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.
Water heating
Jar handling*
Cup preparation
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).
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.
It’s nearly 7 years since Kaffeine first opened its doors on Great Titchfield St, but Kaffeine on Eastcastle Street is a new addition having opened just over a year ago. We visited the younger Kaffeine a couple of weekends ago when looking for a coffee in the Oxford St area. Along with an iced coffee, an Americano and a long black, we had a raspberry/cashew slice and a slice of banana bread. It was a relief to find that Kaffeine had a good nut policy so I could confidently enjoy my banana bread, knowing it was nut-free, while a friend devoured the cashew containing slice. The staff were attentive and friendly and there was plenty of space inside to sit and chat while taking in the surroundings. In this regard, it was nice to see this same point being made on Kaffeine’s own website where it says that you can “…sit at the high stools at the massive sun filled front windows and watch the world go by”. With the accompanying coffee, what more could you want? The coffee was, of course, very good (beans from Square Mile), and it was great to see that part of the philosophy behind Kaffeine is to take “the art and science and practice of making espresso coffee to a whole new level”. It’s always a pleasure to see those three distinct, but essential, elements combined. I do however remain unconvinced that many could tell the difference (in a blind taste test) between an Americano and a long black.
The table top at Kaffeine, Eastcastle St.
Complimentary mint-infused water was on offer at the back of the cafe and, although this made the Daily Grindlast week, there was just too much to notice at Kaffeine to make this the subject of the cafe-physics review. Indeed, from the perspective of anyone who wants to slow down and notice things in a café, Kaffeine is brilliant. This cafe-physics review could have been about so many different things. There were the weights holding the door open in a pulley system. The trademark neon sign. The compact-ness of the cashew/raspberry slice or the reflectivity of the copper on the side of the counter. I was in cafe-physics review heaven! So many different mental alleyways to run down and explore as the different bits of physics came into view. From pulleys to Archimedes, cakes to ceramics science, copper to atoms or to the odd puzzle about the colour of gold, all these will have to wait for another time. This time, what struck me was not what could be seen but what could be felt.
Far from going into a subjective piece about the ambience of the cafe, I mean this statement far more literally. The table, with the wooden grain, felt rough. In the middle of the table, a piece of slate had a surface that was more smooth and then, on the walls behind us, highly glazed tiles were very smooth indeed. What do we mean by rough or smooth, how rough is rough, how smooth is smooth and what has it to do with the “magic mirrors” of Japan?
Smooth tiled wall at Kaffeine
The wooden bit of the table for instance has a surface that undulates with a height of the order of about a millimetre. The slate is far smoother but the surface would still be rough, probably on a length scale tens to hundred microns or so (about the size of espresso to medium grind coffee). The tiles are a lot smoother than both the wood or the slate but they are still not so smooth that they could be considered flat on an atomic scale. To be flat on an atomic scale, the surface would have to have a height variation 100 000 times smaller than the smallest particles in an espresso grind*. While some crystals can, naturally, have ‘faces’ that are this smooth, the semiconductor industry needs to be able to achieve this level of flatness routinely to provide the electronics for your smart phones, computers and even perhaps the electronic scales that are used to help you make your coffee.
The mirror-like copper clad counter.
In ordinary life however, perhaps we think that a smooth surface is like that of a mirror. So it is worth taking a look at an odd type of mirror for which very small variations on the surface cause a very strange effect: the “Magic mirrors” of the far East. Typically made of bronze, these mirrors have been manufactured for nearly 2000 years. On the back surface of the mirror is an artwork (perhaps signs of the zodiac or other religious symbols) which is in relief. The front of the mirror meanwhile is highly polished but slightly convex. Looking directly at the front surface of the mirror, there is no visible sign of the image on the back. Maybe you don’t find this surprising, the mirror is solid bronze after all and we can’t see through solid metal. However, if you were to take a step back, shine light on the front of the mirror and look at the reflection of the mirror projected onto the wall, the image at the back can clearly be seen, there in the reflection (you can see photos of this effect here).
