Category: Tea

Categories
Observations Science history Sustainability/environmental Tea

A language problem?

Bob Ward, Obama quote, climate change
The last generation: our urgent need to communicate effectively.

“The beverage was prepared by pushing water (at 94ºC and 1.0 MPa) through a pellet of coffee beans ground to an average of 10 – 100 μm diameter. The pellet had been compacted (“tamped”) using a variable pressure as described in ref [1]. Following a manual transfer of the cup to the table, the drink was consumed at a temperature of 55ºC. Fruity overtones were noted.”

Would you rush to try this coffee?

Last week I wrote about the effects of climate change on coffee and how climate scientists are trying to reach out and communicate more about the science behind global warming. But there was a crucial question left un-answered, just how do we communicate? Do we all speak the same language or is the dry impersonal prose of science a hindrance to discussion?

To start with the encouraging news. It turns out that scientists are a pretty trusted bunch. In a recent survey 79% of the British public trusted scientists to tell the truth (compared with 21% for politicians). Part of the problem for politicians may be the language that they tend to use, “if I am honest…”, “to be fair…” etc, are apparently statements that haemorrhage trust. These are not statements that you will hear made by scientists. The language of science is cold and dry, utterly devoid of the personal. So, coupled with the results of the survey, it is tempting to think that we should continue to use our cold and impersonal language when communicating things like climate change. It seems that this works.

Steam, scattering, colour
How would you describe your coffee? Do those who read your description read it in the sense that you wrote it?

Only we would be wrong, the language that we use is (apparently) not helping us to communicate and we need to change it (as the meeting was told in an impassioned talk by Bob Ward). An average scientific paper for example is designed to convey exactly what we did, how we did it and to eliminate any possible element of confusion. Ideally, we would write a scientific paper so that someone else could read it, understand precisely what we have done and repeat the experiment under very similar conditions. In this context, our dry language can work very well but does it work generally when communicating results more widely?

To see the problem, compare the (scientifically written) coffee review that started this article with an extract from a recent review of Silhouette Cheapside by Brian’s coffee spot:

“The coffee offering’s simple: there’s a single-origin espresso from Notes, a Brazilian Cachoeirinha during my visit. As an espresso this was gorgeous: fruity and complex, it rewarded me with every sip, holding its own right to the end. I also tried it as a flat white, which was very smooth and surprisingly different, the coffee and milk perfectly complimenting each other.”

A visit to Cheapside may be imminent.

So this is the problem, while the scientific language may convey accurately what was consumed, it can’t convey it fully. Language that communicates more generally includes details about how we feel: “gorgeous”, “rewarded me with every sip”, “surprisingly different”. The language used in Brian’s coffee spot in no way detracts from an accurate description of the espresso or the flat white. Arguably your idea of the drinks that Brian sampled at Silhouette is far better formed in your mind than the idea of the espresso described by the scientific-language description at the start of this post. Can we extend this reasoning to scientific descriptions of the science of climate change and its likely effects?

Earth from space, South America, coffee
Our common home.
The Blue Marble, Credit, NASA: Image created by Reto Stockli with the help of Alan Nelson, under the leadership of Fritz Hasler

Perhaps you could imagine yourself in the position of a climate scientist: your research is showing you that the planet that you live on is likely to suffer significant change as a result of something that we humans are doing but can also do something about. I would guess that you are likely to get quite worked up about it. Wouldn’t it come across better if scientists were to use some of that emotion in how they communicate? Wouldn’t it convey our meaning more effectively?

Immediately though we come up against this issue of trust. Does the cold and dry scientific language somehow better communicate that the argument is evidence based? In this line of reasoning, subjective descriptions would be ok for things like describing a good coffee but not ok for describing climate change. And yet I can’t help feel that even here there is a problem. The philosopher of science Michael Polanyi argued that “Fairness in discussion has been defined as an attempt at objectivity, i.e. preference for truth even at the expense in losing force of argument”. Our “preference for truth” must include the fact that we have an emotional investment in the argument. It is our planet that we are destroying. Indeed, attempts to hide this emotional investment may even lead others to suspect climate scientists of other, more nefarious, secondary motives (financial gain, global conspiracy). However there is an important caveat on Polanyi’s argument, he writes: “[f]airness and tolerance can hardly be maintained in a public contest unless its audience appreciates candour and moderation and can resist false oratory…”.

screenshot of tweet from Digitalnun
A thought provoking tweet from @Digitalnun – science communication goes both ways.

