Category: Science history

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General Observations Science history slow

Seeing things at a kopitiam (coffee shop)

Rocky, Bangsar, KL, Malaysia, koptiam
A kopitiam in Bangsar, Kuala Lumpur, Malaysia

One of the great things about travelling is exploring the different cafe and coffee cultures in different countries. Is it the coffee that is important? Or food, alcohol or maybe just the opportunity for socialising? In Singapore and Malaysia, the “kopitiam” (or coffee shop) is a familiar part of each neighbourhood. Each kopitiam serves local coffee (kopi) and a variety of foods which are usually prepared while you wait, from stalls around the edge of the kopitiam. The kopitiam provides a space for socialisation and meeting people over a bowl of steaming noodles. Inside electric fans are blowing continuously in an effort to lessen the heat. Frankly, the local coffee is not to my taste but there are plenty of other things to eat and drink in each kopitiam. A breakfast of “kueh” and black tea for example is a welcome change from toast at home! In many areas of Singapore, and to a lesser extent Malaysia, local kopitiams are closing to make way for the new style cafés which serve a range of freshly roasted, pour over or espresso based coffee. Not being Malaysian or Singaporean I do not want to comment too much on that, I guess it is similar to the decline of the “caffs” in the UK. Mourned by many in the community but welcomed by others for the improved quality of the coffee.

straw, water, glass
An everyday example of refraction. The water refracts the light to make the straw appear ‘broken’.

However, with so much going on in a kopitiam, the temptation to look at a kopitiam-physics review was too great, especially when I started to “see things” at the edge of the shop. Am I going mad? No, it was not that my imagination was playing with my mind; I saw the ingredients for a mirage. You see, at the edge of the kopitiam the hawkers will cook noodles, or rice dishes etc. and this creates heat. Above some stalls there will be clouds of steam rising as the noodles boil in a pan. The clouds appear white because of the scattering of light by reasonably sized water droplets (more info here and here). Above other stalls, there is no steam but the heat created by the cooking makes the air immediately above the stove warmer (and therefore less dense). This less dense air refracts light less than air at room temperature. It is refraction that causes that straw in your iced coffee to look as if it is broken as you look at it (see picture). In the kopitiam, it means that as you look through this region of warm air you see a wobbly or wavy type pattern as the light from outside is refracted by different amounts depending on the temperature of the air that it goes through. It is this that is the primary ingredient for seeing a mirage.

The fact that air at different temperatures refracts light by different amounts is the reason for mirages in the desert. Frequently, warm air is trapped at ground level by a layer of cold air above it. The light is bent as it travels through these layers (see diagram here) and so it may appear as if they sky is on the ground (which the brain will interpret as a pool of water on the ground). Conversely, if there is a layer of cold air trapped beneath a layer of warm air, the light is bent downwards and so objects that are usually below the horizon due to the curvature of the earth can be seen (illustrated by the diagram here).

Edmond Halley, Canary Wharf, Isle of Dogs, view from Greenwich
The view towards the Isle of Dogs (and Canary Wharf) from Greenwich. Things have changed a little since Halley’s time.

Back in 1694 Edmond Halley (who drank coffee with Isaac Newton at the Grecian) was investigating the evaporation of water as a function of temperature. He wanted to see if evaporation alone could explain the rainfall and the quantity of water in the river system. As he did so he noticed that, in still air, there was a layer of water vapour that formed above the bowl of evaporating water. He noticed this because it refracted the light in an unusual manner. At the time, there was reported to be an unusual phenomenon that occurred at high tide near Greenwich. It seems that cows used to graze on the Isle of Dogs in London. Ordinarily the cows could not be seen from Greenwich because they were too far away, but occasionally, at high tide, the cows would be visible. Putting together what he knew about the evaporating water Halley wrote “This fleece of vapour in still weather… may give a tolerable Account of what I have heard of seeing the Cattle at High-water-time in the Isle of Dogs from Greenwich, when none are to be seen at low-water (which some have endeavoured to explain by supposing the Isle of Dogs to have been lifted by the Tide coming under it.) But the evaporous effluvia of water, having a greater degree of refraction than the Common Air, may suffice to bring these Beams down to the Eye, which when the Water is retired, and the vapours subsided with it, pass above, and consequently the Objects seen at the one time, may be conceived to disappear at the other”*. I think that although he had the mechanism correct (in terms of refraction), the cause of this odd refraction was temperature inversion and a layer of cold air immediately above the Thames rather than water vapour but what do you think? Let me know in the comments section below.

 

* Punctuation and capitalisation kept as in original. Taken from Edmond Halley, “An Account of the Evaporation of Water, as It Was Experimented in Gresham Colledge [sic] in the Year 1693. With Some Observations Thereon” Phil. Trans. 18, 183-190, 1694″

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cafe with good nut knowledge Coffee review General Observations Science history

Thinking of foraging at Damson & Co

Damson and Co, like its wild counterpart, easy to miss
Damson & Co on Brewer St.

At approximately this time of year, it is possible to start foraging for damsons in the UK countryside. These small plums make lovely cakes and muffins and, very importantly, great damson gin. A bit like sloe gin but, in my opinion, better. All this is a digression. When I found out about a cafe called Damson & Co I had to try it, purely for the name which brings back fond memories of country walks and gin shared with friends. However, even armed with its address and location on a map I missed it! Damson & Co is very inconspicuous in the way that it is situated on the street. Just as with its wild counterpart, it is easy to walk past without noticing that it’s there but once you’ve seen it, it is obvious, a location that you mark down in order to return to it again and again.

