a very special type of magnet in that it is what is known as a fully spin polarised magnetic material. To understand what that means, it’s helpful to compare it with iron or copper or indeed, any other metallic material that you can think of. Metals conduct electricity because the electrons in them are free to move from one contact to another and hence carry a current. Electrons are negatively charged particles but they also have a property called “spin”. Although spin is associated with angular momentum (rotation), it is fundamentally a quantum mechanical property of subatomic particles and so shouldn’t be thought of as being about the electron’s rotation on its axis (rather like the Earth rotates). Indeed, it seems that this quantum mechanical property of “spin” is something that is very hard to pin down, even amongst physicists (see here). So instead, generally speaking, we just think about spin having two ‘directions’: spin up and spin down.

tape supporting a table, Batch and Co
An alternative use for a cassette tape. Poor tape.

Ordinarily, the electron spin doesn’t have that much effect on how much current the metal can carry (its ‘resistance’). Indeed for most metals, the number of spin up electrons is roughly equal to the spin down ones. However this is not true of chromium dioxide. Although it is a metal, all of the electrons that conduct the electricity through it are of one spin type. All the electrons are either ‘spin up’ or they are all ‘spin down’. This is spin polarisation. It is something that could never happen in copper.

There are many reasons that this could be interesting, both technologically and purely from the perspective of it being quite beautiful physics. What turns it from interesting to a really big question though is what happens when chromium dioxide interacts with another set of materials, superconductors.

Superconductors are materials that can carry large amounts of current with zero electrical resistance. This property makes them great for things like MRI machines in hospitals where large magnetic fields require the sort of currents superconductors can carry easily. How they are able to do this gets a bit complicated but what is crucial for this subject is the fact that to conduct a supercurrent they need to have zero spin polarisation: they need to have equal numbers of spin up and spin down electrons. (If you are interested in how superconductors superconduct you can read more about them here and here).

cassette tape at Batch and Co
Who knew that this tape was so special?

Now imagine, you have a wire of a superconductor such as very cold niobium (all spins are equal) that you connect to a wire (or a tape) of chromium dioxide (only one spin possible). You may think that if you tried to pass an electrical current down that connection there would be a problem. And you would be right: To conduct electricity, there have to be equal numbers of spin up and spin down electrons on the superconductor side but only one spin type can get through to the chromium dioxide side. There would be an electrical traffic jam. Which is all very logical and reasonable but it isn’t what happens. Instead, for reasons that we still do not understand, not only does the electrical current get through the connection, the chromium dioxide itself becomes superconducting through its proximity to the superconductor. By itself it could never superconduct but somehow, the superconductivity is leaking¹ into the chromium dioxide at the joint between the superconducting wire and the chromium dioxide tape. And it shouldn’t do this because everything we understand about superconductivity requires there to be electron pairs of spin up and spin down and everything we understand about chromium dioxide tells us that is absolutely not the case.

So how does it work? Surely these two effects (of superconductivity and spin polarisation) are incompatible with each other? Is there something peculiar about chromium dioxide that makes it so susceptible to this strange effect? We do not yet know (though we have a few ideas). Many groups around the world are looking at this odd effect including a network of universities in the UK. It is taking us a lot of research and quite a few meetings involving coffee to work it out but hopefully one day we’ll get there.

In the meantime, it may be worth pondering just how special those cassette tapes really were.

Batch&Co is at 54 Streatham Hill Road

¹Yes, “leaking” is, perhaps surprisingly, one of the technical words for what happens in the proximity effect.

 

Categories
Coffee review General Home experiments Tea

Communities at Wilton Way

exterior of Wilton Way, Hackney Coffee
Wilton Way cafe on Wilton Way

There are two things that may strike you as you walk past Wilton Way café. The first is the prominent La Marzocco espresso machine on the counter. The second is the “ON AIR” sign in the corner next to the window. Indeed, it is best to look out for these two as there didn’t seem to be any other sign indicating that this café was the Wilton Way cafe, home to the London Fields Radio that is broadcast from here (hence the “on air” sign). In the late afternoon, the café offered some shade on a sunny day and so we popped in for a tea, though there is seating on a bench outside should you wish to enjoy the Sun. Although this website is supposed to be about coffee (which is roasted by Climpson & Sons), sometimes a fresh mint tea is what is needed. This particular mint tea was very refreshing with plenty of mint leaves in the cup. Sadly though, in what seems to be a common pattern at the moment, this was another café at which there were few cakes on offer, presumably as it was late afternoon by the time we visited. However, what is sad for the mind is perhaps good for the waistline, we’ll have to revisit in the morning for the cakes next time.

