Author Archives: kayatesriseup-net

Focussing the sound at Spike and Earl

soya latte ginger beer

Soya latte and a ginger beer at Spike and Earl.

A few months ago, news came that the coffee roasting company Old Spike had opened a new café, Spike and Earl, down in Camberwell. Operating on similar principles to Old Spike, Spike and Earl aims to serve excellent coffee (and food and cocktails) with a social conscience. By employing those who have previously been homeless, Spike and Earl offers an employment (and training) route for people who may not easily otherwise have the opportunity. So although Camberwell is a bit of a trek, I was looking forward to trying this new place. As it was a late afternoon in November and the menu suggested that the dairy alternatives were only soya or oat, I decided to try a soya latte. (For any reader with a nut allergy, the current fashion of using almond milk means that you should always ask first if your cappuccino contains nuts). The baristas were friendly and confident in assuring me that they do not use almond milk (no danger of nut-cross contamination) but that their brownies did contain nuts (so I sadly had to pass on the brownie opportunity). My partner in these café reviews opted for a ginger beer.

There were a series of high tables with stools on the left hand side of the café. Presumably many people can therefore be accommodated when it gets crowded. However, at the time of our visit, it was fairly empty and we made our way to the rear of the café. Behind us, and behind closed glass doors, was a coffee roaster that we later discovered was part of the Old Spike roasting expansion. It’s always a nice touch to see coffee roasting happening as you drink but perhaps we needed to arrive earlier for that.

Bricks with holes Spike and Earl

Holes in bricks at Spike and Earl. Just a foot-hold or a suggestion for a great piece of engineering?

Drinks arrived together with complementary water and the soya latte was very smooth. Almost caramel like in the sweetness and very drinkable. It makes a pleasant change to have a latte once in a while. Light was playing tricks around the room as the sun was setting and the inside lights were becoming more prominent. But the striking thing about Spike and Earl was that the bricks used to support the tables and line the walls all had holes in them. On the wall running along the side of the café, (windows were on the other side), pot plants were placed in the holes giving the impression of the beginnings of a green wall. The holes in the bricks supporting the table meanwhile made an excellent footstool and were complemented by holes in the stools. A latte of course is largely made up of holes, or at least bubbles. The foam structure consisting mostly of air. How is it that some structures can be made better owing to what they don’t contain rather than what they do?

For example, if you imagine the difference between a latte and a cappuccino (but made out of metal rather than milk) that can be the difference between a successful tooth implant and a failure. We know from our coffees that bubble size can have a significant structural effect. But how about more fundamental properties, can the holes in bricks change things such as the way sound propagates?

Interior wall at Spike and Earl

More bricks with holes at Spike and Earl, this time with some plants escaping from them. The start of a green wall?

You may have heard about how different structures can be engineered to make materials “invisible” to certain frequencies of light. Imaginatively named “invisibility cloaks” are made by designing materials with patterns on them that change the path of an incident light beam. Because the effect on the light beam is due to the structure in the material rather than purely from the material itself, these materials have become known as ‘meta-materials’. When you remember that microwaves are a form of light, it is perhaps easy to see some of the applications of this research and one reason that it has attracted a lot of funding.

However there is an acoustic type of metamaterial that is far more similar to the bricks in Spike and Earl and that may find applications in medical imaging (ultrasound). Earlier in 2017, a team from the universities of Sussex and Bristol published a study about acoustic metamaterial ‘bricks’. Each brick had a differently shaped hole through the centre of it which delayed the incident sound wave by a specific phase interval (you can say it ‘slowed’ the wave). In order to work efficiently, the brick had to be of a height equal to the wavelength that the researchers were interested in and a width equal to half that wavelength. As they were investigating ultrasound, the bricks were therefore about 4.3mm square and 8.66 mm high.

By assembling the bricks together, the researchers found that they could steer a focussed beam of sound or even change the shape of the sound beam. This would have applications as diverse as targeting cancer cells with ultrasound to levitating a polystyrene bead. You can read more about their research here (or, if you have access to Nature Communications, their paper can be downloaded here).

soya latte Spike and Earl

Layering at the end of my soya latte. What would you think about?

Just for fun, assuming that the bricks supporting the table at Spike and Earl could be similarly turned into acoustic metamaterials, we could calculate the musical note that they would best work with. Estimating the brick at about 15cm square and remembering that is approximately  half the wavelength (λ/2) and using the speed of sound in air to be 330 m/s, we can calculate the frequency to be:

f = c/λ

f = 330/0.3 = 1100 Hz

Which is the musical note C#6 (with an explanation of nomenclature here).

As I finished my soya latte, strata of milk lined the cup. Reminiscent of the Earth’s layers or perhaps, metaphorically, our strata of understanding, there is certainly plenty more to ponder at this interesting new(ish) addition to the London café scene. So next time you are in Spike and Earl, do let me know what you end up thinking about, you never know where these thought trains may take you.

Spike and Earl is at 31 Peckham Road, SE1 8UB

 

Data overload at The Gentlemen Baristas

coffee Borough

The Gentlemen Baristas in Borough.

Borough is always such a great place to wander. Walking around the backstreets with their bits of hidden history. The other day, we had visited the market, wandered down Redcross Way past the old Crossbones graveyard and hit upon The Gentlemen Baristas on Union Street. It is difficult not to have heard about these Gentlemen and my visit there was long overdue and so, we wandered in to try this famous venue.

The shop front advertised itself as a “Coffee House”. A very accurate description and a nod to the Coffee Houses of the past. As it was shortly after lunchtime, it was very crowded with a diverse bunch of people and felt a little cramped at the counter. Nonetheless, the queue was quick and friendly baristas soon took our order allowing us to retire inside to try to find a table (no chance) or a stool next to a bar (successful). Around us, people were either chatting over their coffees or working on laptops.