Inside, lavender decorated the table tops in the small but extremely friendly cafe. We enjoyed an Americano, an iced latte and a lovely chocolate brownie that had been warmed almost to the point of melting. They were also extremely helpful when I asked the dreaded “does it contain nuts?” question, checking the ingredients, informing me of the (obligatory) “it may have had contact with a nut at some point in its manufacture” line, but ultimately helping me to choose what was a great nut-free cake. Complementary water was automatically put onto the table and so we had, for the brief moment before I ate the cake, a range of ‘phases of matter’ on the table. Water in the forms of liquid in the bottle, solid ice and steam rising up from the coffee and a brilliantly gooey, viscous chocolate cake somewhere between liquid and solid. At that point it was quite clear what the physics bit of this cafe-physics review would have to be: phases of matter and phase changes.

interior of Damson & Co
Lavender in a jar with sugar in the window of Damson & Co

As ice melts into water, or evaporates to form steam, it undergoes many changes in its properties: Ice is of course solid; liquid water conducts heat much readily more than steam (more on this another day). Another property that changes is the heat capacity of the ice/water/steam. The heat capacity is the amount of energy that it takes to heat a substance by one degree in temperature. At the temperature that the substance changes, say between a liquid and a solid, there will frequently be a spike in a plot of “heat capacity” vs. temperature. This tells us that, as the solid changes to a liquid (or vice versa) the response of the material to being heated changes. Physicists often measure the heat capacity of substances to see if any phase changes occur. A phase change does not necessarily mean that the substance goes from liquid to solid or to gas. A substance will be said to undergo a phase change if it becomes ferromagnetic (like iron at room temperature) or if it becomes superconducting (like aluminium at approximately -272C). Back in the 1920s it was the investigation of the heat capacity of liquid helium that helped to suggest that there was a new form of matter lurking at extremely low temperatures.

Heike Kamerlingh Onnes (a great physicist and apparently a very nice man) had managed to liquify helium gas in 1908. Helium gas becomes a liquid below -269C. By the 1920s it was clear that something very strange happened to liquid helium if you cooled it even more, to temperatures below -271C. The behaviour of the heat capacity spiked indicating that the helium was undergoing another phase change, but to all appearances it was still a liquid. There was no indication that the helium was solidifying, what could it be? More experiments revealed that below -271C the helium liquid started to behave very strangely indeed. It climbed up the walls of its container ‘by itself’ and it managed to leak through minuscule cracks in the glass containers that it was kept in (for a video click here). Cracks that could not be detected before the ultra-cold helium started to leak through them. It took until 1937/38 before this new state of matter was named and it is still not clear that we understand it.

There is so much more to the phases of matter than meets the eye while watching ice melt in a glass of water on a hot summer’s day.

Damson & Co can be found at 21 Brewer St. London

Categories
Coffee review Observations Science history

Enlightenment at Timberyard, Seven Dials

coffee, Timberyard, wooden tray
Great coffee at Timberyard

It is not often that you come across an independent café in central London that has great coffee, a good deal of space and seats available and so I found myself very happy to have come across Timberyard near Seven Dials. As I ordered my long black, I was presented with a choice of bean for the espresso base. Should I have the “fruity and acidic” Jabberwocky, or the “chocolate” Climpsons? I was trying Timberyard for the first time and so the choice was easy. For me ‘chocolate’ will win over ‘fruity’ every time. However having the choice was a nice touch. Being in central London, it was of course crowded when I tried it, but there were still seats around, including some stools outside. I took a seat outside, ready to watch the people and the cars going by. After a short while, the coffee was brought over, served on a wooden tray together with a complementary bottle of water.

crema on coffee, Timberyard
The patterns as the crema breaks up are reminiscent of the coastlines of Norway and of fractal mathematics.

It was a very pleasant location to sit and enjoy my coffee while I watched people rushing by on their way to various meetings and tourists milling around, taking their time to soak in the city. As I waited for the coffee to cool, the crema on the surface started to break up and I was reminded of the coastline of Norway. It struck me that the same mathematics of fractals describes the coastlines as would describe the patterns in the crema. It was then that I noticed the street lighting. A light converted from an old style gas lamp was attached to the wall of a shop just across from where I was having my coffee. In the other direction, there was a modern lamp-post of one particular design and then, just slightly further down the road, a lamp-post of a different design. This prompted me to think about the history of street lighting and also the problems with it.