Initially this phenomenon was dismissed as ‘trickery’ but subsequent, careful, study showed that small deviations from perfect curvature on the reflecting surface were enough to cause the effect. Although the mirrors were cast and then polished, nonetheless, stresses and strains from the pattern on the back had propagated through the atomic structure that forms the metal and resulted in tiny, invisible to the eye, changes on the front surface of the mirror. Sometimes it does appear that looking at things in a different light can really change our impression of what something is.
Kaffeine can be found at 15 Eastcastle St. W1T 3AY
* Scaling to coffee grind size approximate but based on measurement of grind size reported here.
Mint in a glass of water. Do other species appreciate a mint aroma too?
Very often, in a café, there will be a jug of mint infused water sitting in a corner, offered as a complimentary accompaniment to the coffee. A fragrant way of ‘refreshing our palate’. Mint is one of many aromatic plants that we use to scent our rooms or freshen our breath. But are we the only species that uses mint and similar aromatics such as lavender in this way? Do other animals appreciate the aroma that a freshly plucked mint leaf can provide?
A few weeks ago (in mid-spring in the northern hemisphere), I noticed some odd bird behaviour going on just outside the window. A blue tit (Cyanistes caeruleus) had landed on the edge of a pot of mint and was busy tearing leaves off the plant that was growing just outside. We watched as the bird hopped around to the other side of the pot, tearing off the younger, fresher leaves. What on earth was it up to?
A sprig of mint growing in a pot.
A quick use of duckduckgo (or google if you’d prefer), revealed a surprising answer (or at least further questions) to this odd behaviour. It would appear that blue tits have been observed to pick mint, lavender and curry plant leaves and use them to line their nest. Moreover, individual blue tits have a preference for different plants. Some females (it appears to be the female that collects the leaves) prefer mint, some lavender, and presumably some prefer curry. There is even a video from “Springwatch” that filmed this behaviour in a blue tit nest a few years ago (link is here). Similar behaviour has been observed in some other bird species such as the Starling (Sturnus vulgaris) but not in other, related bird species such as coal tits or great tits. So what could be driving this behaviour, is it, as the BBC said in its headline “aromatherapy”?
According to research, in fragranced nests, the number of bacteria/pathogens on the chicks was significantly reduced compared with non-scented nests. The chicks also seemed healthier, not only did they have a higher red blood cell count, they grew faster. What remains unclear is the reason that this should be so. Is it that the mint is anti-bacterial? Or is it, as suggested in the programme Springwatch, that the smell can perhaps relax the immune system of the birds allowing them to “put more effort into their growth”. Moreover, how did the birds first know how to pick these plants? How did this behaviour spread?
There is always a risk that we anthropomorphise other animals and consider that they appreciate aromatherapy when they are not doing so. There is however an alternative risk that we reduce animals almost to biological automata that manifest different behaviours purely for the biological advantage it gives them (as if they know that in advance). These questions are too far outside my ‘specialist’ area, for me to attempt to consider on Bean Thinking. However, as an ‘interested observer’ I can still appreciate and wonder at the interesting sights that five minutes spent observing our surroundings can provide. I will also enjoy the feeling it brings to know that we are sharing the mint on the window sill with the blue tits and their chicks.
Have you ever observed similar behaviour by birds in your neighbourhood? What birds around the world share our preference for mint? Comments are always welcome either here or on Facebook or Twitter.
Hidden somewhere deep in “The Lanes” in Brighton is a great little café that goes by the (somewhat appropriate) name “The Lanes Coffee House“. The Lanes is a set of old, narrow streets that form quite a maze, a great place to explore if you are a visitor to Brighton. There are two entrances to The Lanes Coffee House, which is fortunate as we may not have found the ‘front’ entrance while wandering aimlessly around a few weeks ago. With plenty of seats inside, and a few at the back, The Lanes Coffee House has a lot to notice if you like to sit in a café, enjoying your coffee, without the distractions of your phone or laptop. Pictures by a local artist decorate the walls, with each picture featuring a Brighton scene and The Lanes Coffee House in a “Where’s Wally” type format. A window opens up to the narrow lane outside and there is also plenty to notice inside the café where we enjoyed an Americano and Soya hot chocolate. Sadly on the day that we tried The Lanes there weren’t any nut-free cakes at the counter and so, as compensation, we had to have a bag of fudge.
