Joule

Conscience Kitchen, Notting Hill

Conscience Kitchen Restaurant and Coffee House on All Saints Road in Notting Hill.

It was 8am on an unseasonably warm morning in November. There were two cafes open on All Saints Road in Notting Hill, but Conscience Kitchen had an open door and comfy looking seating outside. Conscience Kitchen describes itself on its sandwich board as a “restaurant and coffee house”. At 8am in the morning, I wasn’t going to try the restaurant bit (though there were croissants available), but I did enjoy the coffee house bit. Seating had already been arranged outside. There were comfortable and cushioned seats immediately outside the cafe, a set of table and chairs on a converted parking space diagonally in front and a covered section in the parking space immediately outside the cafe. There were also plenty of seats in the spacious interior. The cushioned seats just by the window however offered a perfect spot to watch the world go by.

As it was a week day, plenty of people were either commuting to work or taking children to school. It is interesting how much you can discern about someone passing by when you listen to how their footsteps sound. Confident and clipped, shuffling or lethargic, or occasional combined with the whirling of the wheels of a scooter. A large number of characters passed by as I sat with my coffee. The coffee was an El Salvador single origin roasted by Round Hill coffee roasters. There was also a guest coffee on offer that day from a roaster in Amsterdam but as I didn’t realise this until I was paying I missed the opportunity to try both sorts.

Conscience Kitchen signed the lease on the shop in March 2020. What timing! Shortly after opening they had to close with the lock-downs and so the past eighteen months have been a series of adaptations as they renovated and grew their business. It does seem that their focus on good, organic food has attracted a loyal local following. At times during the second lockdown, the coffee house was turned into a produce store and while those days are far behind us (hopefully), that time did allow the locals to appreciate the care that Conscience Kitchen took over their ingredients. The pandemic times have also affected the seating arrangements with both the aforementioned parking space seating and the outdoor heaters a sign of our times. It was fairly warm that day and so I declined the offer of them turning the heating on for me, I had a hat and a coat after all. But this did give me a reason to look at the heater a bit more closely.

The heater at Conscience Kitchen. You can see the coiled element and the reflecting domed surface.

The heater consisted of a strange light bulb like fitting which led to a coil of what I had assumed was wire, enclosed in a tube and backed by a silvered domed surface. Investigating such heaters later, the ‘wire’ was more likely to be a weaved carbon fibre element. Regardless of what the heating element was made from, the mechanism of heating is the same. The power emitted by the element is the product of the electrical resistance of the element and the square of the current going through it. This relation, known as the Joule-Lenz law was discovered independently by Emil Lenz and James Prescott Joule in the 1840s. So why use weaved carbon fibre as a heating element? There are presumably a few reasons. Firstly, as a weave, a network of fibres, the heater will be more resilient if one of these, for any reason, breaks. If we had a single tungsten wire (as an extreme example), and it broke, the heater would no longer work. This makes the heater more long lasting. But there is a second, more physics based reason for using carbon fibre.

The power rating of the heater is defined as the energy emitted per unit time. When you subject a material to a given amount of energy, it is heated. The increase in temperature of the material is proportional to the amount of energy you put in, divided by the specific heat capacity of the substance which is material dependent. The specific heat capacity of woven carbon fibre is approximately twice that of copper and five times that of tungsten. This means that, for the same amount of energy the carbon fibre will heat up less than the metal wires. This provides the clue for the silvered dome. The heat from the heater is not really just coming directly from the electricity passing through the heating element. The second component is the infrared radiation emitted as a consequence of the temperature of the heating element. As the carbon fibre is not so hot as a metal element of the same power rating, the infrared radiation is at a different wavelength which turns out to be more efficient at keeping us feeling warm. The silvered dome was there to reflect the heat back towards the people on the terrace, further increasing the efficiency of this heater.

Looking further around, I noticed the hashtag on the Conscience Kitchen sandwich board: # Less is way more (unsure about the spacing!). Does this have an analogue in physics? Since the time of Joule and Lenz, physics has undergone increasing specialisation. In Joule’s time, physicists could investigate any number of topics which were also related to each other: heat, optics and electricity, or magnetism and fluid dynamics. Experiments with electricity informed our understanding of thermodynamics for example, while mathematics provided connections between magnetism and fluid dynamics via vortices. Researching one of these fields could, and did, lead to fruitful advances in other fields.