One of the first roads in England to be lit at night was the Route du Roi (nowadays known as Rotten Row) that ran from Kensington Palace to St James Park. Three hundred lamps were hung from trees along the route. These first street lights produced light by burning fuel, a method of street lighting which existed in one form or another until fairly recent times (as evidenced by the oldest street lamp visible from Timberyard). They were installed, as now, to try to reduce crime; it seems that the park used to be frequented by highwaymen. One of these had been hanged for the killing of a woman in the park in 1687. Though it wasn’t quite murder: Rather than be robbed of her wedding ring, the unfortunate lady had attempted to swallow it and so choked to death.

gas lamp, Monmouth St
An old style street lamp on Monmouth St. visible from Timberyard

A more recent type of street light was based on sodium. Applying an electric voltage across a gas of sodium caused the sodium to emit light in the yellow region of the visible spectrum. If rather than sodium, the lights had been based on neon gas, the colour of the light emitted would have been different as the colour corresponds to the different energy levels in the atoms, (for more info click here). In an effort to find increasingly efficient light sources, there is now a move into street lighting based on LEDs (Light emitting diodes). Rather like the sodium lamps, such devices work by applying a voltage over a material but in the case of the LEDs, the material is a semiconductor junction (where the energy gap can be manipulated to have the same size as the energy of visible light). LEDs have the significant advantage that the voltage supplied to produce sufficient lighting can be much less than is the case for sodium lights. This increase in efficiency is a small but effective way to limit our carbon dioxide emissions, especially when used together with sensors on the lamp post to detect when it is dark enough to actually necessitate the light being turned on.

Such a combination of energy saving measures benefits not just the planet but the public wallet. Perhaps in a few years time we’ll see such a set of eco-friendly lamp-posts spring up near Timberyard to add to the collection of street lights there.

In the meanwhile, if you visit Timberyard and notice some interesting physics or history, or if you just slow down and see something interesting, please let me know using the comments box below.

Timberyard is at 7 Upper St Martin’s Lane, Seven Dials, WC2H 9DL (and Old St, EC1V 9HW.)

London info taken from The London Encyclopaedia (3rd Ed), Hibbert et al.

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Coffee review Observations Science history slow

Bridging worlds at White Mulberries, St Katherine’s Docks

chalkboard at White Mulberries
Sign board at White Mulberries.

Five minutes walk from the Tower of London is an area that feels far removed, physically and metaphorically, from the crowds swarming around the central tourist sights. St Katherine’s Docks offer a peaceful retreat a stone’s throw away from the bustle of the Tower. And if you are in this area, there is no better place to have a coffee (and potentially a cake) than White Mulberries. This café looks over the central basin of the three docks in St Katherine’s and is, seemingly, in the only 19th century warehouse still standing in the docks. On each occasion I have visited White Mulberries the coffee has been very good. As a black coffee drinker, the taste of the coffee has to be great as there is no hiding a bitter espresso with the milk of a latte and White Mulberries has passed every time (their website says that they rotate the coffee roasters, so I can only assume that they have a great relationship with their suppliers). If Latte Art is your thing though, White Mulberries also has that. It was an example of the latte art at White Mulberries that accompanied my recent article in Physics World.

Bascule Bridge, St Katherine's Docks
A moving bridge at the entrance to St Katherine’s Docks. There are youtube videos of this opening.

The point of a “café-physics” review on Bean Thinking though is only partly about the great coffee on offer (all cafes that are featured in the Daily Grind have great coffee). Part of the point of a café-physics review is to look around, slow down and notice things and see what physics there is around the café in question. There is always something to notice, always something science-like to appreciate. White Mulberries is no different, with an enormous number of things to notice, from the water in the docks to the Aeolian harps made by the rigging on the yachts moored nearby. What I would like to concentrate on today though are the bridges. Bridges are often used in scientific outreach with children. I think it is partly because so many concepts in physics can be communicated by practising making bridges. Forces need to be balanced (Newton), stress and strain needs to be considered, the properties of materials are unconsciously learned. And this, I think is another reason that bridges are a great ‘outreach’ tool, because bridges are inherently multidisciplinary. To make a good bridge requires elements from physics, chemistry, mechanical and civil engineering and art to name just a few. A bridge needs to satisfy the aesthetic demands of the public that use it as well as the structural demands of the people that will stand on it. And the bridges in the docks required yet more work and more understanding, for these aren’t just bridges that span a waterway, these bridges need to move somehow to allow boats to pass, either by having a platform that rises up (as with the nearby Tower Bridge), or platforms that swing around (which was the design of some of the original bridges at St Katherine’s Docks). Great thought and understanding went into the design and building of these mechanisms for moving the bridges. There is much to be gained by contemplating bridge design.

Microcord image of Tower Bridge with tourist in foreground
Tower Bridge, Photo © Artemisworks Photography, http://www.artemisworks.plus.com

Which brings us to another bridge, this time a metaphorical one between White Mulberries and the Coffee Houses of the past. The designer of St Katherine’s Docks was Thomas Telford (1757-1834). As well as specifying the design of the docks, he was responsible for some of the original bridges in the docks themselves, particularly a swing bridge that was built in 1828. St Katherine’s Docks was Telford’s only London project but that didn’t stop him from being a regular in a Coffee House near (what is now) Trafalgar Square. For many years Telford drank coffee in the Salopian Coffee House (most likely in Spring Gardens, just behind Cockspur St). This was where he stayed when in London and, as he was a famous engineer by that point, he started to attract crowds of engineers and admirers to the Salopian in the hope of meeting him. So important was Telford to the business of this central London coffee house that, when he left to live in Abingdon St, the new landlord of the Salopian complained to him “What, leave the house? Why sir, I have just paid £750 for you!”.

Fortunately, White Mulberries has far more to attract customers to it than one illustrious coffee drinker, though perhaps it has those as well.