Corrugated iron supported the counter while the (plentiful) seats inside the café appeared to be made of recycled wood and boxes. Interestingly, this is mentioned in the description of the Wilton Way café on the London Fields Radio website, apparently the interior was designed to be a mix of modern and reclaimed materials. Choosing a seat at the back allowed us to survey the space and people-watch while sipping the tea. On the counter was an old-style Casio cash register while in the far corner at the front of the café, the microphone and broadcasting equipment stood waiting to be used for the London Fields Radio.

the broadcasting equipment at the WW cafe Hackney
London Fields Radio, broadcast from Wilton Way cafe

In the book “Radar, how it all began” the author, Jim Brown reminisced about how he had played with a crystal radio set as a child in the 1920s¹. Many scientists can remember making their own radio sets as children (or indeed as adults). It seems playing with things, taking them apart and building them again is part of the personal-history of many scientists and engineers (particularly experimental ones whether they be ‘professional’ scientists or not). The Lunar Society (which was active at the end of the eighteenth century and into the early nineteenth) featured a group of keen “tinkerers”. These were people who experimented with nature and invented new devices in order to explore their understanding of the world. Though each of them were only doing science ‘on the side’ as they each had other day-jobs, individuals within the group did make some important contributions to our understanding of the world. One such contribution was by Josiah Wedgwood who by observing the “waviness of flint glass” noticed its resemblance to “that which arises when water and spirit of wine are first put together before they become perfectly unified”². The reference is to mixing fluids of different density. Isn’t this experience of tinkering with things similar to our enjoyment and appreciation of coffee? The more we experiment, the more coffee we try (including cupping coffee as with this how-to from Perfect Daily Grind), the more deeply involved in coffee we become and the more we value it. Isn’t it actually true that in order to deepen our relationship with coffee we need to explore it (and experiment with it) more fully? Cannot the same be said for our relation to our world?

interior of Wilton Way cafe
The view from the corner. Spacious and quirky, the Wilton Way cafe has plenty to offer the coffee (or tea) drinker who wishes to slow down and appreciate the moment.

But then a second thought that, to some extent flows from the first. No development would be possible without a community, each contributor bringing a different talent but each contributing to an idea of a greater good. The London Fields Radio would not be possible without the scientists and engineers who design and optimise the broadcasting (and receiving) equipment. But neither would it be possible without talented DJs and musicians, thinkers, poets and performers to give us something to listen to. Two more groups of people are needed for London Fields Radio to be a success. Those who provide the space for the broadcasting equipment (i.e. the café) and those who listen in. Again there is an analogy with coffee. No cup of coffee could be there for us to enjoy without the farmers, the traders, the roasters, the baristas and finally many other people like us who enjoy a good cup. And the more each of us tinker with appreciating another’s work (cupping the coffee like a roaster or tending an allotment to appreciate the growth), the more of a community we become and the better coffee we get for it. We do not imagine while ‘cupping’ coffee that we are really about to take on the role of the coffee trader or roaster, yet by playing at their job we can appreciate their importance and skill more and so realise more effectively our own role too. We could go full-cycle here and consider how playing with radios and experiments can help us to understand the role of technology and science in society and our participation in it, but perhaps that is left as a point to ponder in another café: How can we each contribute to a better society, understand our role in it and appreciate the contributions of others?

One final thought that came from the Lunar society but appears to have a very contemporary relevance. Wedgwood once said to Richard Lovell Edgeworth “But in politics… as in religion, hardly any two people who thought at all, thought exactly alike on everything.” The main thing was “to agree to differ, to agree on impartial investigation and candid argument”.² It appears the Lunar men still have a thing or two to teach us.

