Kings Cross

Hidden appearances at HoM

hot chocolate, soya, marsh mallow, HoM

Hot chocolate with marshmallows at HOM, Kings Cross.

In these long dark afternoons in the northern hemisphere, what could be better than a warming mug of lovely coffee in a bright environment? And so it was that we ended up at House of Morocco (HoM) on the Caledonian Road. Alerted by Brian’s Coffee Spot that Pattern Coffee had changed hands and become HoM we headed up to Kings Cross one damp afternoon in December to see how things had changed. Entering HoM is a strange mix of déjà-vu mixed with new. The pattern on the wall next to the window remains, as does the layout of the place. However it is also clear that much has changed since HoM took over.

There are murals and variously coloured cushions dotted around the café. Even in the darkness of the afternoon, the café was bright, but also crowded. We ordered a soya hot chocolate, a long black and a cheesecake and found a seat perched at a small table for two near the door (the only seat left at the time). The coffee, roasted by Terrone Coffee, was nicely balanced for the afternoon. But it seems that the hot chocolate and cheesecake combination were a real hit. The cheesecake was apparently very good (definitely worth a return visit apparently) while the hot chocolate went very quickly!

Inside the café, the windows were steaming up with the warmth of the inside. We over-heard that this was because of the coffee machine rather than any extra heating that had been installed. Does this suggest an alternative energy source? Coffee machine heaters to go with treadmill electricity generators in gyms?

all about pigmentation at HOM

Menu with sugar bowl and glazed tile at HOM, Kings Cross.

Meanwhile, the decoration was demanding my attention. A vividly coloured glazed tile supported a jar of sugar which was propping up a black and white menu. The menu had an illustration reminiscent of henna tattoos while above all of this balanced a peacock feather in a vase. Underneath the peacock feather was a poster advertising the “Phantom of the Opera”. The whole ensemble was suggestive of appearances and how they can be deceptive. The phantom of course wore a mask to disguise his disfigured face. But the peacock? The peacock is hiding something too.

Many of the colours that we see around us such as those making our coffee brown and making the tiles colourful are as a result of energy from the light being absorbed by the atoms in the substance (the coffee or the tile). This type of light absorption (and emission) can be connected with vortices in coffee as was discussed here. However the blues and greens in a peacock feather are different. If you look at the feather under a high powered microscope, you will find that the feathers are not dyed as such, in fact the natural colour of the feathers is quite dull. Made from keratin (as you can find in your fingernails) and melanin (responsible for the brown pigmentation of your skin, eyes and hair), the feathers do not seem blue at all. In fact it is the structure in the feather that is producing the colour rather than any dye that produces the colouration.

It turns out that there is a long history concerning our understanding of the colours of a peacock’s feather. It started with Robert Hooke who, in 1665 described the feathers of both peacocks and ducks and noticed that the colours he saw under an optical microscope were ‘destroyed’ by putting a drop of water on the feather. A little bit later and Isaac Newton was suggesting that the colouration was due to the thickness of the transparent bits of the feather. There’s a link here to coffee. Newton was suggesting that an effect similar to thin film interference (which causes the rainbow colours on the bubbles in a coffee) was causing the colours of the peacock feather.

appearances at HoM

Peacock feather and phantom poster with the top of a mirror. How does structure affect what is seen?

As our understanding developed through the centuries (and the microscopes became more powerful), it became apparent that while thin film interference (and multiple film interference) could cause some animals to appear as if they had certain colours, the peacock, along with some other animals, was a little bit more special. Rather than just being the result of reflection off an interface, the peacock’s feathers showed structure at the nanoscale (1/1000000 of a mm). The keratin and melanin in the feathers were arranged in a square lattice to form what is known as a ‘photonic’ crystal. The way this structure reacted with incoming light meant that only certain wavelengths were reflected from it. Depending on the size of the layering in the feathers, they appeared as blue, green or yellow.

Although a lot more is now understood about the factors, structural and chemical, that lead to colouration in all sorts of creature, be they butterflies or beetles, peacocks or pigeons, there is still more to discover, more to understand. The authors of the paper referenced here wrote

“In this paper, we describe a wide variety of structural colors occurring in nature and attempt to clarify their underlying physics, although many of them are not fully clarified.”

There’s clearly a lot more work to do before we can properly explain these “beautiful microstructures”.  And plenty of time to do so as we sit enjoying well made coffee and hot chocolate in a bright and warming café.

HOM can be found at 82 Caledonian Road, N1 9DN


Constructive interference at Frequency, Kings Cross

exterior of Frequency Kings Cross

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

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

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

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

mug of coffee at Frequency

Coffee at Frequency.

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

They mean noise.