While waiting for my long black (intriguingly described on their website as a “well mannered coffee”), I noted the various posters describing different types of screw head or parts of the human skeleton. Enough detail to be a phone distraction but surely there was more physics waiting to be seen in this convivial back room of a coffee house? A blackboard at the end of the bar, offered details of the wifi as well as a quote (slightly adapted) from PG Wodehouse about the benefits to friendship of a shared taste in coffee. On a shelf opposite the blackboard were a number of books including a thick book detailing coffee trading in years gone by. From the fact that the books were stacked horizontally, it would appear that they are not consulted often.

shelf books hats Borough

The lighting made photography difficult but you can see the books (and the hats) on this shelf at The Gentlemen Baristas

Sitting between this juxtaposition of wifi information and old books, caused me to pause. I have heard it said that we “know” more now than we have ever known in the past. That we have access to an enormous amount of knowledge merely through our phones. Is this correct?

On one level it is certainly un-arguable. Ninety percent of the world’s data in 2013 had been generated in the previous two years. If you need to find anything out, a quick duckduckgo (or if you have to, a google) will often lead to websites detailing all sorts of quirky bits of information. If we want to know the radius of the Earth or the size of an espresso grind, we no longer have to remember the answer, nor even really to have a feel for the answer, instead we can almost immediately find webpages that tell us (here and here).

And yet, this answer seems unsatisfactory. While there is an awful lot of information available to us at the tap of a phone, it is questionable whether that information translates to our own knowledge. Although collectively we can understand amazing things such as gravitational waves, individually we may struggle to explain how a toilet works. We need the plumber’s knowledge as much as we need that of the cosmologists. Does it matter who knows? What level of knowledge does someone need to have to say that they ‘know’ something?

coffee long black gentlemen baristas

Taking time to stop and think about what it’s all about. My coffee at The Gentlemen Baristas

Perhaps this appears a very strange cafe-physics review, where is the physics? But part of the rationale behind Bean Thinking is also to slow down and contemplate and it seems that The Gentlemen Baristas offers the perfect environment in which to do so. A café that mixes the new with the old, a space in which the practices of one can inform the other.

So to return the thought train to the area local to the Gentlemen: Writing in the second century AD, the Stoic philosopher Marcus Aurelius wrote

In death, Alexander of Macedon’s end differed no whit from his stable-boy’s. Either both were received into the same generative principle of the universe, or both alike were dispersed into atoms.

It is a quote you will probably find very easily via a search engine, or slightly less easily if you read his “Meditations”. But it is perhaps worth pondering, in what sense we ‘know’ what he was meaning. Strolling past the ribbons and messages memorialising the (estimated) 15,000 people who lay buried in the ‘outcast’ graveyard of Crossbones, what about our own attitudes to our modern outcasts? And perhaps more tellingly, our attitudes to those in positions of power or influence?

Perhaps it will take a lifetime of understanding our personal reactions to the poor, the prostitutes, the homeless and the powerful to really know what Aurelius meant. It certainly requires of us that we stop, pause and reflect on the knowledge that we come by. So it is far from obvious that it benefits us to use the wifi password rather than sit, slow down and contemplate. And where better to do so than in a friendly café with good coffee and seats to ponder the moment?

The Gentlemen Baristas can be found at 63 Union St, SE1 1SG

 

 

Back of the envelope calculations with coffee

coffee at Watch House

Coffee is generally a great help for reading, but to properly see the clouds in your coffee, it may help if you prepared yourself a brew now.

To read this post it will help if you have a cup of lovely, hot, freshly prepared coffee or tea with you.

Got it? Ok, let’s begin.

A few weeks ago, there was a talk given by Prof. Paul Williams of the University of Reading about the Mathematics of turbulence and climate change. An entertaining talk about the importance of, and the effort of comprehension required to, use mathematics in order to understand climate change. There were several thought provoking comments through the talk that demanded further reflection. But one, almost throw-away comment has been bugging me since. Although I’ve forgotten the exact words, they went along the lines of

Of course mostly we think about the impact of climate change on the weather, after all, we live in the bottom few metres of the atmosphere and so that is what mostly affects us. What I would like to talk about is the effect of climate change on airplane turbulence…

The bottom few metres of the atmosphere? It’s true. The bit we’re most experienced with is just a tiny portion of it. It’s about perspective. To us, it seems the atmosphere is very big, we pump all sorts of exhaust fumes into it and they disappear. We have expressions such as “the sky is the limit” that suggests that the atmosphere is a huge volume of gas. We all know it is not really limitless, but day to day, on our human scale, it seems enormous.

Now the mathematics that Prof Williams uses to calculate the effect of changing temperature and carbon dioxide levels on the jet stream (and consequently the turbulence felt by planes) is way beyond the sort of back of the envelope calculation that we can do with a cup of tea (or coffee). Understandably, to even start to comprehend these mathematical models requires years of training in maths and physics. However, assuming that we are not ourselves atmospheric physicists, there are things that we can do to help us to see our atmosphere in a more realistic way. And this is where your coffee comes in.

Earth from space, South America, coffee

Clouds swirling above our common home. But if the atmosphere is represented by the white mists on the surface of a cup of coffee, what size coffee are we drinking?
The Blue Marble, Credit, NASA: Image created by Reto Stockli with the help of Alan Nelson, under the leadership of Fritz Hasler

Take a close look at that coffee. Assuming it is not cold brew, hopefully your coffee or tea is still fairly warm. Watch the surface of the coffee. You may start to see movement such as convection in the mug, perhaps you can see a film of oil on the surface. But do you see something else? In very hot tea or coffee, you should be able to see what appear as white mists hovering over the surface of the cup*. It is easy to miss them, but as you watch, cracks suddenly appear in the mists and then there is a re-organisation of them which allows you to start to see them dancing over the surface of your drink*.

These mists are the result of the levitation of many thousands of droplets of water just above the surface of the coffee. I have written about them elsewhere. No one knows quite how they levitate above the surface, but what is known is that they are at a distance of up to 100 μm (0.1mm) from the surface of the coffee.