Which brings me to a last point. A recent tweet by Digitalnun posed a question on related lines: does careless reading or careless writing lead to more problems? What we write is not necessarily what people read and if we allow emotion to enter into the cold language of science then we may increase the likelihood of misinterpretation (whether deliberate or not). Will those who read our attempts to communicate science with full honesty be able to resist false oratory, twisting our words to imply a ‘war’ or financial interest? Which is more appropriate, to remain dispassionate and potentially unconvincing or to be more honest in our discussion at the possible expense of losing trust? It’s not a question which seems to have an easy answer. What do you think? Do scientists have a language problem? Would you trust a discussion on climate change more or less if you thought that the scientist actually cared about the planet too? Let me know, either in the comments below, on Facebook or on Twitter.

[1] is hyperlinked above but if you are in the habit of scrolling down to look at the references, you can find the article about tamping in “coffee research” published here.

The Polanyi quotes are from “Science, Faith and Society” by Michael Polanyi, University of Chicago Press, 1964 (2nd edition)

 

Categories
Sustainability/environmental Tea

Talking about coffee and climate change

coffee cake Muni
Coffee and chocolate, both of which may be badly affected by climate change.

Last week the Royal Meteorological Society hosted an afternoon of talks and discussion titled “Avoiding Myth, Mayhem and Myopia: the challenge of climate science communication”. The meeting coincided with a social media campaign “#showthelove” which aimed to highlight something that you fear is at risk because of climate change. As coffee is definitely one of those things that is at risk (and indeed is already being affected by climate change), I went along to the discussion to see what is already being done to communicate climate science and also, what we can do as science communicators.

Although I do not research climate science (my research involves superconductors), there are many links between coffee and the climate: clouds of steam, turbulent movement, periodic waves in the cup and of course the greenhouse effect. Additionally, the risks that coffee faces from the effects of climate change are dire. Summarised in the most recent report of the Intergovernmental Panel on Climate Change (AR5), the risks to coffee are threefold, 1) from a warming climate 2) from more extreme weather events, 3) from pests that have increased due to (1) and (2).

Currently about 27million acres of the Earth’s land is used to cultivate coffee, most of which is grown by small scale farmers. The effects of warming mean that this area is going to decrease substantially. For us consumers this is going to mean a dent in our pockets but for the estimated 120 million people worldwide who depend on coffee growing for their livelihood, it is likely to be catastrophic.

room full of scientists and others, RMetS meeting, discussion time
A good crowd meant a lively discussion at “Avoiding Myth, Mayhem and Myopia”. What should we communicate about climate science and how?

The odd weather patterns that are going to be more common are also going to affect the coffee yield. Severe droughts are likely to happen more frequently (this year’s drought in Brazil has actually prompted the government there to consider importing (robusta) coffee beans). Moreover the combination of higher temperatures and greater rainfall that has been seen recently in Central America has ‘helped’ outbreaks of coffee rust while the berry borer beetle is also benefitting from the warmer climate worldwide (at the expense of the coffee crop).

Among climate scientists, the issues are clear (for the world rather than just for coffee). Climate change is already happening and it is caused by human activity in the form of greenhouse gas emissions. The problems are how to communicate this knowledge both to policy makers and industry and to the public so that we, as a society, can do something about it. What do each of these groups want to know and how best to reach them? There were discussions at the meeting about how to engage with politicians and to ensure that the message is properly transmitted so as to translate into action but for me (as a non-climate-scientist who drinks a lot of coffee), the interesting bit was about communicating with the public. In this sense it was great to see that the meeting had attracted a diverse audience with both Oxfam and the Green Party represented. Two questions dominated here: How is climate change affecting us now (/will affect us in the future)? And, what can we each do about it?

Bob Ward, Obama quote, climate change
The last generation: Bob Ward emphasising the urgent need for scientists to communicate effectively.

In terms of the second question, it seemed agreed that the best thing that we each can do is to reduce our carbon footprint. A concern echoed by the Society’s recent communiqué written with other professional bodies (that you can read here). Simple things like driving less or buying more efficient washing machines (or other household appliances when they need to be replaced) can make a difference. Of course, if you wanted to, you can have a go at calculating your carbon footprint using tools such as this guide by David MacKay (it is a lot easier than it may seem at first glance). It was this aspect of what ‘we’ can do that some audience members (including a Green Party representative) thought was a key thing that scientists working with the Royal Meteorological Society needed to communicate. Expect to hear far more about how you can make a difference.