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

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

transmission lines, electrical noise

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

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

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

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

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


Ripples in the Knowledge Quarter at Pattern, Kings Cross

Pattern, coffee, Kings Cross, Kings X

Pattern Coffee, Kings Cross

In 2018, the Institute of Physics will move to Kings Cross and into what is being called the “Knowledge Quarter”, an area incorporating the British Library, the newly opened Francis Crick Institute and the University of the Arts, among others. Coffee houses have, in the past, been integral to the development of knowledge, places where scientists, artists and the generally interested would meet to discuss new ideas or groundbreaking results. So what about the cafés in Kings Cross? Where will tomorrow’s scientists, artists and the generally interested meet?

Knowing that I would be in the Kings Cross area a couple of weeks ago, I looked up the Kings Cross coffee guide by doubleskinnymacchiato and decided, for not-quite-random reasons, to try Pattern on this occasion. I had been forewarned that the first thing that I would notice would be the colourful patterns on the wall. A good call, that was indeed one of the first things you notice as you walk in. Secondly though were the hat-lampshades on the bulbs over the table at the window (visible in the photo on doubleskinnymacchiato’s review). As anyone who has met me in autumn/winter may appreciate, the lampshades immediately made me feel right at home. It was fairly crowded when I arrived in the late-morning and so I shared the bench in the window with a couple of people who seemed to be discussing history/philosophy and how to write properly referenced argumentative essays. The Americano I had ordered was brought over and, slightly self-conscious to photograph it while sharing the table, I just had to enjoy and savour the well made coffee. There is, perhaps, almost too much to notice at Pattern. But something behind me caught my eye, something that connects coffee, patterns and this café: An old style dial telephone, fixed to the counter.

telephone, dial, coffee Kings X

Patterns in the cord, patterns in the telephone. An unusual feature at Pattern, Kings Cross.

Although the history of the invention of the telephone is quite controversial, the bit that reminds me of coffee is not so contentious, it is to do with how the telephone works. Let me explain.

In the gallery the “Information Age” at the Science Museum in London, it is argued that the commercial success of the telephone was driven by the invention of the carbon microphone, simultaneously invented by David Hughes (1831-1900) and Thomas Edison (1847-1931). It is the Edison version that prompts me to think of espresso. Edison’s microphone worked by packing a cylinder of carbon granules between two metal plates. In my mind I think of Edison’s carbon microphone as similar to a perfectly tamped coffee block in a filter basket. In the microphone, one plate was fixed, the other was flexible and acted as a diaphragm. When somebody spoke into the microphone, the diaphragm would vibrate causing the carbon granules to move alternatively closer together and further apart. Carbon conducts electricity and so the resistance of the microphone changed if the carbon granules were closer together or further apart. The sound waves impacting on the diaphragm were being perfectly translated to electric current patterns that could be transmitted through the telephone lines. The packing of the carbon granules would need to be optimum to transmit the sound, just as the pressure used to press the espresso tablet needs to be just right, enough contact between coffee grains to prevent the water flowing straight through without producing a good coffee, but not so much that the water cannot percolate through the coffee tablet and what should be a lovely espresso becomes over extracted. The ground coffee pressed into the filter basket at Pattern must have fitted this optimum density very well. A well poured espresso revealing that they had achieved that optimum balance between compression and space in the espresso tablet. Good coffee, interesting physics, I’m sure the Institute of Physics will be pleased when it eventually moves to its new home with such great coffee neighbours.

IoP poster in Kings Cross

Physics is everywhere! (But coming to Kings Cross)

Although slightly off topic, a cafe-review considering telephones would not be complete without including the story about Erasmus Darwin, the Devil and his “speaking machine”. Erasmus Darwin (1731-1802) was a fairly portly man who worked hard. So it was inconvenient for him to have to go from his study to the kitchen when he wanted something to eat. Being a bit of an inventor, he installed a speaking tube in his home that connected his study to his kitchen. Desmond King-Hele in “Erasmus Darwin, A life of unequalled achievement”* described what happened next:

One day a local yokel who had arrived with a message for Darwin, was left alone in the kitchen. He was terrified when a sepulchral and authoritative voice from nowhere demanded ‘I want some coals’. Such a request could only come from the Devil, he thought, wishing to stoke up hell’s fires. The man fled and would not come near the house again.

The poor local may have been bewildered by the number of telephones and ‘voices from nowhere’ that surround us now. If you’re reading this in a café, why not look around you, notice some strange connection (the very lateral ones can be particularly fun to ponder), and then let me know what you have seen. It’s always interesting to hear the science, history and connections that people notice as they sit in cafés around.

Pattern Coffee is at 82 Caledonian Road, N1 9DN

*Desmond King-Hele, “Erasmus Darwin, A life of unequalled achievement” was published by Giles de la Mare Publishers, 1999.