We sat at a table on which there was a tiny metal bucket that was used for holding sugar (see picture). With Brighton being a sea-side town, this immediately conjured up images of sandcastles and picnic sandwiches. The only problem with this image of course is the fact that Brighton has a pebble beach rather than a sandy one. So rather than think about sandcastles I got thinking about something slightly different: If you were to partially fill a bucket with some sand, put a stone from the beach in the bucket and then fill the rest of the bucket with sand, how could you easily retrieve that stone without fishing around in the sand for it?
Bucket with sugar at The Lanes
This question came up, in a slightly different way, in a paper published nearly 30 years ago called “Why the Brazil nuts are on top“. That paper dealt with the question of why, in a package of mixed nuts, the Brazil nuts (i.e. the largest nuts) were frequently found to be on top when the package was opened. Termed, the “Brazil nut effect”, it turns out that this question is not just an odd bit of physics but has relevance to the packaging industry and earthquake dynamics. If you were to shake the bucket of sand containing that one pebble, the stone would rise up through the sand, eventually coming to the surface. The question is, what is driving this ‘anti-gravity’ type behaviour? Why do the heavy objects rise to the top?
Obviously, being a coffee website, to do the experiment with sand and a stone is a bit, well, dull. So, using dried, used, grounds (well, what do you do with your used coffee grounds?) and a green coffee bean*, I repeated the experiment on a smaller scale, in a shot glass. I put the green bean at the bottom of the shot glass and then covered it with coffee grounds (up to half way up the shot glass). To prevent too much mess, I covered the shot-glass with a piece of clingfilm. In order to avoid too much vertical shaking, the glass was hit repeatedly from the side in order to ‘shake’ it. It took 40 seconds of vigorous shaking but the green bean eventually started to poke above the surface. The heavy large bean had moved up through the glass upon being shaken, just as the Brazil nuts end up on top in a bag of mixed nuts. Just how had that happened?
Now you see it, after shaking the green bean rises to the surface
It turns out that there are several things going on. Firstly, as the 1987 paper discussed, the small grains of sand (or ground coffee) can fall into voids under the large Brazil nut/stone/coffee bean. This has the effect of pushing the nut/stone/coffee bean upwards until it reaches the surface. The coffee bean could move down through the grounds but this would require the collective movement of a large number of coffee grounds under the bean to form a void large enough for the bean to fall into, something that is fairly unlikely. So the coffee bean will move up, the coffee grounds will move down. Then there is an effect that is more familiar to coffee drinkers, convection. The idea here is that although all the particles in the glass (or bucket) can move upwards as the container is shaken, only the small particles can move down again through the small voids created at the sides of the container. Rather like the movement of milk in a hot coffee, this again has the effect that the small particles push the larger particle up.
After this though things start to get more complicated. Along with what has been termed “the inverse Brazil nut effect”, it seems that air pressure may play a role in the Brazil nut effect. Who knew that Brazil nuts could be so complicated! Perhaps though, to finish our train of thought on The Lanes we could turn this effect into a non-physics, almost allegorical, meditation? If we, as a society, are collectively shaken enough, can small, individual actions do what at first seems impossible? I wouldn’t want to push the analogy too far, but it does seem an interesting problem on which to dwell for a further five minutes while you are sipping on your long black (or, as this is officially the first day of summer, your cold brew).
(If you’d rather think about the physics of sandcastles, you can find out more about them here).
*The green coffee bean came from a jute coffee sack that had been given to me by Amoret coffee for my composting worms. Thanks Amoret!
The Lanes Coffee House is at 59D Ship Street Brighton, BN1 1AE
In the UK Science Museum’s library there is a book, written in 1910, by Jean Perrin called “Brownian Movement and Molecular reality”. To some extent, there is nothing surprising about the book. It describes a phenomenon that occurs in your coffee cup and the author’s own attempts to understand it. Nonetheless, this little book is quite remarkable. It is perhaps hard, from our perspective in 2016, to imagine that at the time of Perrin’s work, the idea of the existence of molecules in water was still controversial. It was even debated whether it was legitimate to hypothesise the existence of molecules (which were, almost by definition, un-detectable). However, none of that is really relevant to the question confronting today’s Daily Grind. Today, the question is how can this book help us to find beauty in a coffee cup?
