Category: Tea

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Coffee review General Observations slow Sustainability/environmental Tea

Environmentalism inside and out at Farmstand, Covent Garden

Farmstand Drury Lane
Farmstand on Drury Lane

How can we live sustainably, buying locally, being mindful of our ecological footprint and still drink coffee? A recent trip to Farmstand on Drury Lane revealed a café conscious of its environmental responsibilities, somewhere that is trying to help us to make a difference while still enjoying good food and great coffee. Is it possible for us to have our coffee and drink it? The people behind Farmstand certainly seem to think so.

The bare brick walls inside the spacious Farmstand have a certain rustic charm that serves to emphasise the environmental concerns of the café. A focus on local, free range meat and GM free vegetables means that this is definitely a place to be considered when looking for a lunch spot (though on this occasion, we only tried the coffee). Coffee is obviously not locally grown but is roasted by Workshop which is, relatively speaking, just down the road. Tea meanwhile comes from Postcard teas, just up the street. Water is complementary and is provided on tap so as to reduce plastic waste. The service was friendly and with such a bright and airy feel it is a very pleasant space to enjoy an Americano (though I imagine it is fairly crowded at lunchtimes). However, the Americano was served in a take-away cup (when I specified I was staying in). After a bit of digging on their website, I discovered that they use compostable and/or recyclable packaging sourced from London Bio Packaging. However, as it is not easy to either recycle nor to compost cups in regular waste collection (including recycling collections), it would be interesting to know details of how they dispose of their cups so as to know how they reconcile this with the otherwise careful environmental policy.

Interior vertical gardening
Green wall inside Farmstand

As you enter the café, there is a staircase on the left hand side. Potted plants are fixed to the railings making what seems to be almost a miniature green wall. A great way to get houseplants into a small space, this seemed a small scale example of the green walls that are starting to pop up around our cities. Green walls are vertical gardens. They can be grown either with climbing plants or with a second structure on the wall that supports the hundreds of plants. Along with an aesthetic appeal (certainly true of the structure at Farmstand), these green walls have environmental benefits too.

A big environmental problem in cities is particulate pollution from exhausts. Specifically, particulate matter that is less than 10 μm diameter (think Turkish coffee grind) can irritate the lungs and cause health problems for the city’s inhabitants. Particulates less than 2.5 μm diameter are even more dangerous to health. Worldwide, in 2012, 3.7 million early deaths were associated with poor air quality. In London, a 2010 study showed that approximately 4000 deaths per year were the result of exhaust fumes. Which brings us to the first reason that green walls in cities may be such a good thing: Plants adsorb the pollutants.

Green wall Singapore
A green wall at the Ocean Financial Centre in Singapore, Image shared under cc license (attrib. share alike) by smuconlaw.

Over a three month period, a study by Imperial College showed that a single green wall on Edgware Road tube station had removed 515 g of particulate matter from the atmosphere. Using a mix of plants on the wall was found to increase the air turbulence around the wall and so increase the adsorption of the pollutants. Of course, different plants performed differently (in terms of their ability to remove particulate matter from the air). One of the plants on the wall (Convolvulus cneorum) could take out up to 2.73±0.16 g/m² of particulate matter*. On the other hand, another plant on the wall (Hedera helix) took out much less, removing only 0.28±0.02 g/m². However, we know Hedera helix by another name: Ivy. And ivy plants can produce a lot of foliage per plant very quickly. Convolvulus cneorum on the other hand, is a small plant with small leaves. While its efficiency could be very high, the amount of pollution it can remove may not be as great as an ivy plant, purely as a consequence of its leaf size.

Which brings us to questions of aesthetics and practicality. The wall at Edgware Road is planted with many different types of plant in order to produce an effect that reduces pollution while also being good to look at. Similar walls have sprouted up all over the world. However, for short term projects that require a large amount of foliage quickly, planting ivy can be a good option as a pollutant remover. Some of the temporary structures built along Park Lane for the Crossrail project are now covered with ivy. Although I had initially thought that this was due to a lack of weeding, it turns out that this is part of a step towards pollution reduction in our cities (modelling data has indicated that these green walls can reduce the local particulate pollution by 10-20% depending on the geometry of the wall and the plant species growing).

A small step perhaps, but one that is definitely in the right direction. The green wall at Farmstand could therefore be said to illustrate the idea that if we are to make a difference to our external world, we must start by reforming our own interior one. We need to make green walls not green wash and we can start by paying attention to what we plant inside and out.

Farmstand is at 42 Drury Lane, WC2B 5AJ

*The study looked at particulate matter between 2.5 µm and 10µm diameter (i.e. PM(2.5)-PM(10)).

 

 

Categories
General Home experiments Observations Science history Tea

Coffee and Pluto

Three billion miles away, on an object formerly known as the planet Pluto (now sadly demoted to the dwarf planet Pluto), there exists a plain of polygonal cells 10-40 km across, extending over a region of about 1200 km diameter. Last year, the New Horizons mission photographed this region and these strange shapes (see photo) as the probe flew past Pluto and its moon Charon. But what could have caused them, and perhaps more importantly for this website, can we see the same thing closer to home and specifically in a cup of coffee? Well, the answer to those questions are yes and probably, so what on Earth is happening on Pluto?