In general, it seemed that there was a clear feeling that the scientists there wanted to communicate climate science and the science of climate change more insistently and more clearly. Indeed there was a rallying call for us all to increase our science communication by Bob Ward (the Policy and Communications Director at the Grantham Research Institute of the London School of Economics). But how should scientists communicate? Is there an intrinsic conflict between the language typically used by scientists and the urgency of the message? Should climate scientists use emotion in their discussions about climate change and what about issues of trust? All these are too much for this piece and so I shall leave those questions until next week, for now perhaps, it would be worth asking people who read this to suggest something that they are doing to reduce their carbon footprint, it doesn’t have to be much and it doesn’t need to be about coffee (though it would be nice if there were some coffee ideas) but please do share your ideas for reducing your carbon footprint, it is likely that they will be useful for others too.

Next week: Do we speak the same language? Is scientific language a help or a hindrance when it comes to communicating climate change?

Categories
Coffee review Observations Science history slow Sustainability/environmental Tea

Seeing the light at Cable Co, Kensal Rise

coffee in Kensal Rise, Cable Co
Cable Co, coffee in Kensal Rise

It was fairly late on a February afternoon that we came upon Cable Co on Chamberlayne Road, (opposite Kensal Rise station). With a fairly ‘industrial’ type look, there are plenty of tables at the edge (and in the window) of the café at which to enjoy your coffee. There are also plenty of coffees on offer. Although I had an Americano, I noticed (too late) that pour-overs were available. Coffee is roasted by Climpson and Sons. As it was late in the day, the remaining cakes in the display case all looked to be nutty (or at least likely to be nutty) and so, sadly, I had to wait until I got home for my slice of cake. It was good coffee though, even without the cake, but in a bit of novelty the coffee came ‘deconstructed’, so I got to add the amount of water that I preferred, a nice touch.

Golden light from the setting sun streamed in through the windows (which is a navigation clue & tells you which side of the road this café is on). The effect of the Sun was to bathe the café in light and to silhouette our fellow coffee imbibers making the café take on a film-like atmosphere. The light had another effect though. The steam rising from both the jug of water and my espresso became far more visible than it would normally have been. I watched as the steam clouds formed vortices and turbulent patterns, one fluid (steam) moving through another (air). It was very difficult to catch this in a photograph, a fact that I took in support of my idea that it is impossible to catch the beautiful, beauty is necessarily transient (but my companion in these reviews took as evidence in favour of their idea that I really ought to use a “proper”, manual, camera and not my iPhone).

Steam, scattering, colour
Steam rising from hot water, seen at Cable Co, Kensal Rise

Still, those turbulent rising patterns of steam were visible and that implies that light was being scattered from the droplets of water in the steam. The size of the droplets influences the colour that we perceive when we view the steam clouds. If the clouds appear white, it is because the droplets that are scattering the sunlight have a diameter roughly equal to (or greater than) the wavelength of visible light. The wavelength of light varies between about 400 nm (violet) to 700 nm (red) which means that these water droplets have to be at least 700 nm across. To put this in perspective, the smallest particles of coffee in an espresso grind are about 10 μm diameter which is 14 x bigger than the droplets in the steam cloud.

Of course, how water droplets scatter light above a steaming coffee has implications for our understanding of why the clouds in the sky appear white (and why the sky is blue). Someone who did a lot of early work in understanding the way that light scattered off water droplets in air was John Tyndall (1820-1893). Tyndall was an experimentalist as well as a famous communicator of science. He regularly gave lectures at the Royal Institution that included demonstrations of the experiments that he himself was working on¹. One of these involved scattering light from water droplets (and therefore demonstrating why he thought the sky was blue).

Interior of Cable co
Light streaming into the cafe.

The idea is that sunlight scatters from water droplets differently depending on the diameter of the droplet. When the water droplets are approximately the diameter of the wavelength of red light, 700 nm, there is very little wavelength dependence to the light scattering. Practically this means that the droplets will appear white. If on the other hand, the droplets are much smaller than the wavelength of light, the light scattering starts to be wavelength dependent. So as the droplet gets smaller, blue light (short wavelength) gets scattered a lot by the droplets, while red light (long wavelength) is not scattered so much. This means that if you are looking at a cloud of steam formed by these small droplets at an angle between the sunlight and yourself (say, 90º), the cloud will appear to have a blue tinge. If on the other hand you look straight through the cloud at the sunlight coming in, it will have a red-hue because the blue light will have been scattered out of the cloud leaving only the red colours to come through.