Wilton Way cafe can be found at 63 Wilton Way, E8 1BG

¹Radar, How it all began, Jim Brown, Janus Publishing Ltd, 1996

²The Lunar Men, Jenny Uglow, Faber & Faber, 2003

Categories
Coffee review General Observations Science history Tea

In the loop at Coffee is my cup of tea

exterior coffee is my cup of tea, cimcot, coffee Hackney
Coffee is my cup of tea on Dalston Lane. The colour of the exterior matches the crockery used inside.

There is a lot of truth in the name of this café. “Coffee is my cup of tea” in Hackney is a lovely retreat, a place where you can take time to enjoy whatever drink is your cup of tea. Walking through the door, you are presented with a few wooden tables and a cocktail menu on the wall. A breath of calm on an otherwise busy road. Together with the bench just outside, there is plenty of seating inside. There’s even a long table along the window where you can sit if you would like to enjoy your coffee while gazing at the passers-by. There were the usual range of coffees on offer along with fresh juices, other drinks together with a range of food. When we went in the late afternoon, there didn’t seem to be many cakes on offer but maybe we were just unlucky. Coffee only this time. The coffee is roasted by Assembly and there is of course tap water available at the end of the bar.

Facing the bar, glued to the wall, were a circle of stiletto shoes. Forming what seemed to  be a “shoe star”, they were one of a number of art works around the shop. The café is also quite spacious, the window at the front providing plenty of light and contributing to the relaxed space. When my long black arrived, the light coming in from the windows produced great interference patterns on the bubbles of the coffee, an irresistible piece of coffee physics. The cocktail menu provided quite a distraction, again making the point that it was a shame we visited on an afternoon: an evening of coffee and cocktails would make a lovely night. However, a sunny afternoon was a great time to sip and enjoy a long black. While the long black started off very fruity, the taste changed (matured?) as the temperature of the coffee decreased. In the background to this all though, something so subtle as to be almost un-noticeable caught my attention. Completely surrounding the window was a very thin piece of copper wire. Were there tiny little lights on it to make the café more attractive (romantic even?) in the evening? I couldn’t see any. From our table, it seemed as if it was just a thin, closed loop of copper wire forming a loop around the window.

coffee cimcot
Fantastic interference patterns on the bubbles of the coffee at Coffee is my cup of tea

Such a loop could be used as a radio antenna, a “loop antenna”. Indeed, when Heinrich Hertz (1857-1894) first discovered radio waves in 1887-8, he used a (gapped) loop antenna as the receiver. Hertz had been trying to test James Clerk Maxwell’s theory that visible light was part of a much broader spectrum of electromagnetic waves, particularly, that there should exist very low frequency waves far beyond the visible region of the spectrum, waves that we now know as “radio waves”. Radio, TV, wifi, all things that seem so obvious now but were really only predicted and discovered relatively recently. Working in his laboratory in Karlsruhe, Hertz set up a radio generator which consisted of two brass balls that were charged until a spark flashed between them. Sitting a few metres away, a gapped loop of wire, the ‘loop antenna’ suddenly showed a spark over the gap. The spark that Hertz had generated in one part of the room had been mysteriously transmitted, as if through an aether, to be picked up by the antenna a few metres away. Clearly it was consistent with Maxwell’s predictions. The electric spark had generated a low frequency electromagnetic wave that had been picked up with the loop antenna. With further experiments, Hertz showed that this wave was indeed reflected and refracted in the same way as ordinary, visible, light and even determined its wavelength (which for Hertz’s experiment was about 66cm)¹.

loop antenna at cimcot, Dalston Lane
It is probably easiest if you visit the cafe but look very very closely at the frame of the window. There is a copper wire surrounding it.