All about the coffee.

Since then, physics has become increasingly specialised and our research focus very narrow. In my field of magnetism, it is highly unlikely that I would get to investigate any aspect of fluid dynamics except for fun over the coffee table. It has been joked that, as individuals at least, we know ‘more and more about less and less’. This specialisation has however led to an enormous growth in our understanding of each of these sub-fields, and, correspondingly, a growth in the technological applications of the research. For example, dedicated research into a specific small detail of how electrical current travelled through layers of magnetic materials led to the sudden increase in the storage capacity of hard disks in the 1990s (and to a Nobel prize). The increased ability to store data has led to other fields being able to investigate highly data intensive areas and so produce advances in their subfields too. These are advances that could not have been made without specialisation.

Is this the ‘more’ of the “less is way more” equivalent for physics? Or is there perhaps a ‘way more’ about it?

The science historian LWH Hull described our situation as if the varying specialists were like people exploring the branches of neighbouring trees, “A man cannot understand other people’s problems by interrupting his own work to climb a few feet up their trees…”* Where then does this leave science? No physicist can any longer be a practitioner of the entire field of physics. Certainly no scientist can any longer understand ‘science’. And yet physics progresses because we work together in an inter-disciplinary way using our community to build a deeper understanding of the whole. This can only work because there is trust in other scientists and in the integrity of the work that they do. A trust that builds community which has consequences for our approach to society. Michael Polanyi took it further “Fairness in discussion has been defined as an attempt at objectivity, ie. a preference for truth even at the expense of losing in force of argument. Nobody can practise this unless he believes that truth exists.”**

“Less is way more”, but how “way more” do we want to take it?

Conscience Kitchen is at 23 All Saints Road, W11 1HE

*Quote from History and Philosophy of Science, LWH Hull, Longmans, Green and Co Ltd, 1959 – it is possible that it is not a verbatim quote as I only have my notes of this book with me at the moment and not the full text.

**In “Science, faith and society” by Michael Polanyi, Oxford University Press, 1946

Making coffee work

Cogs, Wimbledon Common, Windmill, Contact S2b, instant coffee and washing soda developer
Cogs on Wimbledon Common, taken using a film based camera and developed using (instant) coffee. A way to make coffee ‘work’ but not the one linked to Helmholtz.

Search online and you can find videos of machines that lift cogs or turn wheels that are powered by the steam rising off a coffee. You can see an example here and find instructions for how to build your own here (a “stay at home” hobby project perhaps?).

Although such machines are very much for the hobbyist, the principle of the steam engine drove the industrial revolution. And, even now, much of our power network relies on somehow heating water which then drives a turbine that generates electricity. Underlying this is the principle that energy can be transformed from one type to another but is, ultimately, always conserved.

The concept is easiest to visualise with a pendulum or a swing. At its height, the pendulum has a maximum of potential energy but is not moving (so its kinetic energy is zero). As it passes through its minimum height point, the speed of the swing (or pendulum) is maximum and the potential energy at a minimum. Indeed, the amount of potential energy lost by the pendulum is equal* to the amount of kinetic energy gained. The same can be extended to “work” which, in the language of physics is always energy. If a certain amount of energy is put in, a certain amount of work can be produced. In a closed system and without loss, the amount of energy you put in is the amount of energy you get out. In any real system, some of that energy is lost to heat or other methods of loss.

Press Room coffee Twickenham
Whether you make your coffee as a pour over or an espresso, the principle of conservation of energy is always the same. The energy you put in will equal the energy you get out (with some lost as heat as the coffee cools). Pour over at the Press Room, Twickenham.

To use a more coffee related example, in an espresso machine, work is done to put the water under high pressure (and separately to heat it). This pressurised water is then allowed to escape through the coffee puck where the work originally done pressurising it gets transformed into the kinetic energy (speed) of the water going through the group head. Changing the pressure changes the speed at which the water goes through the puck in an analogous way to how changing the height of the pendulum drop affects the speed as it goes through its central point. Of course you won’t always see this because changing things like the grind size in the espresso puck will also affect the route that the water takes as it travels through the puck and so the actual speed at which you see the coffee-infused water leaving the espresso basket will be affected by that too. The real world is never quite so easy as the ideal.