Let’s construct a scale model of our coffee as the Earth and its atmosphere. These mists can then do a fairly good job of representing the atmosphere with its drifting clouds. So, assuming that the mists are the atmosphere and the coffee is the Earth (on the same scale), what size of coffee would you have to have? Would you be drinking:

a) an espresso

b) a long black

c) a venti

d) a ristretto

Think you know the answer? Let’s work it out with a “back of the envelope” calculation. The easy bit is deciding the radius of the Earth, it’s just under 6400 km, our first problem comes with the estimate of the thickness of the atmosphere. There are several layers in the atmosphere. The one that we are most familiar with, the one closest to us is the troposphere. This extends for the first 16 km above the surface of the Earth (though this varies with latitude, it is only 8 km at the poles). Most of our weather happens in this region and it is also the layer of the atmosphere that planes fly in. Above the troposphere is the stratosphere which extends until about 50 km. Beyond that, things get very rarified indeed though the boundary between our atmosphere and “space” does not happen for several hundred km (indeed, the orbit of the International Space Station is in this bit of our extended atmosphere).

Coffee Corona

Look carefully around the central (reflected) white light. Can you see a rainbow like spreading of the colours? Another manifestation of the white mists on the coffee surface.

As we are mostly concerned with the weather (and airplane flight etc) though, it seems sensible to define the atmosphere height to be the top of the troposphere. After all, most of us will tend to think that the Space Station is in, well, space. This definition is further justified by the fact that about 75% of the mass of the atmosphere is found within this region (the atmosphere gets thinner as you go higher).

What size coffee would we be drinking if the white mists (0.1 mm above the coffee surface) represent the 16 km of the Earth’s atmosphere? We’ll call the coffee height, hc. Our first step is quite easy, we can just use the ratios of the heights to calculate the coffee size:

(height of troposphere)/(radius of Earth) = (white mist height)/(height of coffee)

A bit of rearrangement:

height of coffee = (white mist height)*(radius of Earth)/(height of troposphere)

hc = (0.1) * (6400)/16

hc = 40 mm (4cm)

So for the mists to represent the atmosphere in your coffee, you would need to be drinking a 4cm tall coffee which is probably a smallish long black. I would leave it to you to calculate the coffee size for the atmosphere defined as outer space (beyond the orbit of the International Space Station). But perhaps this perspective gives us another way of looking at our atmosphere. Vast indeed, but fragile too.

*As I was writing this, I had a warm, very drinkable, cup of coffee but it wasn’t steaming and so showed no white mists over the surface. The mists are best seen in freshly made, very hot drinks.

An odd one out at Shot Espresso, Parsons Green

tubes playing with perspective Shot Espresso Parsons Green

The view from the ‘conservatory’ in Shot Espresso, Parsons Green

A couple of weeks ago we were wandering around the Parsons Green area in search of a coffee. Near the station, was a small shop front with a familiar name. Not quite a chain, but the logo of Shot Espresso is well known to me from its relatively new outlet in Victoria. It turns out that the Parsons Green branch is one of four outlets for Shot Espresso which started just around the corner in Fulham.

The staff were very friendly and took our order before we found seats at the back of the café. Although there was plenty of seating near the counter it was all taken, clearly this is a popular haunt on a Saturday afternoon. This did mean however that we found a cosy table in a small but very bright area, almost like a mini-conservatory. It seems we often have a long black and a soy hot chocolate and today was no exception. The hot chocolate was apparently perfectly well done my long black was fruity and drinkable, offering a perfect flavour backdrop against which to appreciate the area of the café.

Then a tricky decision. Ordinarily, I am not a fan of reviewing chains (though there is a question, does four branches equal a chain or not?). I’m a great fan of what an independent coffee shop can bring to an area, a place where the owners can be found behind the counter and you can really get to know a friendly space. However Shot Espresso is not that large a chain and the branch at Parsons Green had the feel of a local. The staff when we were there certainly took an interest in the running of the shop and, another factor in my decision to review, there were so many things to notice here.

infinity, shot espresso

Infinite tables? The logo on the table next to us at Shot Espresso Parsons Green.

I’ve already mentioned the light in the conservatory, there were also the light fittings in the main part of the bar. Wooden outlines of cubes around a light bulb that played with your image of perspective. On the tables next to us, the symbol of the manufacturers was similar to the symbol of infinity, why? But then, an oddity that prompted a mathematical curiosity. On each table was a miniature watering can holding sugar. It’s almost a game:

You have a mug of coffee, a cup of hot chocolate, a doughnut and this watering can on your table. Which is the odd one out and why?

If you answered the watering can, you would have been correct. Topologically the mug of coffee, cup of hot chocolate and the doughnut are the same whereas the watering can is quite different. What does that even mean? It means that in terms of shape, a doughnut can be morphed into a coffee mug which can clearly be morphed into a tea cup as they each have one hole through them. The watering can however has multiple holes, not just to hold it and to let the water out but also, in this ornament design, at the join of the body to the spout (look carefully). This means that there is no way that you can transform a watering can into a doughnut, they are different categories of shape.

table at Parsons Green Shot Espresso

A coffee cup and a miniature watering can. But which has more in common with a doughnut?

This field of mathematical study (which is known as topology) has, in recent years, taken on enormous significance to physics in terms of understanding some odd effects including the way that some materials conduct electricity (or not). Indeed, it has become so important that it was the subject of the 2016 Nobel Prize (you can read the citation here). And yet, even for someone who works in solid state physics and should have a mathematical background, trying to get my head around this subject is extremely difficult.