The experiment can be easily demonstrated at home by using very dilute milk in water (see video here or further explanation here). If you put a few drops of milk in a glass of water and then look at the colour of the milky-water as a function of angle, you should see it change from red to blue as you move the glass relative to the light source. The connection with the blue sky seems clear, small particles (in-fact, they can be as small as molecules) scatter blue light preferentially and so, apart from at sunrise and sunset, the sky will appear blue. As Tyndall wrote:

“This experiment is representative, and it illustrates a general principle…. that particles of infinitesimal size, without any colour of their own, and irrespective of the optical properties exhibited by the substances in a massive state, are competent to produce the colour of the sky.”²

Cable Co is at 4 Bridge House, Chamberlayne Road, NW10 3NR

¹A Vision of Modern Science, John Tyndall and the role of the scientist in Victorian culture, U. DeYoung, Palgrage MacMillan, 2011

²Quoted in John Tyndall, Essays on a Natural Philosopher, Ed. WH. Brock, ND. McMillan, RC. Mollan, Royal Dublin Society, 1981

 

http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html

 

Categories
Coffee cup science General Home experiments Observations Science history Tea

Is sixty the old forty?

Lundenwic coffee
What is the ideal temperature at which to serve coffee?

What is the optimum temperature at which to enjoy a cup of coffee?

A brief check online for the “ideal” serving temperature for coffee suggested a temperature of around 49-60ºC (120-140ºF, 313-333K) for flavour or 70-80ºC (158-176ºF, 343.1-353.1K) for a hot drink. In my own experiments (purely to write this article you understand), I found that I most enjoyed a lovely coffee from The Roasting House (prepared by V60) at around 52ºC. My old chemistry teacher must have been one who enjoyed the flavour of his coffee too. His advice for A-level practicals was that if we wanted to know what 60ºC ‘felt’ like, we should consider that it feels the same on the back of our hand as the underside of our cup of coffee. So, for argument’s sake, let’s say that we serve our coffee at the upper end of the flavour appreciation scale: 60ºC.

But, have you ever stopped to consider what 60ºC means or even, how we arrived at this particular temperature scale? Why do we measure temperature in the way that we do? While there are interesting stories behind the Fahrenheit scale, today’s post concerns the Celsius, or Centigrade, scale. Indeed, we use “degree Celsius” and “degree Centigrade” almost interchangeably to mean that temperature scale that has 0ºC as the melting point, and 100ºC as the boiling point, of water. It is one of those things that has become so habitual that setting 0ºC at the freezing end and 100ºC at the boiling end seems obvious, intuitive, natural.

thermometer in a nun mug
Careful how you drink your coffee if you repeat this experiment!

And yet the temperature scale that Anders Celsius (1701-1744) invented back in 1741 did not, initially, work this way at all¹. Celsius’s scale did indeed count from 0ºC to 100ºC and was defined using the same fixed points we use now. But rather than counting up from the melting point, Celsius’s scale counted up from 0ºC at the boiling point to 100ºC at the freezing point. Rather than degrees of warmth, Celsius’s scale counted degrees of cold. So, in the original Celsius scale, the serving temperature of coffee should be 40ºC: Sixty is indeed the old forty*.

Which immediately begs a question. Why is it that we count temperature up (the numbers get higher as it gets hotter)? A first answer could be that we view that temperature is a form of measurement of ‘heat’ and that heat is an energy. Consequently, something cold has less energy than something hot, “cold” is the absence of “heat” and therefore what we should measure is “heat”. This means that our thermometers need to indicate higher numbers as the temperature gets hotter, and so we are now counting the correct way. While this is good as far as it goes and certainly is our current understanding of ‘heat’, ‘cold’ and temperature, how is it that we have come to think of heat as energy and cold as the absence of heat? It was certainly not clear to scientists in the Renaissance period. Francis Bacon (1561-1626) considered that cold was a form of “contractive motion” while Pierre Gassendi (1592-1655) thought that although ‘caloric’ atoms were needed to explain heat, ‘frigoric’ atoms were also needed to explain cold.

effect of motivation on experience of pleasure while drinking coffee
How heat, rather than visible light, is reflected provides clues as to why we measure temperature ‘up’.

One experiment that helped to show that heat was an energy (and so lent support to the idea of measuring temperature ‘up’) was that of the reflection of heat by mirrors. In the experiment, two concave mirrors are placed facing each other, some distance apart. Each mirror has a focal length of, say, 15 cm. A hot object is placed at the focal length of the first mirror. At the focal point of the second mirror, is placed a thermometer. As soon as both objects are in place, the temperature indicated by the thermometer increases. If the mirror were covered or the thermometer moved away from the focal point, the temperature indicated decreases again to that of the room. It is an experiment which can easily be demonstrated in a lecture hall and which fitted with a view point that cold is the absence of heat.

However, around the same time as this initial demonstration, Marc-Auguste Pictet did another experiment, the (apparent) reflection of cold². The experiment was as before but in Pictet’s second experiment, a flask containing ice replaced the hot object. On repeating the experiment the temperature indicated by the thermometer decreased. Covering the mirror or moving the thermometer from the focal point of the mirror resulted in the indicated temperature increasing again. Just as ‘heat’ was reflected in the mirrors, so too (seemingly) was ‘cold’.