Plutonian polygons
What is causing these strange polygons on the surface of Pluto. Image © NASA

Pluto moves in an highly elliptical orbit with an average distance to the Sun of 5.9 billion km (3.7 billion miles). Each Pluto year is 248 Earth years but one day on Pluto is only 6½ Earth days. As it is so far from the Sun, it is very cold on Pluto’s surface, somewhere between -238 to -218 ºC. The polygons that were photographed by New Horizons are in the ‘Sputnik Planum’ basin where the temperatures are at the lower end of that scale, somewhere around -238 ºC. At this temperature, nitrogen gas (which makes up 78% of the Earth’s own atmosphere) has not just liquified, it has solidified; turned into nitrogen ice. These polygons are made of solid nitrogen.

But solid nitrogen is a very odd type of solid and in fact, at the temperatures on Pluto’s surface, solid nitrogen is expected to flow with a very high viscosity (like an extremely gloopy liquid). And it is this fact that is the clue to the origin of the odd polygons (and the link to fluids like coffee). Pluto is not just a cold dead rock circling the Sun, but instead it has a warm interior, heated by the radioactive decay of elements in the rocks making up Pluto. This means that the base of the nitrogen ice in the Sputnik Planum basin is being heated and, as two groups writing earlier this summer in Nature showed, this leads to the nitrogen ice in the basin forming convection currents. The warmer nitrogen ‘ice’ at the bottom of the basin flows towards the surface forming convection patterns. It is these nitrogen convection cells that appear as the polygons on the surface of Pluto.

Rayleigh Benard cells in clouds
Rayleigh-Benard cells in cloud structures above the Pacific showing both closed and open cell structures. Image © NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response

Of course, convection occurs in coffee too, we can see it when we add milk to the coffee and watch the patterns form or by observing the dancing caustics in a cup of tea. So why is it that we see stable polygons of nitrogen on the surface of Pluto but not coffee polygons on the surface of our coffee? The first point to note is the time-scale. Although the polygons on Pluto are moving, they are doing so much more slowly than the liquid movement in a cup of tea or coffee, at a rate of only a few cm per year. But secondly, the type of convection may be different. Although both of the papers in Nature attributed the polygons on Pluto to convection, they differed in the type of convection that they considered was happening. McKinnon et al., suggest that the viscosity of the nitrogen on Pluto is much greater on the surface of the basin than in the warmer interior and so the surface flows far more slowly. This leads to cells that are much wider than they are deep. We would not expect such a drastic change in the viscosity of the coffee between the (cool) top and (warm) bottom of the cup! In contrast, Trowbridge et al., think that the cells are Rayleigh-Bénard convection cells,  circular convection cells that form such that the cells are as wide as they are deep. This sort of convection is seen in a coffee cup as well as in the sky on cloudy days: On the Earth, clouds often form at the top (or bottom) of Rayleigh-Benard cells, where hot humid air meets cold dry air (more info here). But to form cells that you can see in your coffee (such as are on the surface of Pluto) you would need the coffee to be in a fairly thin layer and heated from below. You would also need some way of visualising the cells, either with an infra-red camera or with powder suspended in the liquid, it would be hard I think to see it in coffee alone. However, you can see these cells in cooking oil as this video shows:

As well as providing the link to the coffee, the different types of convection on the surface of Pluto hypothesised by Trowbridge and McKinnon have consequences for our understanding of the geology of Pluto. If the cells are formed through Rayleigh-Bénard convection (Trowbridge), the basin has to be as deep as the cells are wide (meaning the basin has to be 10-40km deep with nitrogen ice). If McKinnon is correct on the other hand, the basin only needs to be 3-6 km deep. It is easy to imagine that an impact crater could cause a shallow crater such as that needed for McKinnon’s mechanism. A deeper crater would create another puzzle.

If you do manage to heat coffee (or tea) from below and form some lovely Rayleigh-Bénard cells while doing so I’d love to see the photos or video. Please do contact me either by email, Facebook or Twitter. Otherwise, if you just enjoy watching the patterns form on your coffee, it’s worth remembering that there could be an entire cosmos in that cup.

Categories
General Observations slow Tea

The process or the cup?

effect of motivation on experience of pleasure while drinking coffee
Are you a hedonist or a utilitarian when it comes to drinking coffee?

Which part of the process of making and drinking coffee do you enjoy most? How do you rate the importance of smell, taste, touch (even hearing and sight) to the enjoyment of the process of brewing your cup?

It appears that your answer to this question may well be affected by your motivation for drinking your coffee in the first place. Last year, a group of researchers from Switzerland published a study that investigated whether the reason that you drank coffee (i.e. either for sensory enjoyment or just for the caffeine kick) influenced your enjoyment of the experience of making and drinking the coffee.

The researchers looked at how the participants in the study rated their own levels of enjoyment and satisfaction as they progressed through four stages of making coffee.

  1. Water heating
  2. Jar handling*
  3. Cup preparation
  4. Cup drinking

The 60 participants were divided into two groups of 30, those who drank coffee for enjoyment (the hedonists), and those who drank for stimulation (the utilitarians). After checking that both groups of participants rated their levels of pleasure and satisfaction similarly before the experiment started (they did), the participants were repeatedly interrupted while they made their coffee and asked to rate their levels of enjoyment and the importance that they attached to different sensory experiences (smell, sight, touch etc).