Although Hertz did not immediately see any practical application of his result (beyond the fact that it was a test of Maxwell’s theory of light), ‘radio’ soon started to be developed. Marconi and others worked with wavelengths of 200-600 m to transmit radio waves across the Atlantic Ocean¹. As amateur radio enthusiasts got hold of radio sets in the 1920s they started working with wavelengths that were initially considered impractical for applications (much shorter than the hundreds of metres used by Marconi). These enthusiasts soon realised that they could communicate with other enthusiasts in distant countries through the reflection of the radio waves off of the (until then unknown) ionosphere¹. Gradually our understanding of radio waves and antennae design developed, leading to further, unexpected applications. Depending on the design of the antennae, radio waves (and microwaves, which have a slightly shorter wavelength of the order of 0.1-100cm*) could be made to be directional. So antennae could be made that transmitted waves only in set directions (or conversely could detect the direction from which radio/microwaves originated). This understanding of antennae design would lead to advances in Radar technology.

Which brings us back to the loop antenna at Coffee is my cup of tea. Loop antennae are grouped into two types, “small” and “large”. It is fair to say that it is a large window at Coffee is my cup of tea and so the loop antenna there would fit into the “large” category. These antenna are ‘resonant’ (meaning that they respond most) to wavelengths equal in length to the circumference of the antenna. From memory, I’d guess that the window was roughly 2m high and 3 m across, meaning it had a circumference of 10 m. We can calculate the frequency of the radio waves that would be resonant with this by using the fact that the frequency (f) is just the speed of light (c) divided by the wavelength (λ) (ie. f=c/λ). The speed of light is 3×10^8 m/s, so the frequency would be (3×10^8)/10 = 30 MHz. There are two last things to notice about this result. First, the name of Hertz lives on in the unit of frequency (Hz). Secondly, the loop antenna around the window at Coffee is my cup of tea is resonant with approximately the frequency of Citizens Band radio (CB radio operates at ~27 MHz). Which may make us question once more what this loop of wire is doing at this friendly little café on Dalston Lane.

Coffee is my cup of tea can be found at 103B Dalston Lane, E8 1NH

¹Britain’s shield radar and the defeat of the Luftwaffe, David Zimmerman, Amberley publishers (2001, 2010)

*Technically Hertz discovered microwaves rather than radio waves. However, given neither were named at the time and they are both of longer wavelength than visible light, it is perhaps too pedantic a point.

 

Categories
Coffee cup science Coffee review General Home experiments Tea

The idea of a coffee at A Wanted Man

“We cannot do without a view, and we put up with an illusion, when we cannot get at a truth“.

A wanted man, Chelsea, coffee cup
A wanted man becomes visible under thin coffee.

A Wanted Man on Chelsea’s Kings Road is unusual in many respects. Firstly, never before have I been to an espresso ‘canteen’, but then, neither have I had a coffee in a café that is part coffee-shop part waxing salon. While both wax based hair removal and coffee rely on bees, this is surely not the connection between these two enterprises. Nonetheless, once your coffee-loyalty card is full, you can choose: free brow shape, bikini wax or coffee. The coffee comes from Common Man Coffee Roasters in Singapore so it would be interesting to know how it was transported to Chelsea in order to retain its freshness, surely each batch is not flown in? On our first visit, we had a rich and smooth long black, a lovely aromatic banana bread and a good hot chocolate (with soy milk). There is plenty of seating in the front of the café and some more towards the back near the bar which was all fairly empty on our first visit but far more crowded (with singly-occupied tables) on my second visit (see below).

As I drank my coffee, hidden wording became visible at the bottom of the cup. “A wanted man” appeared beneath the coffee when the coffee was sufficiently thin. By tilting the cup, this “critical” thickness could be estimated, as you can see in the photos. Ah-ha I thought, the physics bit of this cafe-physics-review will be easy! The absorption of light (which we could measure by the visibility of the writing at the bottom of the cup) is directly proportional to the thickness of the absorbing liquid, the coffee. This is the Beer-Lambert law which describes how light is absorbed through substances such as coffee in which there are molecules and bits of sediment that absorb light (which is ultimately why coffee appears brown). Could I experimentally verify this bit of the Beer-Lambert law by somehow quantifying the visibility of the wording as a function of cup-tilt angle?

a tilted coffee cup at a wanted man
Absorption is a function of thickness and concentration

Before I had thought that far, I had finished the coffee, however the second part of the Beer-Lambert law could be tested by having another coffee on a separate occasion. The other part of the Beer-Lambert law states that the absorption (that’s the (in)visibility of the wording on the cup in this case) is also directly proportional to the concentration of the absorbing molecules/sediment. This makes sense, weak coffee is far more transparent than overly extracted coffee. On my second visit, the coffee tasted slightly stronger, a bit different from my memories of the first occasion. Did the “A wanted man” become visible at a different tilt angle? I would guess – or perhaps that should read ‘hypothes-ise’ – that the angle on the second occasion would have to be lower (that the coffee would have to be thinner generally).

