The interdependence of science and (latte?) art

latte art, hot chocolate art, soya art, albedo, science and art mixing
The difference in contrast between the art on a cafe latte and a hot chocolate is revealing of a lot more than just a tulip.

In Paradiso, Canto II, Dante asks Beatrice about the Moon: “what are the dark marks on this planet’s body that there below, on earth, have made men tell the tale of Cain?”*

On Earth below, it is perhaps the brightness of the milk in the latte art that we notice in our coffee. But it is in fact precisely the contrast that we notice, both on the Moon and in our coffee.

What causes this contrast in the coffee and how does it link back to the Moon? Watching videos of, or if you are lucky to be close enough, baristas making latte art, you may be struck by the skill of the barista to form the milk into complex patterns and art. Swans, tulips and other designs appear on the surface of the drink with seemingly simple oscillations of the hand. And yet, if you’ve ever thought about attempting this art, you will appreciate how hard it is to design this contrast. How does the first pour of the milk lead to a significant uptake of the coffee (and hence a brown colouring), while the second part of the pour is dominated only by the milk and hence the shapes appear?

It must be partly a turbulence effect. The initial milk pour is from a significant height which would churn up the coffee meaning that the suspended particles in the coffee then get caught in the spaces between the bubbles in the milk’s microfoam. The second part of the pour is from a lower height which leads to a reduced mixing between the two liquids.

Brew&Bread, latte art Sun, KL latte art
Complicated patterns are revealed by the difference in colour between the coffee and the pattern.

Yet this is only part of the story. Another perspective on it could be to consider the ‘albedo’ of the drink. The albedo is a measure of how reflective a surface is, so highly reflective surfaces (milk bubbles, ice sheets) have a higher albedo and less reflective surfaces (the coffee liquid, the earth’s surface) have a lower albedo. Part of the visibility of the latte art comes from this difference in reflectivity between the pattern part and the base part of the coffee.

In Earth science this has consequences for climate change: if the ice (high albedo, highly reflective) melts and reveals earth or sea (lower reflectivity, lower albedo), more sunlight is absorbed by the Earth and consequently you get local heating and locally accelerated ice melting. This may have consequences more globally in terms of climate change.

For Dante, it explained the colouration of the Moon. As his guide Beatrice explained to him: different parts of the Moon shone differently depending on their composition**.

Another example of latte art. Science meets art meets the skill of the person producing it.

Which takes us to another connection between science and art. It is recognised that, in European science history at least, Galileo first realised that the ‘dark marks’ on the Moon’s surface indicated that there were mountains and craters on the Moon. He was able to do this because he saw the Moon through a telescope and deduced that the patches were shadows. But when we think about this, it can’t be the whole story. While a telescope magnifies a distant object we still see, effectively, a 2D surface. We see the mountains on the Moon in the shadows because we know they are there. But how did Galileo know? Indeed, another astronomer at the same time was looking at the Moon through a telescope and could deduce only “strange spottedness”. What was the difference between Galileo and Thomas Harriot that allowed the former to see what the latter could not?

It has been suggested that it was Galileo’s artistic training that meant that he recognised the shades of light and dark as shadowsª. His practise at chiaroscuro drawing meant that he knew how to render depth using light and darkness in 2D images. When he saw the Moon, he could recognise the mountains. Another scientist, not familiar with how to render depth in painting, may instead see latte art on the Moon.

There are many ways in which our different backgrounds benefit each other and in which it benefits us to work as teams rather than individuals. There remain some though where the right combination of knowledge of both art and science combined with a particular skill at rendering them, can result in brilliant coffees, or astonishing discoveries, through connecting dots that otherwise could not be seen.

*The Divine Comedy, Dante Alighieri, Paradiso, Canto II. It is interesting here that Dante uses the word “planet” for the Moon, something that we would not do now. In a way it emphasises how our descriptive language changes with time and therefore how there may still be hope for Pluto’s rehabilitation.

** It is interesting here though that Beatrice’s answer to Dante is given to him only after she has convinced him through two experiments that his own explanation for the patches of the Moon was wrong.

ª Styles of Knowing, Chunglin Kwa, Pittsburgh Press, 2011

Journeying with coffee

Always plenty to notice while brewing coffee

A short while back while preparing a V60 and watching the coffee level slowly rise to “4 cups” (just about what is needed in the morning for one person I think), I started wondering about rain gauges and how we measure the rainfall. While the first rain gauge was recorded in India in the 4th Century BCE, their design was still being optimised well into the 20th Century. We clearly need to know and agree how to measure rainfall, not just for agricultural reasons, but also for our understanding of the climate. But, more fundamentally, being able to measure quantities precisely and accurately, as well as being able to agree on what we measure seem to be fundamental to any advancements in science. We are perhaps struck by the number of people who have contributed to our knowledge of the world, either directly or indeed indirectly through getting it ‘wrong’. How many times have wrong ideas contributed to an advance in, what we consider at the moment to be, the right ideas?

And then there is the kettle that you may have boiled to prepare the coffee. Hidden by familiarity, the bimetallic switch that ensures that the kettle turns off as the water boils is a fairly recent invention. While the development of our understanding of the perfect brewing temperature for coffee is a mixture of the work of the coffee professionals and the development of the thermometer, itself a journey into science and philosophy.

kettle, V60, spout, pourover, v60 preparation

An over-looked item? It can be instructive to consider how many people have worked to optimise this ‘ordinary’ kitchen object.