A pour over works in a different way. Here, the energy is stored in the water ‘bath’ in the filter as gravitational potential energy. As the water falls, it gains kinetic energy at the expense of this gravitational energy (or height). As the espresso machine also works with gravity, the conclusion would be that the water will move much faster through the espresso puck than the pour over bed. That this often doesn’t seem to be so is again because of the effects of the resistance of the coffee bed or espresso puck, on the espresso and the pour over.

This concept of the conservation of energy has been engrained into us from an early age. And so it may be surprising that it is a fairly recent principle in physics. For although versions of this principle had been considered for many years, it had not been recognised until the 1840s (by James Joule and Robert Mayer in 1843 and 1842 respectively) that work and heat were interchangeable. And it wasn’t until 1847 that Helmholtz recognised that all energy was conserved. Although at that time he was using the word ‘force’ for what we now call ‘energy’, and what we now call kinetic energy was thought of as a ‘living’ energy. He wrote:

“… the loss in the quantity of potential force is always equal to the gain in living force, and the gain of the first is the loss of the second. Thus, the sum of the existing living and potential forces is always constant.”**

So, among the many contributions to physics that he made, Helmholtz also has a claim to being among those who developed the field of thermodynamics which remains crucial both for physics and for our industrial and technological progress.

Rag&Bone, Rag & bone, coffee Victoria, coffee Westminster
Rag & Bone Coffee in front of St Matthew’s Church. Much of our understanding is based on our assumptions about how the world works. The challenge for us is to identify those assumptions that underlie our thinking.

There is perhaps a cautionary note here for any who are tempted to think that science and religion are always somehow in opposition. For the British scientists who contributed to the development of the idea of conservation of energy (such as Joule and William Thomson (Lord Kelvin)), the concept was founded on the idea of a Creator God: as only God could create or destroy, so it followed that energy of itself, could never be either created nor destroyed, it could only be transformed from one form to another. The idea of a God was, for them, implicit in the idea of the conservation of energy**.

Helmholtz had a philosophical disagreement here. For him, the principle was founded on a Kantian understanding of philosophy***. Certainly certain things had to be assumed at the beginning (such as the principle of causality and the existence of matter outside of our perception of it). But once these assumptions had been made, the principle of conservation of energy followed in a deterministic manner.

Does this matter? In our everyday experience of engines and the way things work, conservation of energy certainly seems to be crucial. We no longer question the principle but assume that one form of energy is transformed into another and is continuously conserved even as it is dissipated into the universe as heat as our coffee cools. But nonetheless, Helmholtz’s understanding was founded on certain assumptions, beliefs, just as Joule and Kelvin’s. It helps to be aware of the philosophical underpinning of our science so as to ensure we don’t have over confidence in what we can, and cannot, know.

So Helmholtz can teach us something else as we gaze into our coffee. Our world is multifaceted, and what we believe about what the world is, influences and informs our understanding of how the world works. Our challenge is to look into ourselves as we sip our coffee and to start to see what we believe we know and what we can actually know. And if we were to really do that, what conflicts would we find?

*With the usual caveats of no energy being lost to friction etc.

**”Helmholtz and the British Scientific Elite: from force conservation to energy conservation”, David Cahan, Notes Rec. R. Soc (2012), 66, 55-68

***”Helmholtz: from enlightenment to neuroscience”, M Meulders, MIT press, 2010

Counting the caloric at Jaz & Jul’s Chocolate House, Chapel Market

Jaz Jules chocolate house

Jaz and Jul’s, The Chocolate House on Chapel Market

The London coffee houses of the seventeenth and eighteenth centuries have entered history as Penny Universities, places of debate and centres of news. Together with the (scientifically based) Grecian, there was Jonathan’s in Exchange Alley (origin of the stock exchange) and Lloyd’s on Tower Street (associated with insurance). But along side these coffee houses there were the chocolate houses, Whites and Ozinda’s on St James’ St and the Cocoa Tree in Pall Mall. White’s in particular developed such a reputation that it features in Hogarth’s The Rake’s Progress (which can be seen at Sir John Soane’s museum).