 

White Mulberries is at St Katherine’s Docks, E1W 1AT,

A good book on bridges is: “Bridges – the science and art of the world’s most inspiring structures”, David Blockley, Oxford University Press (2010)

Coffee House anecdotes from “London Coffee Houses”, Bryant Lillywhite (1963)

Categories
Coffee review General Science history Tea

All in a Glaze at Straits Times Kopitiam

Straits Times KopiTiam, outsideDespite the name, “Straits Times Kopitiam” is in Aldgate, London. Kopitiam translates to “coffee shop” and they can be found throughout Singapore and Malaysia. It’s not just coffee though, Kopitiams traditionally sell a wide range of fantastic noodles & rice dishes which will be taken for breakfast or lunch while chatting with friends. A couple of large communal tables in this Aldgate kopitiam provide the space for sitting down and chatting with your neighbours, while the selection of food on offer is very western, with sandwiches and cakes replacing some of the more typical Asian dishes. Although this is a bit of a shame, it is perhaps understandable. Hopefully, as time goes on we will get more great SE Asian food here and it will become more economically viable to sell it. Still, the Straits Times Kopitiam is, just as its SE Asian namesakes, a place where you can sit and enjoy a drink in very friendly surroundings. As we were sitting there, various people came in to chat about the crayon drawings on the wall at the back while messages were suspended on bits of string around the sides of the cafe. Such touches add to its friendly, almost intimate, social atmosphere. You may not know who roasts the coffee here but where else could you get a Teh halia (a type of tea with ginger), a hot chocolate with chilli or, a Milo Dinosaur (if you like iced drinks it is probably better for you to try it rather than have me describe it)?

enamel mug, teh halia, Straits Times kopitiam
An enamel mug containing Teh halia

A feature common both to the Straits Times Kopitiam and many such places in SE Asia though is the cups, enamelware cups with a navy rim. Such cups were apparently ubiquitous until fairly recently when they faded from fashion, though they are now back in a type of retro-chic, Singapore style. The great advantage of metal cups was that they were cheap and easy to produce. So in a world before plastic, a metal mug was the way to go. That said, metal crockery and cookware can tend to rust, or look a bit ugly and so the cheap metal cups were often enamelled to produce the type of mugs that are now used in Straits Times Kopitiam.

The story of how the mugs are enamelled leads us to the story behind the Giant’s Causeway in Northern Ireland. How? Well, enamelling uses the fusing of a glass onto the metal by heating it to approximately 800 C. Glass can be quite transparent and colourless so what gives it the white and blue colouring of the mugs used in the Straits Times Kopitiam? The blue is fairly easy, it is caused by the addition of metal oxides such as cobalt, but the white? That is harder to pin down and although some investigation suggested that some chemical additives could be used to make the enamel more opaque, it was also suggested that the opacity of the white enamel is due to the crystallisation of the glass.

Giants Causeway, lava crystals
A view of the Giant’s Causeway, taken by Jim “code poet” and shared under Creative Commons attribution license. Original  file location:
https://www.flickr.com/photos/alphageek/20005235/

When a substance is heated above its melting point and then cooled, crystals can grow in it, the size and shape of which depend on the heat treatment of the material, for example how fast you cool it from its melting point. For enamel the material is glass but this crystallisation process can also be seen in chocolate. The heat treatment makes the difference between the formation of long crystals that give chocolate a hard, crisp sheen and smaller crystals that make the chocolate more dull, which is why the technique of tempering chocolate is so tricky. James Keir (1735-1820) wrote a study in the Royal Society’s journal Philosophical Transactions that described how glass crystallised as it was cooled. In particular he noted that cooling the glass slowly from its molten state produced a white and opaque type of glass that was at the time being called Reaumur’s porcelain. By studying the shape, form and cause of these crystals in glass, Keir made a sudden extrapolation: could the regular shapes of the Giant’s Causeway or the pillars of Staffa be caused by crystallisation of molten lava? This is indeed the explanation that we now have of the Giant’s Causeway*. Rather than being put into place step by step by a road building giant, the slow cooling of molten lava produced the crystal structures that are now visible on the shoreline.

Concerned that it would be thought that the had overstated the connection from glass to molten lava and geological features, Keir wrote at the end of his paper:

“No just objection can be drawn against this analogy from the magnitude of the former [lava] compared with the minuteness of the latter [glass]: for the difference of size between the small vitreous crystals and the stupendous basaltic columns, which support mountains, islands, and provinces, is no more than is proportionate to the difference usually observed between the little works of art and the magnificent operations of nature“.

Does any more need to be said?

Straits Times Kopitiam is at 66A Whitechapel High Street,

“On the crystallizations Observed on Glass. By James Keir, Esquire, of Stourbridge. Communicated by G. Fordyce, M.D.F.R.S” Phil. Trans. R. Soc. Lond., 1776, 66, 530-542

* Note added 21 Oct 2015. It seems that we’re still debating how the Giant’s Causeway was formed. A recent article (here) suggests it is about how things crack as they cool rather than about how crystals form. However, the link to cooling glass and cooling ceramics remains. Keir was certainly on to something.