Indeed, when we consider the number of people who have contributed to our ability to enjoy our morning coffee it is striking. From the roaster to the farmer, the trader to the inventor: pausing to consider these things may perhaps emphasise to us our dependence on (and growth in) society rather than our individuality.  But then, if we extend our thoughts to the insects and agriculture that enable the coffee plants to thrive, we may come to an awareness of our dependence on the planet; a recognition that “we are profoundly united with every creature….”¹ Does this awareness have an influence on how we behave in and as a society?

In “Styles of Knowing”, Chunglin Kwa argued that just as the forms and styles of painting are responses to the social circumstances, so are styles of knowing². He argued that:

Earth from space, South America, coffee

How do our attitudes affect the science we do, and our perception of the coffee we drink?
The Blue Marble, Credit, NASA: Image created by Reto Stockli with the help of Alan Nelson, under the leadership of Fritz Hasler

“[The humanists] strong emphasis on the vita activa [rather than the vita contemplativa] probably contributed to a scientific mentality aimed at sweeping aside obstacles, making decisions, and then taking action, rather than focussing on consensus, like the medieval scholastics. For humanists, it was the will that mattered.”

It seems that in our society as we encounter ever more distractions, there are always more ways for us to believe that we are busy and therefore useful. Does our embracing of this ‘busy life’ contribute to some of the issues that we define as problems? Do we gain control over some of the issues by taking responsibility for parts of them rather than avoiding them? What would happen if we stopped to contemplate our world, maybe just for 30 minutes each day? We could even do it while we journey into the world revealed by our coffee mug. Would it affect the way that we do science, think about society or drink our coffee?

There is a great deal of depth in a cup of coffee. Four cups is not enough. Do let me know where your mind wanders.

¹Laudato Si’, Pope Francis, 2015

²Styles of Knowing: a new history of science from ancient times other present, Chunglin Kwa, University of Pittsburgh Press, 2011

Details at The Italian Coffee Club, Shepherd’s Bush Market

Italian coffee club, Shepherd's Bush Market
The Italian Coffee Club. Plenty of chairs both inside and out.

What’s in a name? A hundred impressions and assumptions, an idea that to know somebody is to know their name? And so it was that The Italian Coffee Club thew me. Towards the Uxbridge Road end of Shepherd’s Bush Market, The Italian Coffee Club is in a wooden lined chalet. A few tables outside and some prominent signage leave you in no doubt as to the fact that coffee is served here. A sign asks if you would like to try the signature Italian blend, while another informs you that the aroma of the coffee “comes from here”.

Which goes part the way to explain why I was surprised when I walked in. Inside, a number of chairs and tables line the, fairly narrow, space leading to the counter. Towards the counter are various large jars of freshly roasted coffee beans ready for retail. Perhaps this should have given me a clue to check my assumptions. The roasts were varied with a good choice of origins, including several single origin. The coffee menu offered the usual choices and…. V60s of any of the various coffees that they sold (sadly I noticed this only after I had ordered an Americano). The coffees are roasted by The Italian Coffee company and include several direct-trade relationships. Although I had the “signature” Italian blend on the day, I did purchase 200g of the La Abuela washed Colombian to take home with me as beans. La Abuela means grandmother and apparently this coffee farm (which is one of those with which The Italian Coffee club has a direct trade relationship) is run by an 80 year old lady growing coffee that scores 83+ in the speciality quality score.

The aroma of coffee comes from here, The Italian Coffee Club, Shepherd's Bush
There were several signs about the aroma of coffee. This was one of them outside the cafe.

Looking around this chalet/cafe, the first thing that caught my attention was a sign about “smelling the aroma”. This immediately conjured up thoughts as to how it is that we actually perceive smells. In some ways an incredibly basic sense, in others, something that we still do not understand. It also prompted me to think about anosmia (smell blindness) and its allegorical relevance to my assumptions as I had entered the cafe about the coffee I would find.

The jars of coffee were the sort of transparent bottle with a rubber seal, reminiscent of vacuum physics. A (presumably decorative) manual coffee grinder at the bottom of the shelves could have prompted thought trains about automation and whether the coffee making process is improved by the uniformity of grind obtained by industrial grinders or the imperfections (but connections) that we would have through a fully manual brew (I think it may depend on what we mean by ‘improve’).

And then I looked down at my coffee and noticed a hair floating on top of it. I knew it was mine because it hadn’t been there originally and it was of the right length and colour. But I could tell it was there due to the indentations on the liquid surface around the hair, much as you can see the indentations around the feet of a pond skater. How much force was the hair exerting on the surface of the coffee to make such indentations? And when would it ‘fall through’?

Hair, surface tension, coffee
I wasn’t worried: it was definitely mine! But look at the way the surface of the coffee is affected by the hair. Why does it bend in such a way?