Which got me thinking about something similar. When teaching, it is sometimes apparent how much mathematics appears as if it is another language. And in parallel with language, it requires a fluency to appreciate its beauty. And further, even with a fluency, to appreciate some use of the language requires more than just fluency but immersion, a concentration, an attention to the words. Perhaps an analogy is needed. Although fluent in English, I do not usually immerse myself in reading it. Consequently, I find the poetry of John Betjeman amusing and ‘readable’, but the poetry of Gerard Manley Hopkins very difficult. With patience, and advice from others, occasionally I can gain a flash of insight into a poem of Hopkins and realise the brilliance of the language but more often I struggle. What I would never imagine doing is saying “I can’t read English, I was never good at it in school”.

And it is here that it seems to me the parallel with mathematics ends. For while we can have fun with algebra, understand some of the beauty in calculus and perhaps struggle with topology, we nonetheless seem happy in our society to say “I can’t do maths, I was useless at it in school”. We accept boasts about mathematical illiteracy when we would blush to say similar things about our native language (whether it is English or another language).

Why is that?

watering can, Shot Espresso, Parsons Green

A closer look at the watering can. The number of holes in the join to the spout would make this useless as a plant watering device.

Surely there are few who are genuinely mathematically illiterate, at least, not to the extent that it is ‘boasted’ about within society. Indeed, you find many who are happy to admit that they don’t “do” maths, actually just mean that they would prefer to use their phone to calculate something. Just as with a spoken language, the language of mathematics requires practise. For it is practise that allows us to appreciate the fun of mathematics just as it is practise that allows us to read poetry. Why do we deny ourselves the fun of a language because it is fashionable to admit illiteracy in it?

If you would like to push yourself with some mathematical poetry, you can read about topology, coffee and doughnuts here or in more detail here and more information on the 2016 Nobel Prize can be found here. In the meantime, if you see something mathematically beautiful in a café, please do share it, either here in the comments, on twitter or on Facebook.

Enjoy your coffee, tea or doughnuts.

Shot espresso can be found at 28 Parsons Green Lane, SW6 4HS

 

 

 

 

Chemical extraction in a V60

chromatography, paper chromatography, V60

Brewing a coffee, insight into analytical chemistry

Ever considered the connection between your morning brew and a century old technique that, it is fair to say, revolutionised analytical chemistry?

Last week, a new coffee arrived in the post from the Roasting House coffee club, followed shortly by an email with details about that week’s coffee. This is not unusual, the coffee club means that a different coffee arrives every two weeks. What was slightly unusual was the email which started:

“There are some brief tasting notes on the bag of coffee we sent you, but before you go on and read the more detailed description, have a good taste of the coffee yourself….”

The opportunity to do so finally arrived and I prepared a V60. First measuring out the freshly ground beans, rinsing the filter, watching the bloom, then slowly pouring the remaining freshly boiled water onto the grounds, all the while noting the aroma.

Taking this opportunity to slowly prepare (and appreciate) a coffee, I noticed that some of the soluble elements in the coffee climbed the filter paper during the pour. A few hours afterwards, the paper had gained a circular rim of coffee solubles around the top of the paper. Although in many ways quite different, this effect was very reminiscent of the technique of chromatography.

Roast House coffee, tasting chromatography

The coffee in question. What tasting notes would you get if you slowed down and tried this one?

The biggest difference between the behaviour of the V60 filter and “paper chromatography” is that in the former, the bottom of the filter paper is continuously immersed in both the sample (coffee) and the solvent (water). In chromatography on the other hand, a drop of the sample (e.g. coffee or ink) is put onto the filter paper which is then placed in a solvent (e.g. water, ethanol). Different components within the sample travel different amounts up the filter paper depending on how soluble they are in the solvent and how they interact chemically with the filter paper. So different components will travel different distances up the filter paper before they get stuck while the solvent continues to travel up the paper. All else being constant, each component always travels a certain distance relative to the solvent and so this provides a way of separating chemical components ready for further analysis or identification.

Perhaps you remember using chromatography to separate the colours in an ink pen at school? The ink was spotted onto a piece of filter paper and then immersed in water. We watched as it separated into various colours illustrating the number of different dyes that had been used to make up the ink. When used professionally though, the chromatography technique can be used to investigate trace impurities in soil, air, drinking water etc. It has even been used to analyse the components in coffee. From something that can be done in school science, it is an incredibly powerful chemical technique.

What was surprising was that the technique of chromatography was not invented until 1903, while the idea of using paper in chromatography only came about in 1944¹. Those who first used chromatography as a method to identify chemicals (in plants), did so using columns of powder rather than paper. Paper chromatography was invented to investigate the separation of amino acids and specifically was used to understand the composition of the antibiotic tyrocidin¹. Just as the ink in our school experiments separated into different dyes, so the chemicals that they were investigating would separate into different components, different chemicals would stay at different heights on the filter paper.

Since its invention, the technique had been extended to include gas chromatography rather than just liquid and has been developed to be extraordinarily sensitive. It is now possible to analyse chemicals with a mass of just 10^-15 grammes, a quantity which is too small to even easily imagine. Even just a couple of decades after the invention of the technique it could be said:

“Amino acids… could now be separated in microgram amounts and visualised…. (Paper chromatography) would allow one within the space of a week [to do some analysis]… which until then could very well have occupied the three years of a Ph.D….”¹

V60 chromatography chemistry kitchen

A few hours later and the coffee had travelled up the filter paper with the solvent (water).

However, to return to the coffee. Through tasting rather than chemistry, I obtained a toffee aroma, with earthy notes and hints of redcurrant that evolved as the coffee cooled into a sweet toffee taste. The tasting notes further down the email on the other hand said:

“There’s a rich chocolate base, a kind of woody pine taste, sweet summer fruits, even tobacco. Remember, taste it before you judge it! Tobacco notes and woody pine don’t sound particularly appealing and maybe you don’t taste them at all!”

Much more descriptive than my effort. It seems I need to return to my V60 and improve my tasting ‘chromatography’. There are so many ways to slow down and appreciate a good coffee, what do you notice in yours?

A ‘coffee tasting wheel’ can be found here if you, like me, would like to improve your coffee tasting ‘chromatography’.