What does a one hundred year old book have to do with finding beauty in a coffee cup? Perrin received the Nobel Prize in 1926 for his work establishing the molecular origins of Brownian motion and, associated with it, his determination of the value of Avogadro’s constant. It is perhaps why he wrote the book. (The experiment that he used to do this is described in a previous Daily Grind article that can be found here.) It is in his description though, both of the theory and the experiments involving Brownian motion that this little book is relevant for today. One word repeatedly crops up in Perrin’s description of Brownian motion. It comes up when he describes the theory. It comes up when he describes other people’s experiments. It comes up when he describes bits of the maths of the theory. The word? Beautiful*.
Michael Polanyi, by Elliott & Fry, vintage print, (1930s), Thanks to National Portrait Gallery for use of this image.
Throughout history, many scientists have recognised, and worked for, the beauty that they see in the science around them. In a 2007 TED talk, Murray Gell-Mann said
“What is striking and remarkable is in fundamental physics a beautiful or elegant theory is more likely to be right than a theory that is inelegant.”
So it is interesting that, although we may agree that scientific theories can be “beautiful” or “elegant”, we do not seem to have a way of quantifying what precisely beauty is. It is similar for those things that are beautiful that we find in every day life. The beauty of a sunset, or the way the light catches the ripples on the surface of a lake, these are things that we recognise as beautiful without being able to articulate what it is about them that makes them so. Instead we recognise beauty as something that strikes us when we encounter it. Elaine Scarry has talked about this as a “de-centering” that we experience when we come across beauty. Scarry writes that, when we encounter the beautiful:
“It is not that we cease to stand at the center of the world, for we never stood there. It is that we cease to stand even at the center of our own world”.¹
It is therefore quite concerning that she goes on to suggest that conversations about beauty (of paintings, poems etc) have been banished from study in the humanities “…we speak about their beauty only in whispers.”¹ This does not seem to have happened yet in science where it is still common to hear about a beautiful equation or an elegant experiment. But is there a creeping ‘ideological utilitarianism” in the scientific community? According to Michael Polanyi ²
“Ideological utilitarianism censures Archimedes today for speaking lightly of his own practical inventions and his passion for intellectual beauty, which he expressed by desiring his grave to be marked by his most beautiful geometrical theorem, is dismissed as an aberration.”²
While we may recoil from this sentiment, what do we write (or expect to read) in grant applications, scientific papers, popular science or even scientific outreach? How often is the utility of a piece of research emphasised rather than its elegance?
Does an appreciation of beauty help with a wider understanding of justice and environmental concerns? The Blue Marble, Credit, NASA: Image created by Reto Stockli with the help of Alan Nelson, under the leadership of Fritz Hasler
Another interesting question to ponder is whether our ability to appreciate (and discuss) beauty has wider ramifications. As many others have argued before her, Scarry suggests that the appreciation of the beauty in the world connects with our sense of justice¹. Recently the Pope too, in his great environmental encyclical, Laudato Si’ wrote³:
“If someone has not learned to stop and admire something beautiful, we should not be surprised if he or she treats everything as an object to be used and abused without scruple.”
Could it be true that part of the motivation that we need to change our ecological habits or stimulate our search for wider social justice is enhanced by our ability to slow down and appreciate the beautiful, wherever and whenever we find it?
So to return to our coffee. Is there something, anything, about our coffee or our tea that gives us such a radical de-centering experience? Can we, like Jean Perrin, appreciate the subtle beauty of the molecular interactions in our cup? Do we appreciate the moment as we prepare our brew? Or are we ideological utilitarians, seeing in our cup just another caffeine fix?
* Technically, the book in the Science Museum Library is a translation of Perrin’s work by Frederick Soddy. It is possible that it is Soddy’s translation rather than Perrin’s work itself that uses the word ‘beautiful’ repeatedly. It would be interesting to read Perrin’s book in its original French.
I would like to take this opportunity to say thank you to the Science Museum Library for being such a valuable resource and to the staff at the library for being so helpful.