The surface tension of the coffee is caused by the water molecules in the liquid being attracted by the other water molecules into the coffee but not having anything above the surface to balance that force. Consequently, there is a net attraction for the molecules at the surface into the coffee and a ‘skin’ is formed on the surface, rather like an elastic sheet. This ‘skin’ takes a certain force to break it, which can be measured and which is called the ‘surface tension’. My hair, about 5cm long, as a typical human hair, weighs about 168 micrograms. Which means the gravitational force acting on it is F = mass x gravitational acceleration = 1.68 microNewtons. Expressed as a Force per unit length, this works out as 34 microNewtons per meter. In comparison, at 60 C, the surface of water requires a force of Newtons per meter to break through it. My hair would be no match: the surface tension supports the hair.

What about a pond skater? That has a slightly larger mass (at 0.02 g) and it is also slightly shorter (20 mm), so its force per unit length is also larger at 0.01 Newtons per meter. So although it is going to push down more on the surface of a pond (or my coffee) than my hair is, it still won’t break the surface.

cat in Shepherd's Bush Market
It’s the little things….

As this is a coffee blog, what if we took the example of a coffee bean and, neglecting for one minute any other considerations, calculated the force it exerts on the water/coffee. Beethoven’s 60 beans of coffee had a mass of 9 g. So one bean has, roughly, a mass of 0.15 g. Each bean is about 1cm long and so it exerts 0.15 Newtons per meter on the water surface. Certainly enough to break it: so we could use coffee beans to measure surface tension. A novel purpose for the coffee bean, but I prefer my more traditional approach of grinding and drinking it.

Which took me back to the Colombian, La Abuela that I purchased from The Italian Coffee Club and tried, at home, as a V60. Sweet and syrupy, with cherry fruit: an enjoyable coffee for some time to ponder.

The Italian Coffee Club can be found in Shepherd’s Bush Market, Shepherd’s Bush.

Cracking pour overs

cracks in a wheat field
Cracks in the soil in a field after a dry spell. But there are many connections between coffee and soil.

Summer this year has so far been quite hot and dry. Perhaps you have seen the grass dying back. Or maybe you have noticed the cracks forming in the soil in your local parks and fields. Such cracking is the result of the very dry weather and hopefully you won’t find it in your coffee, but there is another effect concerning soil compaction that connects to brewing a morning coffee as well as farming it.

It’s about the rain. As each raindrop falls to the Earth, it makes an impact with the soil underneath. While a light drizzle is not going to have that much of an impact, a larger raindrop of diameter say, 5mm, is going to hit the earth at about 9m/s – and that could cause quite a stir. Each impact will shake off smaller sized particles of soil which dislodge and get stuck in the pores between the larger soil particles. So the smaller particles start to ‘clog’ the pores between the soil particles and reduce the ability of water to penetrate into the soil. And although it seems a small effect, the result of this clogging of the pores by the smaller soil particles is to reduce the water permeability of the soil by 200-2000 times*: a soil crust is formed.

lilies on water, rain on a pond, droplets
The impact of a drop? Each rain drop can have a significant effect on the soil surface

This crust not only reduces the amount of water that gets through to the roots (by reducing the soil’s permeability), it also acts as a barrier for seedlings coming up: while many seeds can get through quite strong layers, even Sorghum struggles to push through if it needs pressures of 13-18 Bar to break through this crust*. So even without any farming machinery causing further soil compaction, just the rain is going to affect how additional water goes through the soil and how plants can grow out of it.

We are getting to the coffee bit.

The crust strength is influenced by the number of small (clay-type) particles in the soil. Clay particles are less than 2 microns in diameter which is smaller than the grind size you would find in even a Turkish coffee grind. But if we were to grind very brittle coffee beans (that shattered into many smaller particles as well as the grind size we want), or we were to use a blade grinder leading to a large distribution of grind size in our freshly ground coffee, we may expect to see some effects like this while brewing.

optical microscope image in water
Two coffee grinds compared under a microscope. How does the uniformity of particle size in a grind affect the clogging of a pour over? Magnfied 5x

If we think about a pour over brew (as opposed to an espresso or an immersion type), the initial pouring of water over the grind bed will dislodge any smaller particles in the grind and clog the grind in the same way as the rain on the soil. So if we were grinding way too fine, or using a blade grinder, or had a preference for darkly roasted (more brittle) coffee beans, it is possible that our pour-overs would tend to ‘clog’ more than if we were using a uniform medium grind of more lightly roasted beans. Has anyone experimented with this?

But the second soil connection we may notice as we prepare our pour over is that after our initial pour, as we let the coffee ‘bloom’ and the CO2 bubbles out, we receive a lovely aroma. A wonderful coffee smell as the grind bed continues to out-gas. This may remind us of petrichor, which is that great, and distinctive, smell of rain. And it turns out that petrichor is formed by the rain hitting the soil surface and producing air bubbles as it falls. The air bubbles then burst releasing aerosols from the soil which are so familiar to us as the scent of rain. A similar process to the blooming of the coffee grind. But just as with the coffee grind, as the water continues to fall and particularly if the pour over clogs to leave us with a water layer on the surface of the coffee (or soil), the aroma will reduce (or at least change) as the mechanism producing the smell changes.

bloom on a v60
Blooming petrichor, or should it be coffichor?