So it is an interesting bit of history repeating to find Jaz & Jul’s, a chocolate house on Chapel Market. The interior here is very far from Hogarth’s rendering of White’s. Here, light fittings hang from the ceiling like drops of chocolate about to melt into the café while photographs of cocoa plants and farms adorn the walls. Moreover the emphasis on social responsibility, including in sourcing, mean that this establishment is worlds away from the debauched shenanigans at White’s. Their coffee is roasted and supplied by Monmouth while the cakes are hand made and, needless to say, very chocolatey. The light and fluffy chocolate-Pimms cake arrived with my coffee presented on a plate and matching cup that reminded me of a mint-chocolate-chip ice cream.

Interior of Jaz and Jules Chapel Market

The chocolate counter at Jaz and Jul’s

The side of the counter was tiled to resemble a bar of chocolate, which immediately reminded me of the physics and chemistry of chocolate crystallisation. However, the physics connection of this cafe-physics review is a bit more lateral than that. Soon after I had enjoyed my incredibly chocolatey cake at Jaz & Jul’s, a study was released which showed that Britons were significantly under-reporting their daily calorie intake. Could it be that the obesity epidemic is a result of us eating too much rather than merely exercising too little? Apparently, rather than consume the (recommended) levels of 2500 kcal for men and 2000 kcal for women, many people were eating up to 3000 calories per day. Everything in moderation of course and there was plenty of room in my own calorie count for that great piece of cake (honestly). But the word ‘calorie’ turns out to have a connection with chocolate in a more unexpected way.

Calorie comes from the Latin, calor, meaning heat which in turn hints at how we used to think about heat itself. While we now think of heat as energy, which is why it doesn’t even strike us to equate the ‘energy’ in the chocolate cake with the number of kilo-calories in it, this is not how heat was always viewed. In fact, in the eighteenth century, about the time of the old chocolate houses, heat was thought of as a type of fluid, caloric. Caloric was thought to be able to flow in and out of all substances. When something got hot it was because the caloric flowed into it, when something got cold, it was because the caloric had leaked out. Caloric theory was in many ways very successful in understanding heat and heat processes. For example, the theory easily explained thermal expansion, if a fluid had to flow into something in order for that thing to warm up, then surely, the fluid has to occupy some space, the object must expand to hold it!

Mint choc chip cutlery

Coffee with the Chocolate-Pimms cake.

One area that was tricky for caloric theory though was the fact that friction could cause something to heat up. Such heat generation is crucial for our extraction of chocolate. Once harvested from the plant and cleaned, the cocoa bean is first roasted then shelled to leave the cocoa ‘nibs’. These nibs are then ground more finely. As they are being ground, the friction caused by grinding is enough to cause sufficient heat to melt the cocoa butter in the nibs which is then extracted and retained for later use*. How could you explain this heating if you thought of heat as a fluid? The traditional explanation was that as the two objects rubbed against each other (in this case, nib and stone grinder), the caloric fluid would be squeezed out, it would appear as if heat had been generated.

Benjamin Thompson, Count Rumford (1753-1814), disagreed with this explanation of heat. In the course of a colourful career he had been involved in manufacturing cannons in Bavaria. Rumford had noticed that a lot of heat was generated each time a cannon shaft was bored out. The heat produced continued as long as the grinding continued. If the heat were due to the cannon leaking caloric, surely there would be a point at which the cannon stopped getting any hotter. Yet this did not happen. Rumford suggested (correctly) that instead what was happening was that the energy generated by the boring was being transferred into the metal of the cannon, causing microscopic motion.

Although the heat as motion/energy idea eventually caught on, caloric in some ways still survives in the name that we give to our food energy intake. And so we can return to the cake, could it be that spending time thinking about the caloric in the cake can justify the calories consumed eating it? Sadly the jury is out on whether thinking counts as calorie counting exercise. It seems that the brain’s energy consumption is already so great (at 20% of our resting metabolic rate), that intense thinking does not add too much to the energy consumed by the brain. So we’ll need another excuse and I don’t think we have to look far. The coffee and chocolate at Jaz & Jul’s is delicious enough to justify a significant chunk of your daily calorie count, just based on considerations of taste. Everything in moderation!

 

Jaz and Jul’s is at 1 Chapel Market, N1 9EZ

*”Chocolate: A Global History”, by Sarah Moss and Alexander Badenoch, published by Reaktion Books, 2009