“Brownian movement and molecular reality”, Jean Perrin, translated by F. Soddy, Taylor and Francis Publishers (1910)
1 Elaine Scarry, “On Beauty and Being Just”, Duckworth Publishers, 2006
2 Michael Polanyi, “Personal Knowledge, towards a post-critical philosophy” University of Chicago Press, 1958
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 Grindarticle (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.
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.
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!
How do you drink your cold-brew? How about iced-coffee or iced-tea? Would you drink it through a straw? Maybe a smoothie or a milkshake would be ok. Perhaps you’ve noticed that you need a large straw to drink that milkshake while a small straw works for ‘thinner’ drinks. But what is the connection between this and the measurement of your blood pressure? It is not that drinking coffee gives you high blood pressure or the reverse. That question can be left for discussion on other websites. No, the question is, can drinking a milkshake through a straw give you an insight into the problems of high blood pressure caused by the build up of cholesterol?
If you are currently in a café, why not try an experiment. Get two straws and try drinking a cold drink using both of them together. It’s tricky but it is do-able, you can drink your drink. Now place one straw such that it is ‘sucking’ on the air outside the glass with the other straw still in the drink. Without cheating you can no longer ‘suck’ up that cold brew. Plugging either end of the ‘free to air’ straw enables you once again to drink your coffee. This experiment demonstrates that you are not really ‘sucking’ the liquid through the straw, rather you are generating a pressure difference between the top of the straw (a lower pressure in your mouth) and atmospheric pressure (higher pressure, around the drink) that pushes the liquid through the straw. Attempting to drink through two straws when one is open to the atmosphere cancels out that pressure difference.
The straw on the left has a diameter of 3mm, on the right, 6mm.
Now another experiment. How do straws of different diameters affect the amount of liquid you can ‘pull’ through the straw? Try it. I have two straws in this picture, the smaller one has a diameter of 3mm, the larger one a diameter of 6mm. It takes a lot longer to drink a quantity of liquid through the smaller straw than it does the larger straw (assuming that you are drinking the same drink with each straw). For example, I drank 200ml of water in 10-12 sec with the larger straw but 26 sec with the smaller straw.
Back in the early nineteenth century two people were each investigating how liquid flowed through narrow tubes. Jean Leonard Marie Poiseuille (1797-1869) was investigating tubes of diameter 0.013-0.65mm in order to understand the flow of blood through capillaries in the body. Gotthilf Heinrich Ludwig Hagen (1797-1884) was investigating tubes between 2.3-6mm diameter (the same as the straws in the picture). Although they came to their conclusions independently, their work now forms the basis of parts of our understanding of the circulation of blood in the body†. What is now known as the Hagen-Poiseuille law states that the flow of liquid through the straw (or blood vessel) is proportional to the pressure difference between the two ends of the straw (how much you ‘suck’ so to speak) and the radius of the straw raised to the fourth power*. That is, it is the radius x radius x radius x radius. Doubling the radius of the straw results in a 2x2x2x2 (= 16) increase in flow rate.
Experimenting with the two straws does not give you quite the 16x difference that you may expect from this law perhaps partly because the flow into the straw is turbulent. If you maintained a uniform flow through the straws, you should find that the difference in flow rate between the two straws would be closer to 16x.
A straw in water, another physics-phenomenon that is worth contemplating for a while.
Of course, what applies to straws applies equally well to arteries or even the alveoli in your lungs. If your arteries get clogged by too much cholesterol, the reduction in the diameter of the artery leads to a reduced flow of the blood. A decrease in the diameter of an artery by just twenty percent more than halves the flow rate of blood through it (thereby increasing the blood pressure required to maintain ‘normal’ flow rate). Similarly the constriction of the alveoli in the lungs of asthmatics reduces the flow rate of air through the lungs in an asthma attack.
So it is not quite the fact that drinking cold-brew through a thin straw can give you high blood pressure. It is rather that thinking about how liquid moves through straws can help you to think about what is going on in your body. Those arteries of yours may be worth thinking about as you sip your cold brew this summer, whether or not you do so through a straw.