On a farm or in a garden, the effect of this soil compaction can be reduced by practises such as mulching. In addition to reducing the impact of individual rain drops on the soil surface, the mulch reduces evaporation of the water from the surface and changes the albedo of the soil. All things that may help coffee farmers to grow healthier coffee plants. In our pour overs, it is probably not a good idea to add any form of mulch! But this does mean that we can experiment more with the grind!

There are many more connections between your coffee and the earth around us, what will you notice?

*Soil Physics, WA Jury and R Horton, Wiley and Sons Publishing, 2004

Good vibrations at Rosslyn, Mansion House

Coffee at Rosslyn, Mansion House, EC4N, coffee clock, base
Coffee time at Rosslyn, EC4N. Why is it that base 60 was used as a counting system in Mesopotamia? And why is it that the echoes of this are still seen in our clocks and the angles of a circle (unless you use the radian system) but not in our everyday counting system?

It’s always “coffee time” at Rosslyn apparently, at least according to the clock above the door. In front of you as you enter the cafe is the counter and, as you move down to collect your coffee (for take-away) the day’s edition of the Financial Times is stuck to the notice board where you wait. An interesting touch, somehow making a resonant connection with the City coffee houses of old such as Jonathan’s, just around the corner, where the stock market was originally located.

There are not many stools or tables in Rosslyn, which appears to be designed as more of a take away space. Nonetheless, we found a perch by the window overlooking the bench seats outside. It is a perfect place to watch the world go by. The massive junction of Poultry providing plenty to see.

Coffee is roasted by Modern Standard and there are bags of roasted coffee on sale (together with some of the mugs) at the other end of the counter to the FT. The occasional (welcome) plant reminds us that life is not just concrete, glass and cars/buses. Although it was sunny, it was not yet hot and so we had a soy hot chocolate and a long black, went back to take our seats and waited for the drinks to arrive.

The wooden spoon that came with the coffee was an interesting touch, reminding me of Barn the Spoon and his work in Hackney. While the clock got me thinking about our use of base 10 as a counting system and the older systems that used base 60.

coffee, hot chocolate, plant, mugs, wooden spoon.
A quiet moment with a coffee and a hot chocolate at Rosslyn. Notice the spoon.

Contemplating these things we noticed a strange effect in my coffee. Or rather, I noticed it and brought attention to it by taking repeated photographs of the coffee while tapping the bench just to try to capture what I was seeing: a resonance pattern on the coffee surface. At this point, your mind may connect to several different things. There’s the resonance effects involved in the Whispering Gallery in St Pauls close by to Rosslyn. There are the resonance patterns caused in bells, drums and violins and the relation between these, air movement and music. There’s the fact that these movements initially revealed the excellence of the table as a movement sensor: the ripples on the coffee revealing footsteps behind us rather like we detect earthquakes in the earth. (My later attempts at photographs were in that sense “faked” as I was tapping the table beside the cup to try to reproduce the effect so that it was visible on my camera).

Or there was the fact that this movement in the coffee cup is exactly the same phenomenon as something in our lab. But whereas in the cup it is an interesting, almost aesthetic feature, in the lab it can be a major pain to deal with.

The problem comes in that the coffee cup was in the middle of the bench. This had been an accident in terms of where we were seated but it had large effects. Because the bench table has its legs at each end, but nothing in the middle, the table itself acts as if it is a massive drum. And one of the more fundamental resonances of a drum has the maximum movement at the centre of the drum: the edges don’t move much but that bit in the middle oscillates wildly. In the coffee cup this manifests as a ripple pattern on the coffee surface, reflecting the street outside in slightly distorted fashion. In the lab this means that some of our instruments become incredibly difficult to use.

ripple pattern coffee Rosslyn
Can you see it? The ripple pattern caused by the coffee being on the drum of the table at Rosslyn. An interesting effect to watch in coffee but what if this sort of thing happens in a physics lab?

Consider for example the Atomic Force Microscope (AFM). This microscope is able to resolve the structure of films down to an almost atomic resolution. It does this by monitoring the resonance of a small silicon cantilever as it approaches the surface of the material being studied. Just for a moment, put a wooden sugar stirring stick (or a lollipop stick) on the edge of a table and ‘twang’ it. It vibrates just as the silicon cantilever does in the AFM. Then think, what if you put the stick in honey and ‘twanged’ it – or put a magnet on the end of it and ‘twanged’ it over a bit of iron, how would the oscillation change? This is what the AFM does but with the atomic forces that are present when you get very close to the surface of a sample. But the phrase “very close” is key. Typically, the cantilever will be nanometers from the surface of the sample and, as it is very sensitive to the forces at the surface of the sample, if that sample moves because the instrument is vibrating up and down on the floor, the image will be at best blurry and unusable and at worst, you are going to be damaging your cantilevers.

And so, it is important to ensure that the AFM is placed in a suitable area of the lab: not in the middle of a floor in a high level building because that will just act as a drum in exactly the same way as the coffee cup was being vibrated at Rosslyn. If you’re not fortunate enough to have the AFM in a basement lab, you could place the AFM (and other vibration sensitive instruments) at the corner of the room, so the vibration amplitude of the floor-drum is minimised. You could also try to place the instrument on concrete blocks to ‘damp’ the vibration. An extreme example of this sort of damping is the ‘quiet labs’ of Lancaster University just next to the M6 motorway. These labs have been designed to minimise vibration noise and the team there routinely achieve atomic level resolution with their atomic force microscopes.