¹Chapters in the evolution of Chromatography, Ed. John V Hinshaw, Imperial College Press, 2008

Light and gravity at Tab x Tab, Westbourne Grove

drinks in ceramic mugs, Westbourne Grove

A soya hot chocolate and my black coffee at Tab x Tab

Earlier this summer, a new café opening on Westbourne Grove attracted a lot of attention. “Tab x Tab” quickly received reviews from Brian’s Coffee Spot (who noted the unusual espresso machine), Bean There at and Doubleskinnymacchiato. Bean There at also suggested that there should be plenty to ponder at Tab x Tab when I finally got the chance to get there. And so, a trip to this café had been on the agenda for a fair while.

Wandering into the café, it seemed exactly as described by the reviews: clean, sharp interiors in a modern building. It was fairly crowded when we arrived just after lunch and so we ordered before taking a seat at the bar (two of the few seats left). I had a long black while my fellow imbiber had a soya hot chocolate. The drinks arrived in those distinctive mugs mentioned by doubleskinnymacchiato (and pictured above). As we had just had lunch, on this occasion we didn’t check the edibles on offer but with plenty of other reviews of the coffee and the cake, I’m sure that you’ll find recommendations there (I understand the avocado on toast with cashew nut is well worth trying).

Graphite, double layer graphene, stacked hexagons

Plant on two slates at Tab x Tab, Westbourne Grove

Sitting down to enjoy our drinks, the first thing to notice was that Bean There at was absolutely right. Despite the slightly minimal and elegant decoration, there were plenty of things dotted around that were slightly quirky. Firstly there was the plant that had been placed on two hexagons of slate that had been ever so slightly displaced from each other, presumably for aesthetic effect. Could this link to graphene and graphite with their strong intra-layer bonding and weak interlayer bonding (so the hexagons of carbon in graphite slide over each other)?

Then there was the selection of items for sale that also provided food for thought. Books and other items from the School of Life, something to think about as you stop with your coffee perhaps. In the other direction, on the counter top, a couple of Venus Fly Traps were waiting for their lunch. There is so much we have yet to learn about the symbiotic relationships between plants and animals and especially between plants and fungi. As we looked further around the café, there was something else a little odd. Just as the name “Tab” was written both the correct way and upside down in the window, so the plants in the hanging baskets were hanging upside down.

which will win, gravity or light

Plants hanging upside down in the window at Tab x Tab

This seemed a bit strange in itself. Plants have a tendency to move upwards towards the light. This behaviour of plants (and trees in particular) provides one way to identify which way is south when walking in the country without a compass¹. It is odd to see a plant growing downwards and suggests that the plants in the window are regularly rotated so that they don’t try to reach up. As Simone Weil wrote “Two forces rule the universe: light and gravity”². Which would win in the end? To be fair, Weil was not referring to the light that streamed through the windows in Tab x Tab giving the plants the force they need to move upwards. Nonetheless, whether one is thinking literally or analogously, it is an interesting question what pulls us down, what brings us up?

There is a story that Newton arrived upon his idea of universal gravitation by contemplating a falling apple. Considering that the plants were approximately 2m above the floor level, and using the fact that the acceleration due to gravity, g,  is 10 m/s², if the plants were to fall from their hanging position, they would take:

s = ½gt²

t = 0.6 seconds

to fall and smash to the ground*. While this brings to mind Newton’s experiments dropping pigs bladders filled with liquid mercury from the dome of St Paul’s Cathedral, it is worth instead thinking more about the universal nature of the gravitational force. This is of course what made Newton’s idea of gravity different from the theories that had preceded it. People had known that if an apple fell from a tree (or a plant fell from its hanging basket) it would fall to Earth. What was key to Newton’s idea was that what applied to the apple, applied to all other masses too. The same maths that could be used to calculate how fast a plant dropped, could be applied to the Moon. So, if this was the case, could we calculate the orbital distance of the Moon in the time it took us to enjoy a coffee at Tab x Tab? We know that the Moon’s orbital period is τ = 27.3 days (2.36 x 10^6 seconds) so assuming that the gravitational force acting on the Moon is balanced by the centripetal force, we can equate the two:

Gravity: F = GMm/r²

Centripetal: F = mv²/r

Where, G is the gravitational constant (6.67 x 10^11 Nm²/kg²), M is the mass of the Earth (5.97 x 10^24 Kg), m is the mass of the Moon and r the moon’s orbital distance (which is what we want to calculate). If we assume that the Moon travels in a circular orbit (not quite true but not a bad first approximation), then we know the speed, v, of the moon in terms of the orbit period, it is just:

v = 2πr/τ

A bit of re-arrangement and some plugging in of values leads to a back-of-the-envelope value for the Moon’s orbital distance of 383 000 Km. A value that does not compare badly at all with the average distance of the Moon given by NASA as 384 400 Km.

Perhaps if we’d stayed for an additional flat white we could have refined the calculation somewhat and so obtained a value closer to reality. Nevertheless, the fact that the force that is pulling the plant down at Tab x Tab is the same as is pulling the Moon around the Earth, and that we can quickly check this (and get an approximately correct answer to our calculation), is one of those ‘wow’ moments in physics. Realising the universality, and elegance, of certain mathematical relations. So perhaps it is entirely appropriate that this thought train of mathematical elegance was prompted by the quirky but aesthetic elegance you will find at Tab x Tab.

Tab Tab can be found at 14-16 Westbourne Grove, W2 5RH

¹ The Walker’s Guide to Outdoor Clues & Signs, Tristan Gooley, Hodder & Stoughton, 2014

² Gravity and Grace, Simone Weil, Routledge (1995 vsn)

*Although you could use a more accurate value for g, the error on the estimate of the height of the plants makes such precision potentially misleading. The value 0.6 seconds is absolutely a back-of-the-envelope, calculation.