Kettle drum at Amoret
A very enjoyable coffee, but which part of the process of making and drinking coffee do you enjoy most?

After stage 4, when both groups had finally managed to drink their coffees, both groups reported similar levels of enjoyment, satisfaction etc. The difference came in the process. Overall, the group that were drinking the coffee purely for stimulation found the experience of making coffee less pleasant than the group who drank coffee because they enjoyed it. Meaning, those that drank coffee because they liked the taste seemed to enjoy the entire process of making and then drinking the coffee more than those who were just looking for a pick-me-up. Moreover, the ‘hedonists’ also attached more importance to the satisfaction of the smell and the taste of the coffee than did the ‘utilitarians’. Interestingly though, vision played an important role throughout the whole process for both groups of participants.

So how much we enjoy the process of making coffee depends on why we are drinking coffee in the first place. What about you? How do you rate the time that you spend brewing your coffee (I think that we can extrapolate this to tea too)? Are you a hedonist, a utilitarian or somewhere in between and does it matter? Please share your thoughts either here, on FB, or on Twitter.

 

*The study was performed at the Nestlé Research Centre so presumably used instant, hence the ‘jar’. Does this affect the conclusions of the study for ‘speciality’ coffee drinkers? Are you a utilitarian speciality coffee drinker who nonetheless enjoys the entire process? Please share your thoughts in the comments section below.

Categories
Coffee review Observations Science history slow Tea

Pottering about in Wa cafe, Ealing

Wa cafe, Ealing, pottery, ceramic, bamboo spoon, glass tea pot
Coffee and tea at Wa Cafe, Ealing

There is something somehow inviting in the minimalism that greets you as you walk into Wa Café in Ealing. Behind the glass counter on your left are a series of colourful cakes along with pastries and buns containing more Japanese-style treats such as the Sakura Anpan (a roll filled with red bean paste). The drinks menu features the usual set of coffees with a more extensive tea menu serving different sorts of Japanese tea. We had a long black (which according to London’s Best coffee is from Nude), the Sakura Anpan and a pot of Hoji Cha (roasted green tea). The coffee came in a delightful ceramic cup with a layering in the interior of the cup reminiscent of rock strata of the Earth. The tea arrived in a pot together with a glass that seemed linked to the type of tea that had been ordered. Glancing around the cafe, it was apparent that different teas were served in differently shaped glasses. Was this due to the fact that glass shape can affect the perceived taste of wine and so maybe also tea?

The saucer for the coffee cup featured a carved pattern that, although different, reminded me of the medieval labyrinths that you can find (such as in Chartres Cathedral). But it was the individual style of the pottery that caused me to recollect a story I had discovered while researching a previous Daily Grind article (and then didn’t use at the time).  The story concerned a ship wreck just off the coast of Malaysia which was leading to a reassessment of our ideas about ancient trading routes and population migrations. As pottery is often one of the bits of the cargo that does not degrade significantly under the water, it is pottery that provides clues for some of our ideas about the past.

Wa_coffeecup
Drinking the coffee revealed ‘layers’ in the cup.

For this article on Wa Cafe though, a little digging revealed a recent archaeological discovery that involved not the pottery itself, but what had been in the pots. It had been known for some time that the first pottery found in Japan dated to about 16,000 years ago, and that around 11,500 years ago there was a significant increase in the volume of pottery produced. As this surge in pottery making was coincident with the end of the last ice age, it was thought that this increase in pottery production was driven by the availability of new sources of food as the climate warmed. So, it came as a surprise when the ‘charred surface deposits’ – meaning the bits of food left after cooking, found in the interior of the pots were actually analysed.

Using a general technique called mass spectrometry, the authors of the study investigated what elements could be found in the food deposits on the pots. They particularly looked at the ratio of carbon and nitrogen in the pots. The proportion and type of element in the food remains have been shown to indicate what had been cooked in the pot, whether it was meat, fish or vegetable matter. As the authors analysed the results they found that the pots were used for cooking fish, fish and more fish. From 16,000 years ago and on for a further 9000 years, the pots were used for fish. Although there was a shift towards the consumption of freshwater fish through the time period studied, there was not the significant change to meat and vegetable matter that had been expected prior to this analysis. The function of the pots had remained constant over millennia.

Labyrinths
A medieval labyrinth and the coffee saucer at Wa. It is thought that many labyrinths were used as meditative aids as you walked your way through them. What would you meditate on while drinking your coffee?

This suggests that rather than the increase in pottery production being about a change in function of the pot, the pots had a distinct cultural use that was unchanged through the warming climate. The results of the analysis challenge the preconceived ideas that had been previously been held. The full paper can be found here.

To an untrained and naive eye of course, I wonder if the people using these pots just had some odd recipes for fish. Maybe they made plenty of vegetable soup (which they rarely burned) but always chargrilled the fish in the pot leading to a prevalence of fish in the ‘charred surface remains’. Nonetheless, this is probably just a poor understanding of what the authors meant by ‘charred surface remains’, surely not every cook burns their fish!