The silence of an area next to the M6 contrasting with the noise of the City. The directions that contemplating a cup of coffee takes you are always surprising.

Rosslyn is at 78 Queen Victoria Street, EC4N 4SJ

A first coffee & science evening at Amoret

intro board for Amoret evening
An evening of coffee and science at Amoret Coffee in Notting Hill

A couple of weeks ago we hosted a first “coffee and science” evening at Amoret Coffee in Notting Hill. Designed to explore a physics concept that you could notice in your coffee cup with people from a diverse range of backgrounds, in some ways, the evening itself was an experiment. Would anyone turn up? Would the experiments be interesting? Was I just making my coffee badly?

This last question referred to the fact that the connection for that particular evening had been the dancing drops that skirt across the surface of a V60 (or other pour over) as you prepare your coffee. I had noticed these a couple of years ago but at that point had not appreciated their significance. To answer that question, we were prepared two excellent pour overs by people who really knew what they were doing. And we were spoiled for the coffee which was a recently roasted Nicaraguan washed coffee grown by the Baltodano family who also came along for the evening. The two pour overs were prepared very slightly differently and produced drinks that highlighted different aspects of the flavour of the coffee (though sadly I only managed to try one). This led to a fair amount of discussion amongst those present, not just about which they preferred, but how the preparation affected and highlighted different flavour notes.

Pour overs at Amoret
Preparing pour overs by two (slightly) different techniques. But would we see the dancing drops? (Yes x 2)

The pour overs showed that the dancing drops were there (in both techniques) when coffee was made properly. This was a relief for me! But did they also supply a clue as to how these drops were able to survive, as liquid drops, on the surface of the coffee?

Ordinarily, when a drop drips into a bath of liquid, you would expect it to quickly coalesce with the liquid bath. Once the drop gets close enough to the surface, the van der Waals forces in the drop and the liquid bath will overcome the surface tension effects and the drop will be subsumed into the liquid. If the drop does not coalesce, but instead appears to ‘float’ on the surface there must be a reason.

The first reason that the drop may survive for a while on the surface is because there is a temperature difference between the drop and the bath. This sets up stresses within the drop that pull air into the region between the drop and the bath and keep the drop ‘floating’ for a little while.

Secondly, if you increase the surface elasticity of the droplet, you can stabilise it on the liquid bath for longer. This is usually done by adding soap to the water, not something we did with the V60. But could there be an effect of the coffee oils or some other aspect of coffee chemistry that is keeping these droplets afloat?

Experiments at Amoret
You can see a drop almost ‘sitting’ on the surface of the water here (circled). This particular drop was stabilised for about 15 minutes. I think if you look carefully you can see a ripple pattern around the droplet in addition to the standing wave pattern on the surface of the water caused by the loud speaker underneath (indicated by the red arrow).

Lastly, if you vibrate the surface of the liquid bath, you can create conditions whereby the droplet ‘bounces’ on a cushion of air on the bath. It was interesting, that in the preparation of both pour overs at Amoret that evening, the times that we observed the dancing drops coincided with those times that the pour over was dripping into the coffee bath, causing a noticeable ripple on the surface.

This last condition was the subject of an experiment in the corner of the upper room at Amoret where we used a loud speaker to generate vibrations to two different liquid baths (water and soap water for example) to see if we could obtain stable drops on the surface. Astonishingly, some of the participants on that Tuesday managed to keep a droplet stable for about 15 minutes, you can see their droplet in the photo. The photo is interesting because if you look closely, not only can you see the wave on the bath of water caused by the vibration of the speaker, but you can also see a circular ripple pattern around the droplet. Is that the ripple caused by the droplet’s bounce?

Conversations led on to the fact that these drops were not just seen in pour overs but could occasionally be seen in espressos too. I’m definitely looking forward to the video of that one. While we also got to discuss the importance of different parameters on the stability of the drops – it turns out droplet diameter, as well as the forcing amplitude (which translates to, how loud you have the volume on the loud speakers) are key parameters that affect the behaviour of the drop, something that has been pointed out elsewhere.

V60 droplet floating bouncing sitting on coffee
A drop in-situ

The evening also emphasised just how much we have to talk to each other about! One topic that kept coming up was fermentation, specifically with how the coffee cherries are processed. Hopefully this could become the subject of a future conversation.

Future events are planned (in theory but not yet in practise) and so if you’d like to make sure you hear about them, you can sign up to the Bean Thinking events list here. Also, if you didn’t get chance to take part in the evening but would like to continue the discussion and maybe add your videos & comments about the droplets, you can sign up to the Virtual Coffee House which will be discussing this topic (until the next coffee & science evening).

Digital information at Kape and Pan, St Giles

coffee Kape and Pan
My pour over coffee at Kape and Pan.