*The Hagen-Poiseuille law states that the flow rate F = ΔP.(r²)²/(8ηl) where ΔP is the pressure difference, r the radius of the straw, η is the viscosity of the liquid and l the length of the straw (or artery). Perhaps you can see why you will need a larger diameter straw to drink a milkshake.
†Blood Pressure Measurement, An Illustrated History by NH. Naqvi and MD Blaufox, Parthenon Publishing (1998)
A couple of weeks back, I tried the lovely Bond St. Coffee in Brighton on the recommendation of @paullovestea from Twitter. It was a Saturday with good weather and it turns out that this particular café is (understandably) very popular and so, sadly, to begin with we could only sit outside. That said, it was a lovely spring day (sunny but a bit chilly) and so it was quite pleasant to watch the world go by (or at least Bond St) while savouring a well made pour-over coffee. All around the café, the street decoration hinted at times past. Across the road what was obviously a pub in times gone by has turned into an oddities store. Air vents to a space underneath the window seating area in Bond Street café itself suggested an old storage space. A seat in the window appeared to have been re-cycled from an old bus seat.
But it was the pour-overs at Bond St. Coffee that had been particularly recommended and they certainly lived up to expectations. I had a Kenyan coffee roasted by the Horsham Roasters. The V60 arrived at our bench seat/table in a metal jug together with a drinking glass. The angle of the Sun caught the oils on the surface of the coffee, reminding me of Agnes Pockels and her pioneering experiments on surface tension. Pouring the coffee into the glass I thought about the different thermal conductivities of glass as compared to metal and how I had put both down on the wooden bench. How was heat being transferred through these three materials? And then, as I placed the metal jug back on the bench I noticed the reflections from the side of the jug and thought, just why is it that you can see through the colourless glass but the metal is grey and opaque?
Metal jug, glass cup. V60 presentation at Bond St Coffee
On one level, this question has a simple answer. Light is an electromagnetic wave and a material is opaque if something in the material absorbs or scatters the incoming light. In a metal, the electrons (that carry the electric currents associated with the metal’s high electrical conductivity) can absorb the light and re-emit it leading to highly reflective surfaces. In glass there are no “free” electrons and few absorbing centres ready to absorb the light and so it is transmitted through the glass.
Only this is not a complete answer. For a start we haven’t said what we mean by ‘glass’. The glass in the photo is indeed transparent but some glasses can be more opaque. More fundamentally though, there is a problem with the word ‘opaque’. For us humans, ‘visible’ light is limited to light having wavelengths from about 400nm (blue) to about 780nm (red). ‘Light’ though can have wavelengths well below 400 nm (deep into the UV and through the X-ray) and well above 780 nm (through infra-red and to microwaves and beyond). We can see the spread of wavelengths of light visible to us each time we see a rainbow or sun dog. Other animals see different ranges of ‘visible’ light, for example, bumble-bees can see into the ultra-violet. So, our statement that glass is transparent while metal is opaque is partly a consequence of the fact that we ‘see’ in the part of the spectrum of light for which this is true.
Sun dogs reveal the spectrum of visible light through refraction of the light through ice crystals.
For example if, like the bumble-bee, we could see in the UV, some glass may appear quite different from the way it does to us now. Even though the glass in the photo lacks the free electrons that are in the metallic jug, there are electrons in the atoms that make up the glass that can absorb the incident light if that light has the right energy. There are also different types of bonds between the atoms in the glass that can also absorb light at particular energies. The energy of light is related to its frequency (effectively its colour*). Consequently, if the energy (frequency/ wavelength) of the light happens to be at the absorption energy of an atom or an electron in the glass, the glass will absorb the light and it will start to appear more opaque to light of that colour. Many silicate glasses absorb light in the UV and infra-red regions of the electromagnetic spectrum while remaining highly transparent in the visible region. High purity silica glass starts to absorb light in the UV at wavelengths less than approx 160nm†. Ordinary window glass starts to absorb light in the nearer UV†. In fact, window glass can start to absorb light below wavelengths of up to ~ 300 nm, the edge of what is visible to a bumble bee: The world must appear very different to the bumble bee. At the other end of the scale, chalcogenide based glasses absorb light in (our) visible range but are transparent in the infra-red.