So, the question is, how do you know what you believe you know about heat? Are there experiments that you can design that could help to disprove a theory of ‘frigoric’? And how do you explain the experiments of Pictet? Reader, it’s over to you.

 

*Within ten years of Celsius’s death (of tuberculosis in 1744), his colleagues Martin Strömer and Daniel Ekström had inverted Celsius’s original temperature scale to the form we know today. A similar scale designed by Jean Pierre Christin was also in use by 1743³.

¹”Evolution of the Thermometer 1592-1743″, Henry Carrington Bolton, The Chemical Publishing Company, 1900

²”Inventing Temperature”, Hasok Chang, Oxford University Press, 2008

³”The science of measurement, a historical survey”, Herbert Arthur Klein, Dover Publications Inc. 1988

 

Categories
Coffee cup science General Home experiments Observations Tea

Making a splash

You spilled your coffee, a terrible accident or an opportunity to start noticing?

Why do some droplets splash  while others stay, well, drop like? It turns out that there is some surprising physics at play here. When a drop of water, or coffee, falls from a height and onto a flat surface (such as glass), we are accustomed to seeing the droplet fracture into a type of crown of smaller droplets that form a mess over the surface. Visually spectacular, these splashing droplets have even been made into an art form (here).

Fast frame-rate photography reveals how each micro-droplet breaks away from the splashing drop:

Video taken from Vimeo – “Drop impact on a solid surface”, a review by Josserand and Thoroddsen.

 

So it perhaps surprising to discover that there are many things about this process that we do not yet understand. Firstly, if you reduce the gas pressure that surrounds the drop as it falls, it does not make a splash. In the extreme, this means that if you were to spill your coffee in a vacuum, you would not see the crown-like splashing behaviour that we have come to expect of falling liquids. Rather than splash, a droplet falling in low pressure spreads out on impact as a flattening droplet. This counterintuitive result was first described in a 2005 study (here) that compared the effect on splashing of droplets with different viscosities (methanol, ethanol, 2-propanol) falling through different gasses.

cortado, Brunswick House, everyday physics, coffee cup science
Don’t spill it!
But would a latte splash more or less than a long black?

The authors of the study ruled out the effect of air entrapment surrounding the droplet as it falls as high speed photography had not indicated any air bubbles in the droplet just before impact. Instead they considered that whether a drop splashes on impact – or not – depended on the balance between the surface tension of the falling liquid and the stress on the drop created by the restraining pressure of the surrounding gas. Calculating these stresses led to a second surprising result. Whether a drop splashes on impact or not depends on its viscosity (as well as the gas pressure and the speed of impact). But the surprising bit is that the more viscous the liquid, the greater the splash.

From a common-sense perspective (that may or may not have any bearing on the reality of the situation), an extremely viscous liquid like honey should not splash as much as a less viscous liquid like coffee. This suggests that there is an upper-limit in viscosity to the relation predicted in the 2005 study. After all, although the authors did change the viscosity of the liquids, the range of viscosity they studied was not as great as the difference between coffee and honey. This sounds like a perfect experiment for some kitchen-top science and so if any reader can share the results of their experiments on the relative splashes formed by coffee and honey, I would love to hear of them.

 

Categories
General Home experiments Observations Science history slow Tea

Reflections on physics and coffee

BeanThinking started as a way of slowing down and appreciating connections, often between a coffee and the physics of the wider world but also in terms of what can be noticed in any café. Perhaps, for this first post of 2017, it’s worth spending five minutes looking at your coffee while you drink it to see what you notice. Here are a few coffee connections that occurred to me recently:

reflections, surface tension
Reflections on a coffee.

Parallel lines and surface reflection: The parallel lines on the ceiling of a café were reflected in a long black. Surface tension effects on the coffee meant that the reflections were curved and not at all parallel. A piece of dust on the surface of the coffee was revealed in the reflection by the curved reflections of the ceiling. Astronomers can use similar effects (where images of a star appear in a different location to that expected) to infer the presence of dark objects between distant stars and their telescope. This gravitational lensing can be used to detect quasars or clusters of galaxies.

 

 

 

layering of coffee long black
Layers of coffee

Layering of crema as the coffee is consumed: The coffee stain effect and this layering of the crema suggests a connection between a coffee cup and geology. It used to be my habit to take a mug of tea with me when I taught small groups of undergraduates. In the course of one of these tutorials, a student (who had been observing similar layering in my tea mug) said, “You drink your tea faster when it is cooler than when it is hot”. Full marks for observation, but not sure what it said about his attention during my tutorials! Similar observations though can help geologists estimate the age of different fossils.