However, while sipping my coffee (before getting to the tilt-angle-test) and looking around the second time I noticed that all along the wall where previously there had been plenty of empty tables, each one was now singly occupied by somebody using a laptop, a phone/tablet or in one case, both of these items together. This second time, my mind started wandering into more social issues, while looking at our screens and immersed in social media, are we able to see more or less, than our less absorbed fellow citizens? Does social media clarify the detail or cloud important aspects of our understanding?

Beer-Lambert applied to twitter and Facebook
Does social media do this to you? The light absorption of a coffee is determined by the thickness of the coffee and concentration of absorption sites within it.

After considering these two points, it became clear that in some ways they are connected. Admittedly a loose connection, and not one that is strictly scientific but perhaps it’s worth ‘running with it’ for a bit and seeing if it leads anywhere. Just as with the Beer-Lambert law with coffee, the more ‘interacting sites’ (or absorption sites) we encounter on social media, the harder it is to see through to the bottom. Twitter, Facebook etc. can be enormously helpful for widening our networks and learning about new things. But, as has been frequently pointed out elsewhere, they can also become quite unhelpful when we are in an “echo chamber” or when we think that points can be made in mere soundbites. Is it possible that the more absorbing and reflecting sites that we encounter, the harder it is to see anything to any greater depth? What we need is time-out, for self-reflection and for considering points made by others, on Twitter, Facebook and elsewhere.

Perhaps the best way to end such a post is with a long quote by somebody else. In fact, the same person (and in the same book) as was quoted at the beginning of this article. Perhaps it would be something to consider while we drink our coffees and hover over the ‘retweet’ or ‘share’ button. Are we helping to probe the depths of our cup by the links we share, or are we merely adding to absorption sites in soundbites in our networks?

“It requires a great deal of reading, or a wide range of information, to warrant us in putting forth our opinions on any serious subject; and without such learning the most original mind may be able indeed to dazzle, to amuse, to refute, to perplex, but not to come to any useful result or any trustworthy conclusion. There are indeed persons who profess a different view of the matter, and even act upon it. Every now and then you will find a person of vigorous or fertile mind, who relies upon his own resources, despises all former authors, and gives the world, with the utmost fearlessness, his views upon religion, or history, or any other popular subject. And his works may sell for a while; he may get a name in  his day; but this will be all. His readers are sure to find on the long run that his doctrines are mere theories, and not the expression of facts, that they are chaff instead of bread, and then his popularity drops as suddenly as it rose.“

John Henry Newman, The idea of a university.

A Wanted Man can be found at 330 Kings Road, London

Categories
Coffee cup science Coffee review Observations Science history Tea

Coffee innovations at MacIntyre, Angel

MacIntyre Coffee AngelOne motivation behind Bean Thinking is to explore those connections that can be found when we stop to really look around us. Whether your interest is in history, philosophy or science, something in a café will prompt a train of reflections that can lead to interesting and surprising thought journeys. This is surely true for anybody in any café, if we just take the time to slow down. But, I admit a prejudice: while I had heard great things about the coffee in MacIntyre, when I had glanced in from the bus window, I saw the scaffolding seating arrangements and wooden surfaces that can be a type of design found in many new cafés. So I worried. Was it going to be hard to ‘see the connections’ in MacIntyre? Would I end up with a great coffee but a challenge to my assumptions about the ubiquity of connectivity?