Coffee under the microscope

Inside Coffee Affair

There are many great cafés in London serving excellent coffee but inevitably a few stand out. One such café is Coffee Affair in Queenstown Road railway station which ‘inhabits’ a space that really encourages you to slow down and enjoy your coffee while just noticing the environment. An ex-ticket office that whispers its history through subtle signs on the parquet floor and in the fixings. The sort of place where you have to stop, look around and listen in order to fully appreciate it. And with a variety of great coffees on hand to sample, this is a café that is a pleasure to return to whenever I get the opportunity.

So it was that a few weeks ago, I happened to wander into Queenstown Road station and into Coffee Affair. That day, two coffees were on offer for V60s. One, an Ethiopian with hints of mango, peach and honey, the other, a Kenyan with tasting notes of blackcurrant and cassis. But there was an issue with them when they were prepared for V60s. The Ethiopian, “Gelana Abaya”, caused a considerable bloom but then tended to clog the filter cone if due care was not taken during the pour. The other, the Kenyan “Kamwangi AA”, did not degas so much in the initial bloom but instead was easier to prepare in the V60; there was not such a tendency to clog.

What could be going on?

So we had a look under the microscope at these two coffees. Each coffee was ground as if it was to be prepared in a V60 and then examined under the microscope. Was there any difference between the appearance of the Gelana compared to the Kamwangi? A first look didn’t reveal much. Magnifying both coffees at 5x, it could be said that the Kamwangi had more ‘irregular protrusions’ on the ground coffee compared to the smoother Gelana, but it was hard to see much more:

coffee under the microscope

The samples of ground coffee imaged under an optical microscope at 5x magnification. Kamwangi is on the left, Gelana on the right. “500 um” means 500 micrometers which is 0.5 mm.

So, the microscope was swapped to image the coffee in fluorescence mode. It was then that the cell structure of the coffee became clear. Here are the two coffees magnified 10x:

Fluorescence microscopy 10x, Ethiopian, Kenyan, Kamwangi, Gelana

Fluorescence microscope image of the two coffees at 10x magnification. Note the open structure in the Kamwangi and the more closed structure in the Gelana.

and at 20x

Kamwangi and Gelana coffee under the microscope

A fluorescence microscope image magnified 20x – not ‘um’ means micrometers (1/1000 of a mm), so the scale bar represents 1/10 mm.

So there is perhaps a clue in the cell structure. It seems as if the Kamwangi structure is more open, that somehow the cells in the Kamwangi break open as they are ground but the Gelana somehow keeps its cells more intact. Could this be why the Gelana blooms so much more?

Which naturally leads to a second experiment. What happens when you look at these two coffees in water under the microscope? Here the fluorescence images didn’t help as all you could see were the bubbles of gas in each coffee but the optical microscope images were of more interest.

optical microscope image in water

The two coffees compared under the microscope while in (cold) water. Magnfied 5x

‘Bits’ broke off the Kamwangi as soon as water was added but in comparison, there were far fewer bits of coffee breaking off the Gelana grains.

So what do you think has happened? If you remember our question was: when these two coffees were prepared with a V60, the Gelana bloomed a lot but then clogged in the filter (without extreme care while pouring the filter). Meanwhile the Kamwangi did not bloom so much but also did not clog the filter, what could be happening?

From the microscope images, it appears that

  1. Before adding any water, the cell structure in the Kamwangi is more open, the Gelana appears ‘closed’.
  2. When water is added, there are many more ‘bits’ that come off the Kamwangi whereas the Gelana does not show so much disintegration on the addition of water.

If pushed for a hypothesis, I wonder whether these two observations are linked. What is happening is that the cell structure in the Kamwangi is, for whatever reason, fairly fragile. So as soon as it is ground, the cells break up and a lot of the carbon dioxide is released. Consequently when water is added to it, the bits of broken cell quickly disperse through the water and it doesn’t seem to ‘bubble’ that much. In comparison, the Gelana cell structure is tougher and the cells only open up when water is added. I wonder if this means that the ground Gelana coffee will swell rather than break up and so ‘jam together’ as each grain tries to expand rather like trying to inflate many balloons in a bucket. They will push against each other and prevent water from easily percolating through the ground coffee.

Sadly, many more experiments would be required before we could see if there’s any truth in this hypothesis however that does provide a great excuse, were one needed, for many return trips to Coffee Affair. Meanwhile, what do you think? Do any of the images stand out to you and why? What do you think could be the cause of our V60 coffee mystery? I’d love to hear your thoughts so please let me know either here in the comments section (moderated and experiencing a lot of spam at the moment so please be patient), on Facebook or on Twitter.

Phlogiston in the Watch House

Watch House coffee Bermondsey

The Watch House in Bermondsey

At the end of Bermondsey St, tucked away in an odd looking building on the corner, is a café known as the Watch House. Stepping inside you are met with a very strange impression: this is far from your normal rectangular room. Instead an octagonal space, complete with Victorian style tiling and wood burning stove greets you. There are about five small tables inside, which were all occupied (some shared) when we arrived late in the lunch hour. So we sat at a table outside, although there was also bench seating on the other side of the door and a lovely park just next door, the old St Mary Magdalen graveyard.

The building itself dates from the time when the “watch house” was the base for a makeshift local constabulary that would monitor the local area ensuring that no body-snatchers were operating in the graveyard next door. The body snatchers used to ‘acquire’ recently buried bodies for use in anatomy classes at the capital’s teaching hospitals. Nowadays, as with many other disused burial grounds in London, the graveyard next door has been transformed into a park. On the other side of the café, a drinking fountain (the gift of a Henry Sterry Esq.) is embedded into the wall. An interesting feature reminding us of the drive to provide drinking water to London’s population both then and now with the newly installed fountains at the nearby Borough Market.

coffee at Watch House

What fantastic colour in this filter.