 

interference patterns on coffee
Bubbles in coffee

Bubble reflections: An old one but the interference patterns caused by bubbles on the surface of the coffee are full of fascinating physics. The fact that the bubbles are at the side of the cup and seem to be grouped into clusters of bubbles may also be connected with surface tension effects (although there is a piece of weather lore that connects the position of the bubbles to the weather. If anyone ever does any experiments to investigate this particular lore, I’d love to hear about them).

 

 

Coffee, Van Gogh
Art in a coffee cup

Van Gogh’s Starry Night: The effects of vortices and turbulence caused the crema of a black coffee to swirl into patterns reminiscent of this famous painting by Van Gogh. As a result of posting this image on Twitter, @imthursty sent me a link to this preprint of a paper submitted to the arxiv: the connections between Van Gogh’s work and turbulence. A great piece of coffee combining with art and science.

 

So many connections can be made between tea, coffee and science and the wider world, I’d love to see the connections that other people make. So, if you see some interesting physics, science or connections in your coffee cup, why not email me, or contact me via FB or Twitter.

 

Categories
General Home experiments Observations Tea

An easy way to get a halo

The other day I was talking to a primary school child about condensation, what it was, where to see it etc. So I asked,

“Do you drink coffee?”

“No.”

“Do you drink tea?”

“No”

(I started to worry about the future generations). Nonetheless, I pulled out my cup of steaming coffee and pointed to the water droplets around the edge of the mug (which are very common if you haven’t warmed your cup before pouring your hot coffee into it) and noticed a sudden expression of recognition cross the child’s face.

“Like when you breathe on a mirror?”

Kettle drum at Amoret
Condensation on around the top of the jug on this V60

Yes, exactly so (and probably a much better example for a kid anyway, the problem of being an adult with a one track mind!). As the child had realised, the science in your coffee cup is connected to phenomena that occur elsewhere in the world. In the case of condensation, it occurs when the temperature of the surface onto which condensation happens is below what is called the “dew point”. Determined by the relative humidity in the environment, the dew point is the temperature below which water vapour in the air will condense into liquid water.

Of course the dew point gets its name from the dew that can form after a chilly night. Which brings us to another property of those water droplets that form around the rim of your coffee mug. Although it is not easy to see on the mug, each droplet is acting as a lens, focussing the light that falls onto it. As the surface of the mug is fairly flat, rather than form spherical droplets, the drops that form on the side of the mug are squashed hemispheres. This is not the case when dew forms on grass. Tiny hairs on the surface of the grass protrude from the leaf meaning that the water droplets form into spheres (which is, incidentally very similar to the reason that a duck is so waterproof). When the sun comes up, each sphere of water focusses the sunlight onto the grass behind it which reflects it back, right in the direction it came from.

heiligenschein, self portrait
Self-portrait with weak heiligenschein. Share your photos with me on FB or Twitter.

This means that if you stand with your back to the sun and look at your shadow on dew covered grass, you will very probably see a region of bright light surrounding your head, your heiligenschein. German for “Holy light”, heiligenschein is the effect of all of those spherical dew lenses reflecting the sunlight back towards you. You can only see the effect around your ‘anti-solar’ point (a position defined as being 180º from the Sun from the viewpoint of the observer, see here for what this means visually). This means that while you will see heilgenschein around your head, or around the shadow of the camera that you use to photograph it, you will never see the halo around someone else’s head even while they themselves can clearly see it.

I’m sure there’s some sort of metaphor there, perhaps one to contemplate next time you’re drinking a hot, steaming coffee.

 

Categories
Coffee cup science Observations Tea

Coffee: The mathematical and the beautiful

Last week, a new study was published that explored the mathematics behind brewing the perfect filter coffee.  The research, summarised here, modelled the brewing process as being composed of a quick, surface extraction from the coffee grounds, coupled with a slower brew, where the water was able to get into the interior of the coffee grind. It was an interesting study and the authors are now looking at grind shape and the effect of how you wet the grounds. However, what struck me was that the authors mentioned scanning electron microscopy (SEM) images of ground coffee. A lovely idea, what does coffee look like when magnified hundreds (or thousands) of times?

So here are a few images that I found shared under Creative Commons Licenses. I hope you find them as fascinating as I do.

1) A green coffee bean:

Green coffee bean under the microscope
A green coffee bean. Sadly no details as to magnification. Image shared under CC license from Nestle, Flickr

2) Instant Coffee

Instant coffee from Nestle
Spray dried instant coffee from the Nestle, Flickr account. Image shared under CC license.