The area around St Giles has changed significantly in recent years. As old haunts have disappeared, new ones spring up in that regenerative evolution that seems to characterise parts of London. Kape and Pan is in the foyer of one of these new buildings (that apparently also homes Google). In some ways it is very much in tune with the new buildings surrounding it and yet there are a number of touches if you take the time to sit and wait attentively for your coffee to arrive (and more that I discovered on researching the cafe later). I was alerted to the opening of Kape and Pan by its mention in Caffeine Magazine and, as I was in the area, it seemed an opportune moment to try it (once I had found which of the glass buildings was number 1, this does not seem to be an area where an address helps!).

Some interestingly titled non-coffee drinks shared the menu with the usual combination of espresso based drinks. Kape and Pan focus on coffees from South East Asia and edibles that are influenced by the flavours of that region. Three coffees were highlighted for the pour over menu. The ‘house’ coffee from Myanmar, an Ethiopian and one that I didn’t make a note of (but as these last two are on rotation, it will have changed by the time you try it). I ordered an Ethiopian pour over, with notes of peach and tea, found a table, and then waited for my coffee.

Light was pouring through the glass windows of the front of the building and so I sat towards the back of the space, with a good view of the pour over being made. That day, a technical problem had meant that payment was by cash only and watching each new customer arrive and encounter this problem, it was great to watch the relationships that had already built among regulars and the baristas and how that contributed to solving it in each case. It is interesting to see how new places develop a sense of community.

Clearly not stainless steel. Does the spoon affect the taste of the coffee? (Answer: yes it can and it has a chemical basis but you have to be drinking your coffee from your spoon)

One of the themes of the cafe appears to be a coffee drinking Buddha. Coffee in one hand, something to eat in the other, he is clearly enjoying his coffee while he contemplates it. And perhaps you may have imagined that the ‘digital’ referred to in the title would be connected with the fact that Kape and Pan is in a Google building, with associated physics connections of data processing and analysis, AI, etc. But no. The digital information comes from the representation of this sage.

As I enjoyed my (definitely tea like, though I did not ‘get’ peach) pour over, my non-coffee drinking companion studied the sugar jar. And gazing at the Buddha’s hand, commented about the perspective that the artist had taken of the fingers and then considered the evolution of the fully opposable thumb in tool use. This is a connection that would not have occurred to me as I don’t spend time drawing and emphasised the importance of listening to the experience of others (something that also was apparent in the evening of coffee & science held at Amoret on 11th June, more details about how this went next week).

It turns out that our idea of the evolution of the thumb and the human hand is still a debated issue and the story of our understanding is, in some ways, an interesting illustration of how science is done, together with the human prejudices and ideas that go together with that.

The idea had been that humans had split from our ape relatives fairly early on in the evolutionary time scale. And that, after that point, we had developed thumb use and other advantages that allowed us to develop tools and to become, as a species, fairly successful. But a spanner in the works came in the 1980s and 1990s when biologists were able to show by looking at the DNA of living primates, that humans were actually a lot closer to the chimpanzee than had been realised. So the model was adapted, humans and chimpanzees had a common ancestor but then the human hand structure evolved a longer thumb relative to the chimpanzees and so we acquired tool use etc. So far, so easy but how can we be more quantitative?

Buddha Kape and Pan coffee drinking
Happy coffee drinking contemplation.

The relative length of the thumb of a primate can be quantified by measuring the length of the thumb (down to the base of the hand) compared with that of the ring finger. Humans have a ratio of thumb length to ring finger length of about 0.75 compared with about 0.35-0.6 in other living apes (I challenge you not to measure yours!). And it is here that there is an issue when people look at the fossil record. There we find ratios that are similar to that of modern humans suggesting that while human hands differ significantly from currently living apes, our hands are not so different from some primates that lived long ago. This would mean that our hand evolution was not there for our specific evolutionary advantage.

But there is more, even the phrasing of the first question is telling as it implies an assumption of further evolution on the part of human beings “human thumbs are longer“. But are they really longer or is it that our other digits are smaller relative to other living primates? And the answer to that got increasingly complex as that depends also on body mass, how can this be estimated in the case of fossil creatures for which we only have skeletons?

As I finished my coffee, I thought again about how Crossrail has changed this area and how new spaces are developing. Perhaps it was apt, given the direction of the thought-flow that I had chosen an Ethiopian coffee to sample that day. Thought to be the origin of coffee, the coffee plant can still be found growing in the wild in parts of Ethiopia. Other coffees, other varietals, have developed (or been developed) since the coffee plant was taken from there to grow elsewhere, giving us an enormous range of flavours to try. The human thumb may not have evolved specifically to enable us to develop tool use, but it does enable us to pick up our cups of coffee.

Pour over science

floating, bouncing drops
How do you stabilise droplets of liquid water (or coffee) on a bath of water? And how long can you keep them on the surface?

On the 11th June, 2019 that is, in just under two weeks, we are going to try something exciting. Amoret Coffee in Notting Hill has offered to host the first ever “Bean Thinking’s evening of coffee & science”.

The idea behind what will (hopefully) become a series of evenings is to host a space for discussion and observation, exploring the physics within a coffee cup. On the 11th, we’ll be looking particularly at the phenomenon of “walking” droplets of coffee. These droplets can move across the surface of a cup of coffee and exist for many minutes (even days) if the conditions are right. And the conditions are fairly easy to create: we’ll be creating several such ‘walkers’ in the spacious upstairs area of Amoret’s Notting Hill branch that people can play with.