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Coffee review Coffee Roasters Observations Science history slow

Wonders of the World at Espresso Base, Bloomsbury

Hasten coffee, long black, black coffee, espresso base
‘Has Bean’ coffee at Espresso Base

Espresso Base is exactly the sort of café that you want to make sure that you know about, but part of you is selfishly quite happy if not too many others do. It is not that the the place is small, far from it. There is plenty of space in the courtyard at Espresso Base, beside St George’s Church, to sit and enjoy your coffee. The thing is, it is great to have the place almost entirely to yourself. With few others around, the oasis-like quality of the place is emphasised, astonishing as it is so close to the busy Bloomsbury Way. Only this oasis serves great coffee. Their coffee is roasted by Has Bean, which I admit is the reason that I first dropped into Espresso Base a few weeks ago. The black coffee that I had was certainly very good and the environment in which to enjoy the coffee was thought provoking which, for me, is an important aspect of any café. Cafés need to be places that you can go, slow down and notice things and Espresso Base certainly falls into that group of cafés that I would highly recommend both for the coffee and the café.

stone recycling, slate, slate waterfall, geology
The purple slate waterfall feature in the courtyard area at Espresso Base. You can just see the stone with the rectangular holes carved into it at the bottom of the wall.

On the day that we arrived, it had been raining. For a café with seating outside this may have posed a problem but the chairs had been thoughtfully folded so that they remained dry. The rain had however seeped into some of the paving slabs around the chairs and so that was the first thing to notice, the fact that many objects when wet appear darker, why? Opposite our seating was a rock feature that to me looked like a waterfall made out of slate, the slate had a purple tinge which again, had been made slightly more purple by the rain. Below the slate ‘waterfall’ and forming a wall, were a series of stones that had clearly been taken here from somewhere else. I say ‘clearly’, because the stone at the bottom had two holes that had been carved out of it, one square, one slightly more rectangular. Presumably the stone had been used as part of a gate post in the past and yet there is no evidence of the remains of a gate on the other side of the courtyard (I think that a gate post would have to be deeper than the square indent in the paving slab that is at the other side of the courtyard). It is therefore more likely that the stone had been used somewhere else beforehand and ‘recycled’ for use in this wall. This juxtaposition of slate above and recycled stone below reminded me of the early geologists and how they identified the Great Glen fault that runs through Loch Ness in Scotland. Slate is a metamorphic rock, meaning that it has undergone changes due to the high pressure and temperatures within the Earth. Slate is however quite a low-grade metamorphic rock so, compared with higher grade metamorphic rocks, it has not been subjected to that much pressure or that much temperature. By mapping the lower grade and higher grade metamorphic rocks along the Great Glen, the early geologists noticed a line that sharply separated the metamorphic rock types. This fault would have, in the past, caused earthquakes as the ground slipped along the fault.

Replica of Mausoleum of Halicarnassus
The steeple of St George’s church, Bloomsbury Way. The statue on top is of King George I rather than King Mausolus in  his chariot. The statue of Mausolus, his wife/sister Artemisia and a horse from his chariot can be seen in the British Museum.

On leaving Espresso Base I turned and looked up at the church. If you get a chance, take a look at the steeple. Particularly ornate, the stepped steeple is apparently built to the description of the Mausoleum of Halicarnassus by Pliny the Elder. This monument was one of the seven wonders of the Ancient World and was built to be the burial chamber of King Mausolus of Karia. Described as standing approximately 40 m in height, this massive stepped, marble pyramid stood on top of 36 columns surrounded by statues. Topping the pyramid was a statue of King Mausolus himself, in a chariot. This ancient wonder is thought to have been destroyed by an earthquake in the fourteenth century after which the stones were ‘recycled’ by the Knights of Malta to build a fortress. A history that is aptly mirrored in the geology and stone recycling evident in the courtyard of Espresso Base.

 

Espresso Base can be found in the courtyard of St George’s church, Bloomsbury Way, WC1A 2SE

Artefacts from the Mausoleum of Halicarnassus can be seen in room 21 of the British Museum (conveniently just around the corner from Espresso Base).

Geology help from: “Geology Today, Understanding our planet”, Murck/Skinner, John Wiley & Sons, 1999

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cafe with good nut knowledge Coffee review Observations Science history

Crystal Perfection at Workshop, Holborn

Workshop coffee Holborn
Diamonds are forever, Workshop coffee Holborn

The brand identifier of Workshop coffee is a diamond, a representation of which hangs on the wall as soon as you enter the Holborn branch. I had arrived at Workshop in order to try their coffee after I’d had a great espresso made with beans roasted by Workshop at Knockbox in Lamb’s Conduit Street. The coffee brewed in their own café certainly did not disappoint. I enjoyed a very good La Soledad filter coffee and a cake (which was confidently nut free, this brings me to another plus point for Workshop, they know the ingredients of their cakes!). The interior of the cafe, just beside Holborn Viaduct, is quite spacious and, if you sit at the back, you get a great view of the workings of the espresso machine as different people come in to get their ‘take out’ coffee. It is very possible to spend quite some time here in order to relax and enjoy your coffee while taking in your surroundings. To a physicist who studies materials (like me), the diamond logo of Workshop represents a fantastic material. A material in which the structure of the crystal determines so much about its properties. Were the carbon atoms in diamond bonded slightly differently, they would form the soft, pencil lead material ‘graphite’, rather than the hard, transparent material of diamond.

unit cell, repeating structure
The floor at Workshop reminds me of my crystallography text books.