3) Roast and ground coffee (fluorescence microscopy image)

ground coffee, fluorescence image
Ever wondered what your coffee looked like when magnified many times? This image using fluorescence microscopy is of roasted coffee. Note the similarities between this image and the following one (which has a scale bar).  Image shared under CC license from Nestle, Flickr

3b) More ground, roasted coffee, this time from Zeiss

Zeiss roast coffee
Scanning electron microscope image of roast (and ground) coffee magnified 750x. Image from Zeiss, Flickr, Todd Simpson, UWO Nanofabrication Facility. Shared under CC license. (To put the scale bar in perspective, it is the size of the smallest particles in an espresso grind. Clearly, the grind here is quite coarse).

4) Finally, an image of tea, just to keep this article tea-coffee balanced:

Green tea under the microscope
Green tea as seen under the microscope by the scientists at Nestle. Shared under CC license Nestle, Flickr.

If you come across any great images of coffee (or tea) under the microscope, please do share them. In the meanwhile, enjoy your coffee however you brew it.

Categories
Coffee cup science Coffee review General Observations Sustainability/environmental Tea

A cup of tea for a light bulb moment at Ginger and White, Hampstead

Coffee, Ginger and White, Hampstead
Coffee at Ginger and White, Hampstead

It was late afternoon by the time we stopped by Ginger and White in Hampstead. The warm weather meant that we could enjoy time spent sitting outdoors in the little alleyway in front of the café. We had been taking a friend around the various sights (and foodie places) of London and so stopped here before heading back home. The long black, cortado and soya latte were all very well done and, while the others had enjoyed a crepe at La Creperie de Hampstead just around the corner, I took the opportunity to try the excellent banana bread on offer at Ginger and White. There was a fairly good selection of cakes on offer, but sadly those that the staff could confidently affirm were nut free were far fewer. However, the moist and tasty banana bread was a good option anyway. Coffee was roasted by Square Mile and there were also Square Mile beans available for purchase should you wish to take some home with you. While the café was fairly busy, it was nevertheless a relaxing place to sit and watch the people of Hampstead go by.

The interior of Ginger and Whites
Everything is connected. From the lights to your cup of tea.

As I was looking around, wondering what the physics part of this cafe-physics review would be, I had what you could call a “light-bulb moment”. The walls of the building opposite were reflected in the windows of the café but looking inside, I noticed the lights which appeared to be LED lightbulbs set-back into the ceiling. Along with requiring less energy to power than conventional or halogen lightbulbs, LED lightbulbs in a café offer another, more poetic advantage for the café: they have a connection to the drinks being served and particularly tea. It’s all about diffusion.

At the heart of an LED light, there are two materials that form a junction. On one side of the junction is a semiconductor material that conducts electricity by means of electrons. Electrons conduct electricity in metals and are the ‘normal’ way that we consider electrical current to  be carried. On the other side of the junction is a different semiconductor, one that still conducts electricity but this time does so with carriers called ‘holes’. You can view the electrons as having a negative charge and the holes as having a positive charge.

tea bag, tea cup, diffusion, turbulence
What happens when you put a tea bag into a cup of cold water. How long until the water becomes ‘tea’?

But what happens at the junction? Is there really a sharp barrier between these two types of material? Think about putting a tea bag in a cup of cold water, does the tea bag just sit there or does it slowly, very slowly, start to diffuse tea into the cold water? It is a similar thing for the two materials. Slowly the electrons diffuse into the hole material and the holes into the electron material. In fact, mathematically, the same equations describe the process in the junction as in the tea cup. But unlike tea, in the LED, the holes and electrons have an electric charge associated with them and so, as they diffuse away from the junction, they set up an electric field across the junction. It is this electric field that eventually stops any further diffusion of electrons or holes across the junction and sets up the conditions necessary for LEDs to emit light. It would be like having a tea bag that diffuses tea into the cup until it is perfectly brewed and no further.

Of course, there is much more than this to understanding LEDs. If you’re interested, there is further information here. I find it fascinating however that what happens in your tea cup, is also happening on many different scales in many places in the universe. And of course, in the lighting of cafés and coffee houses around the world.

Ginger and Whites is at 4a-5a Perrins Court, NW3 1QS

 

Categories
General Observations slow Sustainability/environmental Tea

Environmentalism through V60s

Is there a parallel between trying to live more sustainably and the art, or science, of coffee appreciation?