Wa Cafe can be found at 32 Haven Green, W5 2NX

 

 

 

Categories
Coffee review General Observations Sustainability/environmental Tea

Reduce, Re-use, Recycle at Attendant

The outside of Attendant on Foley St
Attendant Coffee, Foley St

I was not initially going to do a cafe-physics review of Attendant. It wasn’t that I didn’t enjoy the coffee, I did. I had a very well prepared V60 which went very well with a lovely chocolate brownie. Nor was it that there was nothing to see at Attendant. No, it was quite the opposite. Part of the point of the Attendant seems to be its location. You see, if you were not aware of it already, Attendant is to be found in a (no-longer-used), underground, gentlemen’s toilet. Although they have been thoroughly cleaned, various fixtures (19th century urinals and cisterns) remain in place. Modern (deliberate) graffiti adorns the walls as you walk in. Understandably, there are no windows to gaze out of in this café. It is, in many ways, a very interesting place to visit and the coffee is certainly worth a visit too. However, it is difficult to do a review which is, after all, about noticing something unusual, when the former use of this space is almost shouting at you. I thought about doing a review based on how the shape of the coffee cup can influence the flavour of  the coffee that you perceive. Yet somehow, writing a review on anything other than the fact that this is a re-use of an interesting space seemed, almost, perverse. So I left it. Until that is, UK Coffee Week came along.

UK Coffee Week raises awareness and money for Project Waterfall which in turn aims to help provide clean water and sanitation for coffee growing communities. Currently, Project Waterfall works in three countries, Tanzania, Rwanda and Ethiopia. In these countries a large number of the rural population lack basic access to drinking water while a greater number do not have access to sanitation facilities. Clearly this can lead to health problems. The World Health Organisation estimates that world wide, the drinking water of 1.8m people is contaminated with faeces, while 0.5 million people per year die from diarrhoeal diseases including cholera.

Interesting glassware at the Attendant
Interesting presentation. Coffee at the Attendant.

Perhaps, while sitting in cafés or having breakfast at home, we have a tendency to take water for granted. Certainly I will admit that I can. I’m sitting here writing this enjoying a great cup of coffee with a few biscuits both of which took water to produce. Beyond the obvious water in the kettle for the coffee and the water used for the dough for the biscuits, there is the ‘hidden’ water. The water used to irrigate the coffee crops and the wheat fields or to process the coffee cherry towards the green bean stage. The water used in generating the electricity used to bake the biscuits, or roast the coffee. The water used to clean the utensils between coffee roasts/biscuit batches so that we don’t get food poisoning. The list could go on. Indeed, the UN estimates that producing 1 cup of coffee requires 140 L of water. This figure though presumably cannot include the private water needs of the individuals who work on the coffee plantations. We all need water and we all need it to be clean.

So, in thinking about our water consumption (and the water consumption of those who help us to enjoy our coffee), we can do a few things during this coffee week 2016. Firstly, we could make a donation towards the work of Project Waterfall (here) or a similar charity that is working to provide clean water and adequate sanitation to those who don’t have it. Secondly, we could take the prompt from Attendant and start to think about where our water comes from. Why from Attendant? Well if you were living on the International Space Station or, to a lesser degree, in Singapore, this question may have an obvious answer. For the rest of us, we are often a little bit removed from direct water recycling, but it’s worth looking more closely at Singapore because they have developed a water strategy that may be of use for more of us in the future.

Reclaimed water NEWater, Singapore
30% of water supplied in Singapore is ‘reclaimed’. Where does your drinking water come from?

Singapore has a population of just over 5.5m (London: 8.6m) with a land area of 719.1 km². As an island, it is surrounded by water and so you may think that water is not a problem for the inhabitants of the city-state. But the water surrounding Singapore is the salt water of the sea and so not easily converted into drinking water. While looking for a solution towards a self-sufficient water supply, Singapore decided to try the recycling route. Through a scheme called NEWater, currently 30% of Singapore’s water supply is from  ‘reclaimed’ water (for reasons that may be obvious, they avoid the word ‘recycled’). The Singaporean authorities aim to make this 55% by 2060. Waste water produced in Singapore undergoes a process of micro-filtration (which takes out suspended particles), reverse osmosis and UV disinfection before being reintroduced to the water supply system. Although most of this reclaimed water is used for industrial processes, the reclaimed water can be added to Singapore’s reservoirs so that it will go into the drinking water supply.

A similar process is used on the International Space Station but there, as it is a closed environment, it is not just the waste water that goes down the drain that is ‘reclaimed’ but the water exhaled by the astronauts and the lab animals on the station. On Earth this would evaporate into the atmosphere, contribute to cloud formation and then rain back down closing the greater water cycle in that way. On the space station, the fact that it is a closed environment means that this moisture too can be ‘reclaimed’. By recycling the water in this way, the inhabitants of the space station avoid having to require too many costly water deliveries from the Earth.

Perhaps, while drinking our coffee (or tea, or even water) today, we can take five minutes to consider where our water comes from as well as considering whether those who contribute to our brew have adequate water supplies themselves. And as it is coffee week, here is that link again to Project Waterfall (Donation button at the bottom of the main Project Waterfall page). Enjoy your coffee.