Looking at how materials absorb light, that is, the ‘absorption spectrum’, enables us to investigate what is in a material. It is in many ways similar to a ‘fingerprint’ for the material. From drugs discovery to archaeology, environmental analysis to quality control, measuring how a material absorbs light (over a wider range of frequencies than we can see) can tell us a great deal about what is in that material.
Perhaps you could conclude that whether something is opaque or crystal clear depends partly on how you look at it.
Bond St Cafe is on Bond St, Brighton, BN1 1RD
*I could add a pedantic note here about how the colour that we see is not necessarily directly related to the frequency of the light. However, it would be fair to say that a given frequency of light has a given ‘colour’ so blue light has a certain frequency, red light a different frequency. Whether something that appears red does so because it is reflecting light at the frequency of red light is a different question.
†”Optical properties of Glass”, I Fanderlik, was published by Elsevier in 1983.
It was my birthday a short while ago and someone who knows me well got me a perfect present: a kettle specially adapted for making pour-over V60 style coffees. Until this point I had been struggling with a normal kettle with it’s large spout but now, I can dream that I pour like a barista. Of course, it is important to try out your birthday present as soon as you receive it. And then try it again, and again, just to make sure that it does really make a difference to your coffee. So it is fair to say, that recently I have been enjoying some very good coffees prepared with a variety of lovely beans from Roasting House and my new V60/V60 kettle combination.
Spending the time to prepare a good coffee seems to make it even more enjoyable (though it turns out that whether you agree with this partly depends on why you are drinking coffee). Grinding the beans, rinsing the filter, warming the pot, the whole process taken slowly adds to the experience. But then, while watching the coffee drip through the filter one day, I saw a coffee drop dance over the surface of the coffee. Then another one, and another, a whole load of dancing droplets (video below). Perhaps some readers of Bean Thinking may remember a few months back a similar story of bouncing droplets on soapy water. In that case, fairly large drops of water (up to about 1cm wide) were made to ‘float’ on the surface of a dish of water that had been placed on a loudspeaker.
Sadly, for that initial experiment the coffee had been made undrinkable by adding soap to it. The soap had the effect of increasing the surface viscosity of the droplets which meant that the drop could bounce back from the vibrating water surface before it recombined with the liquid. Adding soap to the coffee meant that these liquid drops could ‘float’ (they actually bounce) on the water for many minutes or even longer (for more of the physics behind this click here).
A still from the video above showing three drops of coffee on the surface.
On the face of it, there are some similarities between the drops dancing on the coffee in my V60 and these bouncing droplets. As each drop falls from the filter, it creates a vibration on the surface of the coffee. The vibration wave is then reflected back at the edges of the V60 and when the next drop falls from the filter it is ‘bounced’ back up by the vibration of the coffee.
But there are also significant differences. Firstly, as mentioned, there was no soap added to this coffee (I was brewing it to drink it!). This means that the viscosity of the drops should be similar to that of ordinary water. Although water drops can be made to bounce, the reduced viscosity means that this is less likely. Secondly, the water is hot. This acts to reduce the viscosity still further (think of honey on hot toast). Perhaps other effects (such as an evaporation flux or similar) could be having an effect, but it is noticeable that although the drops “live” long enough to be caught on camera, they are not very stable. Could it be that the vibrations caused by the droplets hitting the coffee are indeed enough to bounce the incoming droplets back up but that, unlike the soapy-water, these “anti-bubbles” do not survive for very long? Or is something deeper at play? I admit that I do not know. So, over to you out there. If you are taking time to make coffee in a V60, why not keep an eye out for these bouncing droplets and then do some experiments with them. Do you think that the bounce vibration is enough to sustain the bouncing droplet – does the speed of pour make a difference? Is it associated with the heat of the coffee? I’d be interested to hear what you think.
(The original soapy-coffee bouncing droplet video).
If you see anything interesting or odd in your coffee, why not let me know, either here in the comments section below, e-mail, or over on Twitter or on Facebook.