San Sebastian via Aeropress
Enjoying a coffee prepared in an Aeropress at Alchemy

Consider the way that we experience our coffees. Who would not wish that more people took time to enjoy great coffees, perhaps single-origin pour-overs, precisely measured and lovingly made, obviously without milk. But we know from experience that not everyone is ready to take the risk of trying a new café and paying that bit extra for a coffee they do not know. Our own coffee journey may illustrate this point. My student days were filled with supermarket (cheapest brand) instant and machine coffee (20p between lectures). Slowly I graduated (quite literally, a well known chain opened close to the university in my final year) to grande lattes, flavoured with nutmeg and similar drinks. A smaller chain introduced me to macchiatos and black coffees before I found a start-up roasting company on the internet and suddenly my mornings were transformed with the fragrance of freshly roasted and freshly ground, aromatic and lovely coffee.

Each step I took introduced me to better, more interesting coffees. New coffee roasters opened offering different levels of roast and different types of bean. Great independent cafés started up which featured coffees brewed in new and innovative ways (the Aeropress was only invented in 2005). Social media and more traditional friend circles introduced me to people who really take time to savour their coffee and which in turn has enabled me to grow in my own coffee appreciation. Would I have jumped from instant to pour-over? Probably not. And yet, I know that I am still on a coffee-appreciation journey: There is still so much more to learn, so many new things to experience, it is a journey I’m very happy to have embarked upon.

kettle, V60, spout, pourover, v60 preparation
How much CO2 does over-filling your kettle really produce?

So what is the link with environmentalism or indeed science? Well, how many times have you heard that if only we filled the kettle just to the correct amount, we would save so many tonnes of carbon dioxide emissions annually? A counter argument points out that given how much pollution we are actually responsible for, merely correctly filling the kettle (or avoiding takeaway cups) is going to have negligible environmental benefit. It is here that I think that the analogy comes in.

It is true that, when you tot up your daily energy consumption, the use of a kettle is not a very big part of it*. For me, even when I overestimated my kettle use (and underestimated the energy costs involved in transporting the kettle/coffee etc. to my kitchen as this became difficult to estimate), my energy use coming from the kettle was only 2% of my daily average. If I only considered the energy consumption due to electricity per day, of course the contribution of the kettle would be higher but it is still not that big a deal.

Over-boiling the kettle does not seem to make that much of a difference when compared to the difference we will have to make in order to limit climate change. Which takes us to the very valid argument that “if everyone does a little, we’ll achieve only a little”†. But, is it worth being just a little bit more optimistic on this? Let’s bring in the coffee.

Earth from space, South America, coffee
One planet. One home.
The Blue Marble, Credit, NASA: Image created by Reto Stockli with the help of Alan Nelson, under the leadership of Fritz Hasler

It is all too easy to breeze through life not considering our environmental actions, I’d argue that this is the instant coffee stage. As we start to become more aware of the environment, we perform small actions (buying – and of course reusing – a keepcup, only filling the kettle just-so). That’s great, we’re drinking pumpkin-spice lattes. It may not be the best coffee we can get but we are enjoying it. Analogously, as we increase our environmental awareness (and subsequent responsibility) we seem to find that small things become more enjoyable, and even more rewarding. The effort involved in trying to improve our environmental behaviour brings benefits in terms of the amount we enjoy or the appreciation of the things that we have. The small step brought about by considering our kettle use, enables us to make the larger steps that are necessary to behave more environmentally. Trying to make big changes quickly may, in some ways be great (it would indeed be better if everyone appreciated single-origin pour-overs without milk), but it is unlikely to work. To my mind, even if people really started to appreciate good pumpkin-spice lattes that would be a step away from the horrors of instant and towards a better future!

But is an environmental pumpkin spice latte enough? Can I say that I now behave in a properly sustainable and environmental way? Sadly not. Exactly as with the coffee, I am far too aware that I’m on a sustainability journey: There is still so much more to learn, so many new things to experience, it is a journey I’m very happy to have embarked upon. Some do a lot better with the environmentalism, some are still drinking instant coffee, but small steps help us to make the large steps that are going to be needed. Back in the 1990s, as more people began drinking flavoured, grande lattes, so it became possible for the small independent cafes to open up and improve the coffees on offer. We need to move on from pumpkin spice environmentalism, let’s hope we make the steps soon enough.

*You can easily calculate your own energy use with the guidance in David MacKay’s excellent book “Sustainable Energy – without the hot air” that he made fully available online (click the link). In a series of easy steps and estimates that you can make, he helps you to calculate your average daily energy consumption (which can be translated, if you so wished, to a personal carbon dioxide emissions calculation). I would highly recommend going through and looking at your own consumption to see how big an effect, for you personally, over-filling the kettle is.

† Quote from “Sustainable Energy – without the hot air” by David MacKay, UIT Cambridge Ltd, 2009