Note added August 2017: It is with some regret that I have to say that Attendant is not a good place to go if you suffer from allergies. They have started serving almond milk and (according to a Twitter Direct Message received from the Attendant Team) do not adequately clean their steam wand between drinks so as to prevent cross contamination. Their advice to me was that I “should not have any hot drinks or food at our premises as we do not operate a nut free environment at our stores”. There are many good cafes to visit if you suffer from nut allergies, but please avoid this one (or just have a black coffee and enjoy the atmosphere).

 

 

Categories
cafe with good nut knowledge Coffee review Home experiments Observations Tea

Electrifying coffee at the Black Penny

Black Penny coffee London
The Black Penny on Great Queen St

Back in the seventeenth and eighteenth centuries, coffee houses were places to go for debate, discussion or even to learn something new. The Grecian was known for science. Maths instruction (particularly for gambling) could be found with Abraham de Moivre (1667-1754) at Old Slaughter’s on St Martin’s Lane. Other coffee houses were meeting centres for literature, politics, philosophy or even espionage*. Coffee houses became known as “Penny Universities”. The Black Penny on Great Queen St is a café that wants to continue this tradition, with a downstairs “seminar pit” ready to host such discussions. Although the events page still says “coming soon”, if the events do indeed come, this is very much something that’s worth keeping an eye on.

Even without the seminars though, The Black Penny is definitely worth a visit. Entering from the street, the bar is on the left and is stocked with a good looking selection of cakes. We were shown through to the relatively large, bright and airy seating area at the back where a jar of water (infused with cucumber and mint) had been put on the table for us. I had a very good long black and a lovely apple and blackberry muffin with which to take in my surroundings. The muffin was confidently asserted to be nut-free, and so the Black Penny gets a tick in the ‘good nut knowledge’ section on the Daily Grind. The coffee beans were roasted by the Black Penny themselves and while it still says that they serve ‘Alchemy’ coffee on their website, this no longer appears to be the case.

Duracell batteries as coat hooks, battery, batteries
A strange form of coat hook? The things that catch your eye in cafes

Inside, there are some very interesting architectural features to notice, the remains of a ceiling for example (now removed to reveal the roof) and the acoustics introduced by the speaker positioning. Downstairs in the seminar pit there is apparently a very old stove, though I didn’t get to see that on my visit. However, what immediately struck my eye was what appeared to be a series of coat hooks that looked very similar to a well known brand of battery. Quite what these hooks were for or why they looked like batteries I didn’t manage to ascertain, however, it did get me thinking, can you use coffee-power to light an LED?

You may have heard of a potato battery, or a lemon battery. These are often used in science outreach experiments in schools to demonstrate electricity, or the concepts of current/voltage. Made from an ordinary potato (or a lemon), a copper wire is stuck into one end of the potato and a different metal (usually zinc) is stuck into the other end of the potato. At the Black Penny, there were three things left on the table. My coffee, the mint and cucumber infused water and the tea of my accomplice in many of these reviews (I’d eaten the muffin). Which of these would perform better as a battery?

coffee power
Can 6 coffee ‘cells’ with aluminium and copper electrodes light up an LED? (The answer may be in the photo)

Although people suggest using galvanised screws as the source of the zinc electrodes, I didn’t have many of those to hand and so had to manage with aluminium foil for one electrode, copper wire for the other. By putting the aluminium on one side of a shot glass, the copper wire on the other and then filling the glass with coffee, I was able to get 0.5-0.8V across the electrodes when I measured it with my digital multimeter (DMM). Fantastic you may think, almost an AA battery, but then if you were to measure the voltage across the water rather than coffee, you will find that you get a voltage of 0.6-0.7V. The result for tea was, perhaps unsurprisingly, about 0.6V.

But voltage is not the whole story. A battery does not just supply a voltage, it gives a current. The current depends on the electrical conductance of the liquid that the electrodes are in. In the case of the potato or the lemon battery, the acid (phosphoric or citric respectively) means that there are free hydrogen ions in the ‘battery’ between the electrodes which mean the electric current can flow through the circuit. Coffee consists of many acids (chlorogenic, quinic, citric etc etc.) and so it seems sensible to ask if coffee could be used to produce a battery with a current that could power an LED? LEDs require both voltage and current, (1.6V and 10mA for the LEDs used here). Hooking up a series of coffee battery-cells meant that, by 6 ‘cells’, I had 3V across the contacts. However the electric current through the coffee battery was very low (the maximum current I recorded using the low acidity Roasting House Sierra de Agalta Honduran coffee prepared in a cafetière was 155 μA). Although this was higher than the current through water (max 81 μA), it is much lower than the current through white vinegar (770 μA under the same conditions). Consequently, in order to light the LED connected to my coffee battery, I had to add salt to each coffee cell which serves as a way of massively boosting the current through the coffee (salt forms a solution of Na+ and Cl- ions that conduct electricity through the coffee). Though even then, my LED only lit dimly and intermittently.

battery, Volta, Como museum, Como
How it should be done. The “Alessandro Volta Temple” in Como, Italy, is a fantastic place to learn about the history of electricity

Sadly then, I do not see coffee power as a future for lighting in our cafés, (unless you want to use bulletproof coffee with salted butter). However, it has started to make me wonder, could we use a single coffee-cell to monitor the acidity of our coffee? If you find a method of brewing or a particular coffee especially acidic, it should produce a higher current for the same voltage through the cell, or equivalently, the resistance of the coffee-cell should decrease as the acidity of your coffee increases. Although obviously, it would be a bad idea to drink the coffee after putting it into a cell with copper and zinc (or aluminium) electrodes, you could pour a small amount of your coffee into a shot glass to test it while you were drinking the rest of the coffee. I intend on testing this hypothesis over the next couple of weeks but in the meanwhile, if you have thoughts on this to share (or the results of your experiments), please let me know either via the comments section, email, Facebook or Twitter.