As the name suggests, there is a lot of history behind the café at 3 Fleet St (the Fleet Street Press). Not only is it just around the corner from the Devereux (which was once the “Grecian” where Halley met Newton), it is a few doors down from the site of the second ever coffee house established in London (the “Rainbow” was at number 15). There is also plenty of history in the café itself. Fleet St Press operates from a listed building, considered especially noteworthy for its 1912 shop interior (ie. the café). The stained glass at the back of the shop (which was nearly the subject of this cafe-physics review) is apparently original while a sign (for “Tobacco blenders”) in the front window hints at the building’s previous use.
Inside, a row of tall stools offers seating along the wall while a large table at the front of the café offers a space to sit more comfortably to enjoy your coffee. We enjoyed a very nice long black (coffee from Caravan) and a soya hot (white) chocolate. The staff were friendly and it was a lovely space to spend a while. Keep-cups and other coffee making equipment are on sale just next to the counter and the café is just full of things to notice. It’s not just the stained glass. The window to the left of the main door has been stocked with a film camera with flash (presumably a nod to the Fleet St of old), an aeropress, a series of sand-timers and many other items of distraction. We sat at the window which had a good view towards the Royal Courts of Justice and two wonky K2 telephone boxes. Just across the passageway from the phone boxes was a post box and this got me thinking about communication and how we communicate with each other.
An interesting concept. A white chocolate hot chocolate made with soya milk
In an editorial to a book that rolled off one of Europe’s first printing presses, the Bishop of Aleria, Giovanni de Bussi wrote that printing could be considered an act of generosity “the act of sharing what was hoarded”*†. Since then, the newspapers of the old Fleet St have made way for coffee shops and the papers for the internet. The ‘snail mail’ post box across the road has been almost superseded by email or other forms of internet communication. The telephone box, replaced by mobile phones or Skype. Although we may feel overloaded with information, our ancestors felt the same way. Even in the 1640s it was claimed that they were living in times of a media explosion in which there were just too many books*.
So, rather than look at how the scribe gave way to the printing press, books to newspapers, letters to telegraphs and then telephones and now email, Twitter and instant messaging, perhaps it is worth dwelling a short while on what underlies all of these. Indeed, we are so used to what underlies these communication techniques that we may not even notice it.
Writing.
It may be an obvious point but none of these communication methods would have been possible were it not for writing. Given that Homo sapiens are thought to have come out of Africa some 200 000 years ago, and have been farming since 13000 – 8000 BCE, it is perhaps surprising that the first record that we have of a writing system was not until ~3500 BCE. Writing is thought to have originated in Sumer, Mesopotamia as pictographs. Phonographic writing was not developed until later. Shortly afterwards it was again ‘invented’ in Egypt (3150 BCE) and separately in China (1200 BCE) and MesoAmerica (~500BCE). Writing is a surprisingly recent phenomenon.
The view from the window at Fleet St Press
As with the fixtures at Fleet St Press, clues from these earlier cultures pervade the space around us rather like the ghost signs of advertising past. The tobacco sign above the door is suggestive of former occupiers Weingott and Sons. Famous for their pipes, they ran a shop on the site from the mid-nineteenth century until the 1930s. Meanwhile, the writing systems of the ancients lives on both in our alphabet and in our time keeping. Even the name ‘alphabet’ resonates with the history of the Greek “alpha, beta” and the Hebrew “Aleph, Beth” (themselves originating from the Phoenician). The Babylonian number system meanwhile, which dates from around 1800 BCE and used base 60 to count (i.e. rather than 1-9, their number system counted 1-59) echoes down the ages. It is thought that remnants of this system remain both in how we count the degrees of a circle (360) and how we tell the time (60 minutes in an hour, 60 seconds in a minute).
Signs and systems that are both instantly familiar and a ghostly ripple from the people of the past.
Fleet St Press can be found at 3 Fleet St, EC4Y 1AU.
*E.L. Eisenstein, “Divine Art, Infernal Machine, the reception of printing in the West from first impressions to the sense of an ending”, University of Pennsylvania Press, (2012)
†Quote from de Bussi is as quoted in Divine Art, Infernal Machine on p 15.
Some interesting anecdotes about the history of communication can be found in Robert Winston “Bad Ideas, An arresting history of our inventions” Bantam books, (2010),
Also recommended “A history of mathematics, from Mesopotamia to modernity”, L Hodgkin, Oxford University Press, (2005)