You can see such drops in your coffee in the morning. But what connects them to an early idea in quantum mechanics?

Although it takes the creation of certain conditions to achieve long-lasting droplets, you can often see them as you prepare a V60 pour over or even when dragging your (single-use) take-away cup over the surface of a table to create resonances on the surface of the cup. They crop up quite frequently, but why are they there at all and why do some last longer than others?

In addition to exploring these questions experimentally, we’ll also be discussing why these droplets sometimes ‘walk’ across the surface of the coffee and how this relates to an early interpretation of the phenomenon of wave-particle duality in quantum physics. How does something that you can sometimes see while brewing your coffee in the morning relate to the idea that fundamental particles such as the electron behave both as particle and wave? And what does this mean anyway?

It is hoped that future evenings will cover other topics such as climate change and coffee stains, I also hope that we will be lucky enough to have some of the coffee farmers that Amoret has direct-trade relationships with in order to explore these connections further. But, that is in the future, this time we are sticking with the fundamentals!

coffee at Watch House
There’s a lot of physics in a coffee. What do you see? Find out more at Amoret Coffee, 11th June 2019 or sign up to our events list.

So, if you are in London on the 11th June and would like to explore some physics in your coffee (or some coffee with your physics), please do come along to Amoret, from 5pm, for an evening of conversation and poring over science. We will be keeping people informed of plans for the evening (and for future evenings) via our events mailing list which you can sign up to here, or you can follow our progress on our Facebook events page here. Meanwhile, it would be helpful for planning reasons if you could let us know if you are coming either by signing up on Facebook or by emailing us. Looking forward to meeting some of you on the 11th.

Squaring the circle at Omotesando Koffee, Fitzrovia

Omotesando Koffee, Fitzrovia
The name “Omotesando” is represented solely by a square on a sign outside the shop. Is this a practical realisation of squaring the circle?

There was a lot of excitement late last year (2018) as the London branch of Omotesando Koffee opened just off Oxford Street. I watched as there were visits by Brian’s Coffee Spot, and Bex’s Double Skinny Macchiato and others, thinking that soon, I too would pop along. After all, it is a place that celebrates pour overs in central London. And yet, I went for the first time two weeks ago while meeting Sadiq of Amoret Coffee to discuss details of the first coffee and science evening being hosted in the Notting Hill branch of Amoret on the 11 June (more details and sign up page here).

On that first occasion, I had enjoyed a Rwandan by pourover and took in the minimalism and cubist geometry of the cafe but largely was too involved in discussing details of the event to think about the connections that the space prompted. And so a second visit was arranged. Again I found that the fold out chairs underneath the bench tables were a little too tall for me (though on the second occasion I didn’t fall off) but it did mean that, although I had a prime seat in front of the bar where they were preparing my pour over (a Burundi from guest roaster La Cabra), it was not easy to turn around to watch. It was however great to find that the cake menu at the order point at the front of the cafe clearly listed all the allergens in each of the cakes and so I was able to confidently enjoy a vegan banana cake with the coffee.

Omotesando Koffee, brownie with square revealed
Cubes and squares were a recurring theme inside the cafe

Omotesando offers a challenging space for a website built on the premise that any cafe offers an opportunity to explore connections to the wider world of physics if you just slow down, take in your surroundings and notice them. It is a space that seems to revel in minimalism. Most of the space is a fairly light coloured, mostly uniform wood. The bar is framed with a cube, a shape that seems to crop up all around Omotesando, even in some of the cakes. The fold out stools (circular) are made of the same colour of wood as the rest of the majority of the cafe (though there are a couple of exceptions to this which hint at the carpentry). Perhaps the idea is that we should focus on the coffee rather than the environment. And maybe that is where your mind enjoys wandering, but another thought suggested itself to my mind.

Sitting on the stool facing the window, wishing that I could turn around to watch the pour over being poured while remaining comfortable (there is a foot rest when facing forward), it struck me that sitting right in front of the bar did not help me when I wanted to use the glass of the window as a mirror to the inside of the cafe. The glass was perfectly transparent to my eye and reflected very little of the light behind me. The fact that the side of the (La Marzocco) espresso machine was transparent rather than metallic and revealed the pipework and wiring that enabled great espressos to be prepared (we also enjoyed an iced latte) briefly led me to consider why some materials are transparent and others not (and also how transparency varies as the frequency of light changes).

Banana bread and coffee with IoP bag
My pour over coffee, a banana bread and my IoP re-useable bag sitting on the table at Omotesando, Fitzrovia, London

But as I reflected further, I could see in my mind’s eye, the viewpoint of a deep sea diver looking up from the sea bed towards the sky. A circle of light, “Snell’s Window” opening above them. You can see images of Snell’s window where divers are framed by the effect in the photograph here. The effect is caused by the refraction of the light as it enters the water. Just as a straw (paper of course) appears bent as you view it through the glass of water, so light entering the sea will be bent by an amount given by Snell’s law. Even light entering at a grazing incidence will be refracted towards the ‘normal’ (the line perpendicular to the sea-air interface) and so if you work through the maths (there’s a good description here), you find that you will only see light from a cone of about 100 degrees around your view point.