Whether it was intentional or not, the crystal theme of the logo was replicated in the floor tiling of the Holborn branch. Crystallography is a branch of science that probes the building blocks of solids. It reveals how the atoms that make up different solids are arranged to form the solid. The atoms could be arranged in a simple cubic arrangement (as with salt) or hexagonally (as is the case for graphite). To establish the crystal structure you need to find the smallest repeating unit in the whole. Many introductory solid state physics or crystallography text books use 2D examples of repeating structures to help the student to understand how to build up these “unit cells” into full blown crystals. Many of the examples of such lattices look stunningly similar to the floor at Workshop.  Fundamentally, the idea of the crystal is that it is a simple repeating structure, just like the floor of Workshop. Indeed, the word “crystal” as used by Pythagoras implied perfection, harmony and beauty, a sense that is really conveyed by the crystal structure of the diamond logo of Workshop.

Crystal cake, LaFeSi cake, grape atoms
When a colleague left our lab, we made her a  cake that was a representation of part of the crystal structure of the material that she had worked on. Chocolate grapes and profiteroles represent different atoms in the structure.

The ancient Greek term for “crystal” actually implied the type of hard ice that is wonderfully clear and transparent. And it is ice that connects the area surrounding Workshop with a famous chemist who won a Nobel prize for his work in crystallography in 1962.  Max Perutz (1914-2002) described crystallography as a technique that “explains why diamond is hard and wax is soft, why graphite writes on paper and silk is strong”. Once you have enjoyed your coffee at Workshop, if you head down the stairs on the viaduct and descend to Farringdon Road you quickly get to Smithfield Market. It was here that, during the Second World War, Perutz helped to develop the material Pykrete. A “secret weapon” of World War II, Pykrete was developed five floors below Smithfield Market in a room cunningly disguised with animal carcasses. The planners in the war effort had wanted to design a boat made of ice but the problem was that when it was shot at, ice shattered. Could scientists develop a type of ice that would not shatter if it got hit by enemy fire? Pykrete was the answer. Pykrete uses the fact that materials such as plastics can be strengthened by adding fibres to them. In the case of Pykrete the “fibres” were sawdust and the material to be strengthened was ice. Not only does it not shatter when shot at (instead, the bullet creates a crater in the ‘boat’), it takes a lot longer to melt than ordinary ice. The sawdust encased in the ice acts to insulate the ice and increase its longevity.

Perutz’s Nobel prize was for his work to determine the crystal structure of haemoglobin, it took ‘just’ 25 years to do so. The field of crystallography continues to enrich our understanding of the behaviour of solids, though now we’re expected to get results more quickly than the 25 year time frame Perutz enjoyed. If you know of a good café where lots of physics goes on, or of a good café near a site of special (or unexpected) scientific interest, (or even just a good café) please do share your story either in the comments section below or by contacting me on email, Twitter or Facebook.

Workshop Holborn is at 60 Holborn Viaduct, EC1A 2FD

Quotes and other useful facts taken from:

“In our time, 29th November 2012: Crystallography“, (BBC Radio4)

Max Perutz “I wish I’d made you angry earlier” (2002),

Ichiro Sunagawa “Crystals, Growth Morphology and Perfection”, Cambridge University Press (2005)

Categories
Coffee review General Science history

Getting some perspective at Skylark, Wandsworth

Skylark Wandsworth
A sunny day at the Skylark on Wandsworth Common

It is late spring in the northern hemisphere and when the weather is fine, what better way to spend it than with a coffee in the middle of Wandsworth Common at the Skylark Cafe? With a number of tables outside and, if the weather turns bad, several more tables inside, Skylark is a lovely place to spend some time while wandering in West London. On the day that we were there, Skylark was frequented by a large number of families however, it was a Saturday afternoon and so it is quite possible that on a week-day it will be a bit quieter. The coffee is roasted by Caravan and they have an interesting array of cakes inside, but it was the plants on the tables outside that caught my attention. Each table had a pot of thyme on it, but the thyme smelled of lemon. Perhaps it was lemon thyme, but something that looks like one thing and smells of another is a nice introduction to this week’s Daily Grind which is all about appearances, reality and perspective.

The thyme was growing in a metal flower pot which reflected the wooden table top. From the photo (below, left), it is clear that the pot is cylindrical but if we stop and think about it, how do we actually know that? The image is two dimensional, no third dimension is possible through a computer screen. What clues in the picture tell you that the pot is cylindrical? The bending of the lines of the table top? This is a pattern that we have learned, we have found from experience that something that is circular will bend straight lines in this way.

perspective, flower pot
What shape is the flower pot?

How we see things and what we think we are seeing was a subject that bothered George Berkeley (1685-1753). How can you know that anything external to yourself is real? Everything you touch, everything you see, hear, taste or smell is, ultimately, a response in your brain to a stimulus. It is not easy to prove that anything ‘outside oneself’ really exists. Indeed, Berkeley argued for the theory that what was ‘real’ was only the sensations in your mind. The theory was famously challenged by Dr Samuel Johnson (1709-1784) who used to drink coffee at the Turks Head in Gerrard St. in what is now Chinatown. Johnson hurt himself by kicking a stone, while saying of Berkeley’s theory: “I refute it thus“. Does Johnson’s sore foot really refute the theory though? How can we avoid Berkeley and find our world again?