Fortunately, I needn’t have worried. The two lovely coffees that I have enjoyed at MacIntyre gave me plenty of time to really savour both the coffee and my surroundings and I was wrong in my assumptions from the bus window, connections really are everywhere. The café itself was a delightful find. Watching other customers while drinking my long black, it seemed that everyone was greeted by a cheery “hello”. Many people were clearly regulars, which is perhaps unsurprising for a friendly café with good coffee in a busy area. The scaffolding and wooden seating also works in the space at MacIntyre, giving a strangely relaxing feel to the café. The café itself is rather narrow, with the seating on one side and pastries/ordering queue on the other. Tap water was delivered with the coffee, without my needing to have asked for it.

Plant, light, scaffolding at McIntyre's Angel
Good scaffolding also has good connections.
Plant and light at MacIntyre.

MacIntyre may also be a great spot if you are into people watching. Amidst the general busy-ness, I could eavesdrop on conversations about the latest coffee news and the rise of artificial intelligence (these were two separate conversations!). Perhaps the conversations were particularly noticeable owing to the acoustics of the wooden walls and the narrow, small space of the café. At various points around the café, plants hung from the scaffolding. Some of the plants were spot-lit, which caused me to wonder whether the light that the plants were receiving was optimal for photosynthesis. The menu was projected onto the rear wall of the café, which was also decorated with hexagons, an immediate connection to graphene.

But then, in my coffee cup, the significant crema on the coffee showed evidence of amazing thermal convective motion together with turbulence. The coffee itself was very sweet with nutty overtones but the movements of the crema reminded me of cloud formation in thunderstorms. Although thunderstorms didn’t make it to the thought train of MacIntyre, another form of surface motion suggested a connection to another, unusual, feature of this café. You see, MacIntyre is a cashless business, no cash is accepted even if you’re only buying a long black. Most customers on my visit paid with their contactless cards.

The idea of a cashless society is one that has obvious advantages for both the business and the government/economy (whether it has such obvious advantages for the consumer I will leave as a point to be debated). While some countries are attempting to move to a more cashless economy, for a business to be entirely cashless is somewhat innovative. Even though MacIntyre is not the only café to go cashless (Browns of Brockley is similarly cash free), it has to be one of the first cafés to do so.

Coffee at MacIntyre Angel
Coffee and water on wood at MacIntyre Coffee. Could you increase the returns on your investments by understanding the movements on the surface of a cup of coffee?

What is the connection between this and the surface movement on my coffee? Well, it is not just at MacIntyre that a café has supported an innovation that has (or may) change our economy. Just over three hundred years ago, Jonathan’s Coffee House in Exchange Alley was a place of similar innovation, though there it was a customer rather than the coffee house itself that gave the change.

It was at Jonathan’s in 1698 that John Castaing published a paper twice a week detailing the latest stock prices titled “The course of the exchange and other things”. Recognised now as the origin of the London Stock Exchange, how stocks are priced and how their prices vary with time are subject to intense mathematical modelling. Although now, these models can be extraordinarily complex, the base of many of them share a mathematical model with the movements on the surface of your coffee cup, Brownian Motion.

Jonathan's coffee house plaque
The site of Jonathan’s in Exchange Alley. Seen while on a Coffee House tour last year.

Brownian motion is the phenomenon in which small particles of dust, or coffee grains on the surface of your coffee move in a random way as a result of collisions between the particles and the molecules in the liquid. First described in detail by a botanist, Robert Brown in 1827, the experimental evidence in favour of the molecular-collision explanation of Brownian motion came in 1910 with Jean Perrin’s careful experiments (that have featured in The Daily Grind previously). The maths behind the explanation relies on the idea of the ‘random walk‘ in which each dust particle is ‘kicked’ in a random direction by the molecules in the coffee, the consequent motion being frequently described with reference to a drunkard attempting to get home after leaving the pub. However, as this concept of the ‘random walk’ was being developed for molecules in a liquid, it was simultaneously being developed to model the movements of stock prices by the mathematician Louis Bachelier. Bachelier’s model of stock prices turned out to be the same as the model of Brownian motion, but both developed independently.

As yet, it is unclear (to me at least) whether there is a link between cashless payments and some of the maths in your coffee cup but, MacIntyre would be a great place to contemplate this as you sip your brew. Never succumb to prejudices, on which note please do let me know what you think of cashless payments, a great convenience or an invasion of privacy?

MacIntyre can be found at 428 St John St, EC1V 4NJ.