As I placed my V60 on the table outside, the light shone through it making the coffee appear to glow with a deep red tinge. Temporarily ignoring my normal idea that such transient beauty can’t be captured, I tried to photograph it, an endeavour that predictably failed to capture the full radiance of the cup. Nonetheless, the clear red coffee did not have significant sediment at the bottom of the cup. Perhaps this is not surprising, it was a V60. But nevertheless this lack of sediment has a connection with the water fountains both at the Watch House and at Borough Market and the wood burning stove. You could even make a macabre link to the graveyard next door. But without pursuing that last one too much, the link is Antoine Lavoisier (1743-1794) and the transmutation, or not, of water into earth.

The problem was this: In the early seventeenth century Jon Baptist Van Helmont had planted a 5lb (2.3 kg) willow tree into a pot of soil of mass 200 lb (91 kg)¹. He covered the pot of soil and only allowed rainwater into the tree/pot system for 5 years. At the end of his experiment, the mass of soil was unchanged but the willow tree was now 169 lb 3 oz (76.8 kg). Clearly, the “element” water had transmuted into the “element” earth* and so added to the mass of the tree. A few years later and scientists boiling distilled water (which had of course been purified by previous boiling) noticed that there was always a solid residue left after the water had boiled away². Another piece of evidence for the transmutation of water into earth.

Lavoisier, who became known as the father of modern chemistry, thought differently. He had been interested in obtaining clean, safe drinking water for the inhabitants of Paris and had noticed that when rainwater was repeatedly distilled, the amount of solid residue left after boiling decreased with each distillation. How was this reconcilable with the idea that each time you boiled water part of it became the element earth? But if water wasn’t ‘transmuting’ into earth, what could explain the solid residues observed by the other scientists of his day?

Lavoisier suspected the potash or soda used in making the glass vessels used in the experiments. He thought that this could be dissolving out of the vessels when the water was boiled, leaving what looked like a solid residue at the bottom of the cup². To demonstrate that this could be the case, Lavoisier took a sealed container of water called a ‘Pelican’ (which has two arms to allow the water vapour to cool and drip back down to the base of the unit). He first weighed the water and the vessel, separately and together and then boiled the water in the sealed pelican for 100 days. After 100 days he weighed the container-water system again. The total mass had not changed. However, when they were weighed separately, something odd had happened. The glass vessel (the pelican) had lost some mass while solid salts had appeared in the vessel. Although these salts weighed slightly more than the mass lost by the pelican container, Lavoisier considered the discrepancy within error thereby showing that the ‘transmutation’ observed by other scientists was actually salt dissolving out of the glass vessel.

Lavoisier’s experiments were an important contribution to the development of experimental method as well as a refutation of the old idea of the transmutation of the elements earth-air-fire-water.

Lavoisier, drinking fountain, Bermondsey

The fountain on the side of the Watch House. How had a need for supplying the public with drinking water shaped our scientific thinking?

Which leaves one last connection: the wood stove. Since the dawn of humanity, there has been the question “what is fire?”. By the time of Lavoisier, fire was explained by the idea that matter contained more or less “phlogiston”. Something could catch fire if it contained a large amount of phlogiston, it would not ignite were it to have too little phlogiston³. One observation clearly explained by the phlogiston theory was the observation that a burning candle, covered by a glass bell jar, would extinguish itself. The idea was that the candle (which contained phlogiston) released that phlogiston into the air. If the candle burned within a jar, the air surrounding the candle would became saturated with phlogiston. Once saturated, the air could ‘hold’ no more phlogiston so none could escape the candle wick. This would mean that the flame would go out.

Lavoisier, now recognised as one of the three independent co-discoverers of oxygen, showed that oxygen, not phlogiston, was needed for burning to occur. The question is how did he do it? And a question for you, when you are enjoying your sediment free delicious coffee next to a warming wood fire: how would you?

 

*to be fair to Van Helmont, it is hard to blame him for arriving at this conclusion. It was still a few centuries before photosynthesis was discovered and the idea of the four elements of fire, earth, water and air was still active in his time.

The Watch House is at 199 Bermondsey St, SE1 3UW

¹”Lavoisier in the year one”, Madison Smartt Bell, Atlas Books (2005)

²”Lavoisier”, Jean-Pierre Poirier, University of Pennsylvania Press, (1996)

³”From phlogiston to oxygen”, John Cartwright, Hatfield (2000)

 

Coffee cup recycling

a take away cup

It is recyclable, but not easily so.

That old subject again, the recyclability of take-away coffee cups. But before you groan about our disposable culture, there has recently been some great news, at least as far as the university sector is concerned. Regular readers may know of the Bean Thinking list of Top UK Universities for Coffee Cup Recycling. You may also be aware of just how short that list has been. Now though, there are signs of change. Perhaps because it is the start of the academic year, several universities including Oxford Brookes and the University of Bedfordshire have announced new schemes for recycling their cups with Simply Cups.

Owing to the way the cups are made it is extremely difficult to recycle them; although they are technically recyclable, very few companies have the capabilities. Consequently, the majority of the cups that we use for our take-away are just thrown-away, taking many decades to break down.

compostable, coffee cup, disposable culture

Using compostables can be a step in the right direction.

It is often our universities that do the research showing just how environmentally damaging our disposable culture can be. Nonetheless many university catering departments continue to serve coffee in “disposable” cups without putting in place any scheme to recycle them. Over a year ago I started a list of the UK’s top universities for coffee cup recycling. It would be thought that it should be extremely easy to be listed here. To be listed, all a university has to do is take a responsible attitude to it’s take away coffee cup use. Preferably, they would discourage take-away coffee cup use altogether. As Loughborough University recognises, slowing down, talking with colleagues over a stay-in (washable cup) coffee can be far more productive than scurrying away with your non-degradable cup.

However, often we feel that we don’t have time to sit down for a coffee and need to take-away. At this point, to be listed on the guide, all that a university would have to do is either invest in compostable cups (despite the caveats*, this is at least a step in the right direction) or institute a scheme to collect and recycle their coffee cups (as has been done at the University of Bath, Bedfordshire, Kent, Loughborough, Manchester Metropoliton and  Oxford Brookes University).