Writing about science at the turn of the twentieth century, Pierre Duhem (1861-1916) argued that “All the time we view scientific theory as an attempt at an explanation, we will be limited in what we consider an acceptable explanation by our metaphysical beliefs. Only by accepting that theory is in fact a description, a cataloguing, do we free ourselves from all but the primary metaphysical belief that the world exists“. In other words, in order to ‘do’ science we have to rely on (at least) two beliefs a) that the world outside exists, b) it is consistent, that is, governed by laws that are knowable. Neither of these premises can be ‘scientifically’ proven, instead they lie at the base of our belief system, even if we do tend to take them for granted. It is far easier after all to live in the world, if we assume that it exists.

Americano, Caravan coffee, Skylark, Wandsworth
Coffee at the Skylark

None of this should stop us doing science. Whatever we are investigating with our experimental (or theoretical) tools it is beautiful and the more that we understand the mathematics that describe the world, the more beautiful the world outside becomes. I cannot prove, scientifically, that the world outside exists, I could possibly argue that it does based on philosophical ideas but I will never be able to prove it. I understand that the pot on the table at Skylark is a three dimensional cylinder because of the way that the light is  bent on reflection and from my, admittedly intuitive, understanding of perspective. Perhaps we also need some perspective in appreciating what we can, and cannot, prove with science.

 

Skylark Cafe is on Wandsworth Common.

Quote taken from “The Aim and Structure of Physical Theory”, Pierre Duhem, 1910.

Categories
Coffee review General Observations Science history

Molecular reality at the Turkish Deli, Borough

“Just as the air is more dense at sea-level than on a mountain top, so the granules of an emulsion, whatever may be their initial distribution, will attain a permanent state where the concentration will go on diminishing as a function of the height from the lower layers, and the law of rarefaction will be the same as for the air” (Jean Perrin)

Turkish Deli, Turkish Coffee
The Turkish Deli, Borough Market

I have long had a fascination for the history of coffee and the different styles of brew. So it should be no surprise that I went to try The Turkish Deli in Borough Market for the Daily Grind. Very close to Monmouth, the Turkish Deli serves Turkish-style coffee and a delicious looking array of Turkish delights. Although quite far from the brew bars and single estate coffee types of some cafés now in London, Turkish coffee nonetheless offers the opportunity to slow down and appreciate the moment. Perhaps even more so than an espresso, since you are forced to wait for the coffee to be ready. The coffee is presented to you, straight from the Ibrik, in a small cup with a fantastic looking crema on top of it. At this point you are told that you will have to let it settle for at least four minutes before even thinking about starting to drink it. Indeed, the person in front of me in the queue was advised that he could “sit down, watch the world go by” while waiting for the crema on the coffee to turn a very dark (black) colour, indicating that the coffee was finally ready.

before settling, Turkish coffee
Waiting for the coffee to be ready

If you take sugar in your coffee you have to add it right at the start, before the coffee is warmed to the point of boiling (though it is not boiled). The reason is fairly obvious if you think about it. Turkish coffee has a large amount of sediment, this is the reason that you need to leave it for four minutes for the sediment to ‘settle’. Adding sugar during this settling time would mean that you would need to stir the coffee which would disturb the sediment and prevent it from quickly settling. Instead, you either take your coffee sugar-less or you add your sugar before starting this settling process.

Jean Perrin, (author of the quote at the start of this week’s Daily Grind) used the gradient of sediment in a different liquid (gamboge – a bright yellow paint pigment) to confirm the existence of molecules, just over one hundred years ago. He was exploring Brownian motion, the seemingly random motion of bits of dust, sediment etc, on the top of the coffee cup which had been explained in terms of “molecules” in the coffee (or water, or paint), hitting the bits of dust on the surface. Jean Perrin (1870-1942), realised that if Brownian motion was being caused by molecules, they would not just be causing the movement of the dust (and sediment) on the surface, it would be a three dimensional effect. Measuring the gradient of sedimentation would be a way to prove the molecular theory of Brownian motion and, simultaneously, to prove the existence of molecules.

Turkish coffee
The surface of the coffee reminded me of a coastline, itself connected (mathematically) to Brownian motion

Imagine a bit of sediment in the middle of the liquid (it could be a Turkish coffee, for Perrin it was the paint). That piece of sediment is going to be pulled down by gravity but in addition, it is going to be pushed up by molecules from below and down by molecules in layers above it. This is the bit that is related to Brownian motion. We know that even after leaving it for a long time, much of the sediment is still suspended mid-way up in the cup. It follows that the total forces acting downwards on the sediment (from gravity and the molecules above it) must be the same as the total force acting upwards (from the molecules below).

This means that the mass of sediment held at any particular level in the coffee must decrease with height. If the size of each piece of sediment is identical (which was ensured by Jean Perrin in his paint but is not the case for the Turkish coffee), then the number of pieces of sediment held aloft in the coffee/paint would decrease with height from the bottom to the top. All Perrin had to do therefore was to count (with a microscope) the number of bits of sediment as a function of height in order to test whether the molecular theory for Brownian motion was correct.