The Black Penny is at 34 Great Queen St, WC2B 5AA

* A history of coffee houses can be found in “London Coffee Houses”, Bryant Lillywhite, (1963)

 

Categories
General Observations slow Tea

Happiness is a cup of coffee

stone recycling, slate, slate waterfall, geology
A cafe with a lovely space to enjoy the coffee. Taking time out at Espresso Base

If you are reading this, you clearly have access to a computer. You are also quite possibly connected through social media to friends, colleagues and others through Facebook, Twitter, Instagram or one of the other numerous ways in which we can now connect with each other. And while I would love for you to continue reading, at least for a couple of moments, I would like to ask you how often you take the opportunity to stop?  To stop and turn off your computer or the notifications on your smart phone and just look at what is around you.

This website is really about slowing down and noticing things. Since I believe that science offers a great way of seeing the connectedness of the world around us, I choose to emphasise the science that you can notice around you. It is most likely that you see the world in a different way, sharing some aspects of my point of view, disagreeing with others. However, it seems to me that slowing down and noticing your surroundings, whether you look at the science or another aspect of those surroundings, makes us in some way happier, or at least, generally, more calm. Having a coffee in a café is a great way of doing this. Whether you are interested in the café or the coffee (or indeed both), there is an awful lot to notice and to appreciate in a café. Noticing it of course does depend on keeping the smartphone (tablet or laptop) in your pocket or your bag. Personally, I find it slightly depressing when I see signs in a café saying “free wifi” (though I suspect I am in a minority on that one). And although if we are not used to it, not checking our email while having a coffee can seem to be enforced boredom, I’d hope that we soon realise that such boredom is in fact creative.

Sun-dog, Sun dog
Walking along while texting could mean that you miss seeing a sun dog

Please don’t get me wrong. It is not that I think social media are a bad thing. I have met (either ‘virtually’ or in person) some great and highly interesting people whom I would never have had the opportunity to meet were it not through Twitter/Facebook etc. Each day, I learn something new through the many people whose experience or knowledge I would otherwise never have had the opportunity to ‘tap’. However, just as sometimes it is great to have such interactions, I have found that it is also vital to have times (perhaps even a day a week) when the smartphone is kept firmly in the pocket (or at least, notifications are turned off).

In the UK, we have just got back from a long weekend. Many cafés were closed over the Easter break. Some of the café-Twitterers I follow went on a long break to the countryside (and Tweeted about it), others just turned off their social media for a few days. Elsewhere in the world you perhaps have different long weekends, Chinese New Year or Christmas. Perhaps during these holidays you manage to get a break in the countryside or by the coast. It is here that there is a link between an interesting recent study and a great use of a smartphone.  The study, by researchers at the University of Surrey and the London School of Economics, attempts to measure your ‘happiness’ while you are undertaking different activities in different locations, in urban environments, at work, or bird watching in the country.

Another great coffee outside, this time at Skylark cafe
Another great coffee outside, this time at Skylark cafe

Called the ‘mappiness‘ project, an app downloaded onto your iPhone (it is, sadly, only for iPhones), prompts the user to answer a question about their own perceived level of happiness at random instants. It then records the location of the phone (through GPS) and further asks the user to describe what they are doing. Over 1 million responses have so far been recorded through 20 000 participants. Perhaps unsurprisingly, the researchers have so far found that people tend to rate their happiness higher when they are outside, in natural environments and particularly in coastal areas. To me, it opens questions as to whether we should be attempting to quantify happiness or whether we should embrace the discussions of the humanities on this issue (less precise perhaps but by that very fact more complete and therefore more accurate). Perhaps these two approaches are complimentary. Nonetheless, the mappiness project remains an interesting study of a way in which you can use your phone in order to get a measure of where you should use your phone less.

Do get in touch and let me know what you think. Do you find it necessary to have some time out from social media or is Facebook your lifeline? Should cafés offer free wifi? Comments are always welcome (below) or you can get in touch by those two social media sites Twitter or Facebook. I do look forward to interacting with you there.

 

Categories
General Observations slow Tea

Tea Gazing

Milky Way, stars, astrophotography
The Milky Way as viewed from Nebraska. Image © Howard Edin (http://www.howardedin.com)

A recent opinion piece about last week’s announcement of the detection of gravitational waves at LIGO drew my attention to a quote from Einstein:

“The most beautiful experience we can have is the mysterious. It is the fundamental emotion that stands at the cradle of true art and true science. Whoever does not know it and can no longer wonder, no longer marvel, is as good as dead, and his eyes are dimmed.“

Einstein was not the only scientist to have expressed such sentiments. Many scientists have considered a sense of wonder to be integral to their practice of science. For many this has involved gazing at the heavens on a clear night and contemplating the vastness, and the beauty, of the universe. Contemplating the twinkling stars suggests the universe outside our Solar System. Watching as the stars twinkle gives us clues as to our own planet’s atmosphere. Of course, it is not just scientists who have expressed such thoughts. Immanuel Kant wrote:

“Two things fill the mind with ever-increasing wonder and awe, the more often and the more intensely the mind of thought is drawn to them: the starry heavens above me and the moral law within me.“*

light patterns on the bottom of a tea cup
Dancing threads of light at the bottom of the tea cup.