Coffee reflections
What would you reflect on?

But although Otomesando has an entirely glass frontage, you do not feel you are in a gold fish bowl, nor can you only see a small window outside. The wide window instead offering plenty of opportunity for watching the office workers and builders scurry about outside. And, on writing this and looking through my photos of the cafe, I noticed that my photographs of the front of the cafe and of a coffee inside were both taken at shallow angles showing the reflections from the surface of the window and the coffee rather than the interior. An effect almost opposite to that of the deep sea diver. Omotesando Koffee offers a space where each cup offers further opportunities for reflection: more time for noticing the physics of the everyday. A great place therefore to spend some time thinking about, as well as enjoying, your coffee.

Omotesando is at 8 Newman Street, W1T 1PB

Is it summer yet? The Swallow Coffee shop, Shepherd’s Bush

Coffee Shepherd's Bush
Outside the Swallow Coffee Shop on Goldhawk Road

It was a spring day as we walked along Goldhawk Road towards the Swallow Coffee Shop. A sign, hanging above the door alerted us to the location of the cafe: an image of a swallow in flight, no name, just the image. A nod to the coffee houses of old perhaps that would advertise themselves with a picture above their doorway. The cafe is on the corner of Goldhawk Road and Richford Street and immediately strikes you as being more open and airy than some of the shopfronts we’d passed along the way. The counter is on the right as you go in and coffee is by Ozone.

The cakes looked good but sadly the tempting brownie was decorated with pistachio. Often I find that my nut allergy does have the incidental effect of keeping my waistline down. So sadly, once again it was just the long black that day. There is plenty of seating inside the Swallow cafe and we chose a table up the stairs, on a type of mezzanine level towards the back of the cafe. A map of London was on the wall next to us, which we studied a little in order to discover that a bit of artistic license had been taken with the geography. On the wall opposite, another map showed the region of Hammersmith. There is something interesting in the way that these maps were rendered. What was it that the cartographer intended to convey?

Lubrication station or plant stand
From mirrors to fireplaces and the nature of heat, what do you see in a coffee shop?

A sign above some plants indicated a “Lubrication Station”, perhaps needed by the Swallows on their hazardous migration to and from South Africa. Looking down towards the front of the shop it appeared that there was a mirror that I hadn’t previously noticed on the wall. It was a large, circular mirror. How come I had not seen it earlier as I walked in? And then it struck me, when I walked in, it was not a mirror but another framed map. It seemed as if it had changed its appearance because, from my location sitting towards the back of the cafe, the light was being reflected at a very shallow angle and so I was not able to see any of the ‘information’ behind the glass, only the reflections from the street. What appeared to my eyes as a mirror was in fact a map.

What do maps need to convey? A visual idea of the geography? Or perhaps, the way of getting from A to B. If it is the latter, there is no reason that the map should be geographically accurate and moreover, it could appear as a cartoon like strip of information so that you can ‘read’ your directions as you go along. We came across one such map a few years ago at St Michael’s Mount in Cornwall (see picture). Or, perhaps a more famous example of a geographically inaccurate but perfectly useful map is that of the London Underground. But then, the map may not be about getting from A to B at all but instead, should give an idea of the physical surroundings of a place or indeed could be intended to convey deeper  information such as the poverty maps of Charles Booth. Towards the end of the nineteenth century, Booth walked London mapping the levels of poverty (or affluence) in an area. You can access the maps here. In addition to seeing how some things have changed (or have not), the maps reveal how in London areas of relative wealth so often exist side by side with areas of relative poverty.
what information do we want a map to provide
A map at St Michael’s Mount in Cornwall offers an alternative depiction of the journey from A to B.

Booth apparently come up with the idea of the maps as he had disagreed with the suggestion that 25% of Londoners lived in poverty. And so he’d set out to conduct a statistical survey for himself. Categorising neighbourhoods into different groups according to relative income or wealth, he discovered that, in fact, 35% of Londoners were living in abject poverty, a worse result than he’d anticipated. His findings led to reforms such as the implementation of noncontributory state pensions and to the development of social surveys.

The work of Charles Booth somehow fits together with the research of John Snow who had similarly mapped the cases in the cholera outbreak of 1854 and so traced the source of the problem to the Broad Street pump. New fields of social research were being developed that relied on maps as a base for seeing the world. How we choose which information to include in the map (and by implication which to omit) and the way we choose to display that information, will affect how quickly our audience, or indeed ourselves, can understand the data presented. Some of our decisions are hidden but may affect how the data is later reported in the media. For example, did Booth define “abject poverty” for his maps in the same way as the previous efforts had shown “poverty” levels of around 25%?

In a world with ever growing amounts of data and eye-catching (click-bait) headlines, it is a problem that affects us still. What are the graphs and maps really telling us? Does the data really confirm our existing beliefs or is the devil in the detail of the display? If we find that our preconceived ideas are refuted (or perhaps worse confirmed), do we have the intellectual honesty to sit back, perhaps with a coffee, and question once more both our beliefs and the data that has challenged them? A cafe such as the Swallow, full of maps and prints, with plenty of seating and a light and friendly environment would be a great place to start.

The Swallow Coffee Shop is at 75 Goldhawk Road, W12 8EH

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