Turkish coffee, Borough market, sedimentary, sedimentation
The sediment at the bottom of the cup, don’t drink this bit!

To obtain statistics, Perrin and his assistants would count 11000 particles in one emulsion and repeat this experiment 1000s of times, but his patience paid off. By 1910, (only a few years after starting his observations), Perrin could claim that “the molecular theory of the Brownian movement can be regarded as experimentally established, and, at the same time, it becomes very difficult to deny the objective reality of molecules”. In 1926 he received the Nobel prize in recognition of this work.

Returning to the coffee, it is a very good drink with which to slow down and watch the world go by, perhaps while pondering molecular reality. When you get towards the bottom, do not drink the sediment but do take time to appreciate the mouthfeel and flavour as you drink this beverage that, in many ways represents an early chapter in the coffee story and one that continues to be made very well at the Turkish Deli.

The Turkish Deli is in Borough Market, Stoney Street, London, SE1 9AA

Quotes taken from “Brownian Movement and Molecular Reality”, Jean Perrin, 1910

Categories
cafe with good nut knowledge Coffee review Science history slow

Spinning a yarn at E&J’s Pantry, Endell St.

E&J's Pantry on Endell St
E&J’s Pantry on Endell St

There are still a few areas of central London which seem a little short on good cafés. One such area lies just east of Covent Garden. So it was very fortunate that, on arranging to meet a friend nearby, I came across E&J’s Pantry on Endell St. The coffee is from Nude roastery and the interior, while not exactly spacious is large enough that we were able to sit undisturbed for quite some time. Along with good coffee, they serve lovely cakes which (according to their website) are made in their own kitchen. This is presumably why they could tell me confidently which cakes were nut free. (Those who follow @thinking_bean on Twitter may know that this is a bit of a hot topic for me.) I enjoyed a very good Long Black and a cake, before sitting back and taking in the surroundings.

On one of the walls inside E&J’s Pantry are a series of photographs. Each photograph is suspended by a thin thread from a rail near the ceiling. The observation reminded me of spiders webs and the (often heard) claim that spider silk is a natural material that is “stronger than steel”.

photographs, spiders web, nylon
Photographs inside E&J’s pantry. Can you see the thin threads holding up the pictures?

Unfortunately, the claim that “spider silk” is stronger than steel is a little disingenuous. For a start, there are many forms of spider silk. A ‘typical’ orb spider for example, will combine at least four types of silk to make a web. Secondly, even for the main type of structural silk (Major ampullate), the statement that it is stronger than steel is sadly pushing it a bit. The issue is that it depends on exactly how you define ‘stronger’ and the species of spider that makes the silk. Spider silk can be comparable to steel in terms of its tensile stress (how much it takes to break it), but it is when it is compared to steel based additionally on the weight of the material that spider silk can be considered ‘stronger‘. When you combine this with the fact that spider silk is more environmentally friendly (and biodegradable) than man-made comparable fibres such as Kevlar, it is clear why research is being done into understanding, and synthesising, spider silk.

A question arises. If it is so strong and so lightweight, why don’t we farm the spiders to harvest the silk? Wouldn’t this be quicker than trying to synthesise it? Clearly we weren’t the first to think this and a farmer in North Carolina, USA, tried in the 1930s. Unsurprisingly, there were issues. Firstly, it took 57000 spiders to produce 0.45 Kg (1 lb) of spider silk. Secondly, if they weren’t kept in (expensive) solitary confinement, they ate each other. It seems that the N. Carolina spider farm was not a commercial success. However, as described in the New Yorker (8th Feb, 1941), a certain Miss Mary Pfeifer did harvest spider silk in the first half of the twentieth century, for use as cross hairs in targets for surveyors and, more sinisterly, bombers. Glass engraving at the time was not fine enough for making the cross hairs. The thinnest line that could be made by a diamond cutter into glass was about double the diameter of the silk from spiders webs and so spider silk had an obvious ‘niche’ market.

HM Ng, spider on web
It takes several types of silk to spin a web. Image © HM Ng

In 1941, Pfeifer would pay “small boys” from the neighbourhood 15 cents for each useable spider that they caught and brought to her. She would then harvest the silk and wind it onto spools ready for use in target sights. Since then we have developed nanofabrication techniques which mean that very thin strands of metal (such as platinum) can be positioned onto the lenses. Continuous strips of metal of around 10 nm thickness (this is one thousandth of the width of a spider silk) can be routinely deposited. Through the development of these and similar manufacturing techniques we no longer need spider silk for use in cross hairs. It is probable that the market cornered by Mary Pfeifer no longer exists.

Spider silk however remains one of many areas where, by studying nature we get clues as to how to overcome various technological challenges. Sometimes devices possibilities are obvious, such as with the opportunity of synthesising material with the strength to mass ratio of spider silk. Sometimes however devices are a long way off. It would be a shame if we prioritised research into devices at the expense of appreciating the ingenuity of nature’s own solutions to its problems. As the story of Mary Pfeifer shows, sometimes today’s obvious devices are not those of tomorrow, who knows where research done purely out of curiosity would lead us.

 

E&J’s Pantry is at 61 Endell Street, WC2H 9AJ

More information about spiders webs can be found in “Spider Silk”, L Brunetta and CL Craig, Yale University Press, 2010