The other evening I prepared a lovely, delicate, loose leaf jasmine tea in a teapot. I then, perhaps carelessly, perhaps fortuitously, poured the hot tea into a cold tea cup. Immediately threads of light danced across the bottom of the cup. The kitchen lights above the tea cup were refracted through hot and not-quite-so-hot regions of the tea before being reflected from the bottom of the cup. The refractive index of water changes as a function of the water’s temperature and so the light gets bent by varying amounts depending on the temperature of the tea that it travels through. Effectively the hotter and cooler regions of the tea act as a collection of many different lenses to the light travelling through the tea. These lenses produce the dancing threads of light at the bottom of the cup. The contact between the hot tea and the cold cup amplified the convection currents in the tea cup and so made these threads of light particularly visible, and particularly active, that evening. It is a very similar effect that causes the twinkling of the stars. Rather than hot tea, the light from the distant stars is refracted by the turbulent atmosphere, travelling through moving pockets of relatively warm air and relative cool air. The star light dances just a little, with the turbulence of the atmosphere, this way and that on its way to our eyes.

Marcus Aurelius wrote:

“Dwell on the beauty of life. Watch the stars, and see yourself running with them.“†

Marcus Aurelius of course didn’t have tea. Watch the dancing lights in the tea cup and see yourself sitting with it, resting a while and then watching while dwelling on the beauty in your cup.

*Immanuel Kant, Critique of Practical Reason

†Marcus Aurelius, Meditations

Categories
General Home experiments Observations Science history Tea

Caustic Coffee

A post that applies equally to tea, just swap the word “tea” for “coffee” throughout!

A cusp caustic in an empty mug of coffee
Have you seen this line?

Look deep into your coffee. Do you see the secrets of the cosmos being revealed? Well, neither do I usually but there is something in your coffee that could be said to have ‘cosmic implications’ and I’m sure it’s something that you’ve seen hundreds of times.

Now, admittedly it is easier to see this effect if you put milk in your coffee. Imagine drinking your (milky) coffee with a strong light source (the Sun, a lightbulb) behind you. You see that curved line of light that meets in a cusp near the centre of the cup? You can see various photos of it on this page. Yes, it is indeed the reflection of the light from the curved mug surface but it is far from just that. It is what prompted a professor at Duke University to say “It’s amazing how what we can see in a coffee cup extends into a mathematical theorem with effects in the cosmos.” To understand why, perhaps it is worth reflecting a bit more on our coffee.

The shape of the curve is called a ‘cusp’  and the bright edge is known as a ‘caustic’. It is fairly easy to play with the angle of the cup and the light so that you can see the first cusp curve but you can go further and create caustics that are the result of multiple reflections. Such multiple reflections can give heart shaped curves or “cardioids” so, in a certain sense adding milk to your coffee is good for (seeing) the heart.

caustic in a cup of tea or coffee
A cusp reflection is just visible in a cup of (soya) milk tea

Caustics were first investigated by Huygens and Tschirnhaus in the late 17th century. Mathematically, the cusp curve is termed an epicycloid, you can draw one by tracing the shape made by a point on the circumference of a circle rotating around a second circle, as this graphic from Wolfram mathematics demonstrates. There is a lot of maths in milky coffee. But just how is it that these curves reveal the “Cosmos in a cup of coffee“? It turns out that once you start to see caustics you start to see them everywhere. Caustics are not just going to be formed on the inside of your coffee mug, they can be formed by light waves getting bent by ripples on the surface of a stream or even by gravity, in a phenomenon known as “gravitational lensing”.  Gravitational lensing is when a massive object, such as a black hole or a galaxy, bends the light travelling past it so that it acts analogously to a lens in optics (but a very big one). It is this last type of caustic that prompted the headline quoted above. In a series of papers published in the Journal of Mathematical Physics, Arlie Petters of Duke University and coworkers calculated how light from distant objects was focussed through gravitational lensing and the effects of caustics. Their predictions (and in particular any exceptions to their predictions) could lead to a new way to search for the elusive dark matter, which is thought to contribute to much of the Universe’s mass. They are now waiting for the Large Synoptic Survey Telescope (LSST) to start mapping the sky in order to test their theories.

multiple caustics from multiple LEDs
Multiple light sources are being reflected in this cup.

Before concluding this discussion of cosmic coffee, it is worth taking another look at the mathematician Tschirnhaus. As well as maths, he was known for his philosophy and his chemistry. In fact, it seems that he was responsible for the invention of European porcelain. As noted elsewhere, it has been argued that it was the ability of Europeans to start making their own porcelain that explained the rapid rise in consumption of tea and coffee during the eighteenth century in Europe. Interestingly, one of the tools that allowed Tschirnhaus to succeed in manufacturing porcelain in Dresden where others elsewhere failed was his use of “burning mirrors” to focus the heat and to achieve higher furnace temperatures than were otherwise available. He was using those caustics that he and others had so thoroughly studied mathematically in order to produce the type of cup in which we most often encounter the easiest caustics. A lovely little ‘elliptical’ story on which to end this Daily Grind.