As may be apparent from the fact that the universities can be listed within this short article, the current list is woefully short. Even after the recent good news from Oxford Brookes and the University of Bedfordshire. Most universities, including my own are sadly still not on it. So, what can you do if your university is not listed here?

  1. If you think it should be listed but hasn’t been it is very highly likely that I just don’t know about it yet, please let me know by contacting me through email, Twitter or Facebook.
  2. If your university is doing very little to discourage disposable cup use: Write to the catering department and waste management department of your university to let them know your concerns. When writing, be aware of the fact that they have probably considered this problem before and are aware of the issues but have concerns/limitations that have prevented them from implementing a policy. Consumer pressure can help to change their minds but there may be (what appear to them to be) valid reasons that they have not yet done so.
  3. Use a re-usable cup. Even if your university does not charge extra for using a disposable cup/give a discount for using a re-usable (thereby encouraging the use of re-usables), systemic change starts with individuals. Be the start of the change you want to see. You can find a review of various re-usable coffee cups here.
  4. Refuse to buy your stay-in coffee if you are served it in a take-away cup. Good coffee deserves to be enjoyed in appropriate cups and poor coffee should be avoided anyway.

You can find the list of the UK’s top universities for responsible take-away coffee cup use here.

 

*The word ‘compostable’ does not necessarily mean that it will compost in a home-composting environment. For this situation to be preferable to the ordinary disposable cup, it would be necessary to have some form of industrial composting facility in place.

Constructive interference at Frequency, Kings Cross

exterior of Frequency Kings Cross

Note the tiles. Frequency, Kings Cross on a rainy day.

It was a rainy afternoon when we ventured to Kings Cross and into Frequency. Suggested by the London’s Best Coffee App as the closest café to our then location, we made our way through puddles and rain onto Kings Cross Road. At that point, a brain-freeze meant that we couldn’t see where Frequency should be. The map on the app was implying that we were extremely close but there didn’t seem to be a café around. Then we saw it in front of us! The striking black and white tiling on the floor somehow hiding this shop-front from view.

The tables inside matched the tiling outside. Black and white triangles meeting at a point. My long black (from Workshop) was placed close to the intersection of these triangles. The coffee arrived in a mug, more cylindrical than standard coffee cups and so closer to mathematical models of coffee cups that are used in explanations of convection and rotation in the cups. An interesting change of aesthetic that also changes the internal dynamics of the coffee. A nice touch was that the mugs were also coordinated with the tiling, though to be fair I hadn’t noticed that at the time.

The coffee itself was extremely fruity, a lovely warming brew to enjoy while watching the rain outside. The interior of the café meanwhile was decorated with a lot of wood around together with a couple of music stands. Perhaps the music stands make sense in a café named Frequency. Indeed, according to the review on London’s Best Coffee (or as it is now known, Best Coffee), there are plans to build a music recording studio here as well as having live musical performances. However, also mentioned in that review was the fact that this café had been designed and built from scratch with the help only of online tutorials. Which makes a particularly resonant connection with something I noticed here.

mug of coffee at Frequency

Coffee at Frequency.

What caught my eye as I contemplated this café was the one bit of bright colour on the ceiling. It was also something that hints at problems that can crop up when you design and build your own electrical circuits: Parallel wires (in this case leading to the lightbulbs). Perhaps in the café, these were intended to represent music staves, certainly that would fit in the theme. However to an experimental physicist who dabbles in designing pieces of kit for electrical measurements, these parallel lines leading to a light mean something entirely different.

They mean noise.

When you are designing a piece of electrical equipment to be used for measuring voltages across an unknown material, there often ends up being a lot of wiring in the probe as well as the bit at the end of the instrument that you are actually interested in. Some of this has a practical purpose. Often we want to measure something when it is very cold so it has to be on the end of a metal rod that is inserted into a vat of liquid nitrogen or helium or that is held in a strong magnetic field. When designing the probe, the bits of wire leading to the interesting bit at the end of the rod can be almost as important to consider as the measuring bit itself.

To see why, perhaps you remember putting compasses around a wire carrying an electric current? As the electric current is switched on, the compass needles move indicating that the electrical current generates a magnetic field. The basis of electric motors and dynamos, the idea is that an electrical current will generate a magnetic field and a moving magnetic field would generate an electrical current.

transmission lines, electrical noise

The wires to the light bulbs in Frequency Kings Cross. Memories of transmission line lab experiments.

Now, imagine two parallel wires each carrying an electrical current. Both of them will produce a magnetic field, but if there is a varying current in one or other of the wires, the magnetic field will also be varying. And if there’s a varying magnetic field, it can induce a current in the neighbouring wire. In this way, electrical noise on one of the wires can be transmitted to the other.

Such electrical noise can be inconvenient if we are trying to speak on the phone and just hear a ‘hiss’, or if we are trying to listen to the radio and just can’t tune in. It could also be more problematic, imagine if there was a lot of electric noise on a machine measuring the electrical activity of your heart, an ECG. Consequently, there are whole books written on how to reduce electrical noise pick up. However one simple way to reduce a lot of the noise is to get rid of those parallel lines the like of which are on the ceiling at Frequency by twisting them together. The ‘twisted pair’ is a great way of making more sensitive electrical measurements. And if you wanted to reduce the noise further, you can shield the twisted pair with another conductor and ground (or earth) it.

The twisted pair works by reducing the magnetic coupling between the two wires. Of course, it may not be quite as immediately aesthetically pleasing as parallel wires on a ceiling but there is something quite elegant about a well made and shielded twisted pair properly grounded in an electrical circuit. And when you put everything together, ground it properly and see the noise from the electrical mains (at 50Hz) disappear, there is a certain pleasing effect from that too.

Café design as a clue to electrical design. Frequency can be found at 121 Kings Cross Road, WC1X