In order to see the caustics in your coffee, it is necessary that the coffee reflects the light incident on it. Meaning, you need to add milk to your coffee. I knew there had to be a good reason to add milk to coffee at some point. Please do share your photos of caustics in your coffee either here or on Facebook or Twitter.

 

 

Categories
General Home experiments Observations Tea

Bouncing Coffee

floating, bouncing drops
Water droplets ‘floating’ on a bath of water (actually they bounce rather than float).

Perhaps you remember the video about how to ‘float’ coffee droplets on water posted on the Daily Grind a few weeks ago? The video featured an experiment that you could do at home in which droplets of water (or coffee, or even, if you were feeling adventurous, tea) could be made to stay as spherical droplets on the surface of a shallow dish of water for minutes at a time. Of course there were a few tricks: The water had soap added to it (10ml of soap to 100ml of water) and the shallow dish was on a loudspeaker which was playing music at the time. The whole experiment was very pretty. But hopefully as well as appreciating the aesthetics, you were asking ‘how’ and ‘why’? Why does the addition of soap mean that these globules of liquid appear to float on the liquid surface? And is the rumour you have heard about a connection with quantum physics true?

Well it turns out that people have known about these floating droplets for over a hundred years but why they behave as they do is still being investigated. It is another case of cutting-edge science appearing in your coffee cup*. So it’s worth taking a look at what is going on and why we needed to add soap and vibration for the droplets to remain stable on the water surface.

lilies on water, rain on a pond, droplets
When it rains, the rain drops don’t float on the pond

It seems to appeal to common sense and to everyday experience that if we drop a droplet onto a bath of water, the droplet will merge with the water and become part of the bath. After all, when we bring two drops that we have dripped on a table close to each other, at a certain distance between the two drops, they appear to touch and then rapidly merge into one big droplet (try it). And when it rains onto a pond, we don’t see lots of spherical droplets hovering over the surface of the pond! We know that it is the attractive van der Waals forces that bring the two drops together and then the effects of surface tension that minimise the surface area of the drops so that they become one big drop. So how is it that we can get a droplet to remain, as a droplet, on the surface of a bath of water?

How to bounce water droplets on a water surface

It could be said that the answer can be pulled out of thin air: Before the drops can merge, the air that separates them has to escape from the area between the droplet and the water bath. If the droplet can somehow be made to bounce back upwards before the air separating the droplet from the bath becomes thin enough for the two liquids to combine, the air could be made into a cushion to keep pushing the droplet upwards. This is why the experiment needs to be done with a vibrating dish of water, each time the surface vibrates upwards it is providing the drop with an acceleration upwards that overcomes gravity, like a miniature trampoline: The droplet is not floating, it is bouncing.

So why soap? We all know that the addition of soap decreases the surface tension of the water. But that is not why the addition of soap helps to stabilise the drops in this instance. No, soap has another effect and that is to increase the surface viscosity (and surface elasticity) of the water. Think about the air between the droplet and the dish. As the droplet bounces down (ie. the distance between droplet and water becomes a minimum), the air gets squeezed out of the layer between the droplet and the bath. On the other hand, as the droplet reaches its peak height, air will rush into the gap between the drop and the bath. If the liquid is not very viscous (eg. water), as the air rushes in (or gets squeezed out), it will combine with the liquid and form a turbulent layer on the surface of the droplet. If the viscosity is increased, the air cannot ‘entrain’ the liquid as the droplet bounces and so the drop keeps its shape more easily and is more stable. Soap increases the surface viscosity of the droplet and so helps with this effect. However soap also increases the surface elasticity and makes it harder for the air to flow out of the layer separating the drop from the bath. It is because soap does multiple things to the water (or coffee) that more recent studies have focussed on liquids with controllable viscosity but minimal surfactant effects, i.e. silicone oils. It is just that if you want it to work with coffee, it is easier to add the soap to get the experiment to work.

An “un-cut” video of coffee on water shows how tricky it can be to actually get these drops to be stable on the surface of the water.

Which leaves the quantum link. The experiment shown in the videos show single droplets (or droplet patterns) stabilised by vibrations caused by music. If instead of music you use fixed frequencies to excite resonances through the speakers, it is possible to get the droplet to resonate in a controlled way and, at a certain point, it will move. As the droplet moves, it appears to be guided by the vibrations of the liquid underneath the drop, it is a particle guided by a ‘pilot wave’. It turns out that such walking droplets show behaviour reminiscent of the ‘wave particle duality‘ found in quantum physics where particles (such as electrons and other sub-atomic particles) can be described both as particles and as waves. You can find a video describing the similarities between these bouncing droplets and quantum effects here.

 

* Ok, so you may not want to add soap to your coffee to see this effect but actually I first observed it in a milky tea. Adding milk to the coffee/tea would increase its viscosity which makes the observation of the bouncing droplets more likely. The ‘milk’ used in the video was actually soya milk which did not appear to increase the viscosity sufficiently to allow the droplets to bounce on the surface without soap.