tea bags

Time for tea?

Matcha, tea in Japan, frothy tea
A Matcha tea in Japan. A lot to contemplate here.

A recent article in Caffeine magazine caught my attention. Emilie Holmes of Good and Proper Tea was writing about the joys of appreciating loose leaf tea. While tea is a little diversion from coffee, January is traditionally a time to look forward as well as back and maybe, BeanThinking should occasionally cross over to the tea side. It was one line in particular of that article that puzzled me. Writing about the ‘naturally “slow” nature of the tea ritual’, Holmes observed that while brewing loose leaf tea you would be able to see “the leaves in a glass pot emit wisps of colour as they infuse…”

It was great to read someone who clearly had spent time carefully observing their tea. And yet that sentence prompted a series of questions in my mind. It was not that I doubted the observation, indeed, thinking back to teas I have made and enjoyed, I realise that I have seen these wisps before. It was more a question of why would it happen, why would the brewing tea emit lines of colour from the leaves? These lines must be telling us something.

diffusion, convection, tea brewing
A tea bag in hot water. The lines of tea are difficult to see in the photo, you’ll just have to do your own experiments, but, streaming from the bottom of the bag, you can see wisps of darker tea-water.

We need to think about how tea brews. A first mechanism would be through turbulence. Hot water poured onto a bed of tea leaves would stir them up and the resulting movement within the pot would mix the leaves with the water leading to a properly brewed cup of tea. This is very much the lazy tea brewers bag-and-cup method (which I can share). It would lead to a brewed tea, but it could not lead to a situation in which you could sit back and see wisps of colour. That requires calm and the quiet moments of a pot of tea brewing while you can enjoy the process.

A second mechanism would be through diffusion. Ultimately the same mechanism as the principle behind how LEDs work, diffusion is where the soluble parts of the tea leaves would travel, through the process of a random walk, throughout the water of the pot. This is a very slow process and we would expect that the concentration of colour would be most intense around the leaves and then fade out gradually with distance from the leaves. We would not expect ‘wisps’ nor lines of tea, that suggests something else.

It suggests the third mechanism of the tea brewing: a mix of diffusion and then convection within the hot water of the pot. The lines of tea are indicating that within the cup, regions of the hot water are at slightly different temperatures. Owing to the hot water being in contact with cooler air surrounding it, the surface of the water is cooling down and sinking, leading to a convective motion within the water inside. As the water moves it carries the diffused tea with it into new areas of the water, a movement of hot water to cooler water and back again. The tea is carried in a line because the convection patterns are occurring in small cells within the tea pot, small regions where hot tea is moving towards cooler tea which is warmed and itself moves. The convection does not happen as if the hot water is one big mass but a series of smaller ‘cells’. We see similar cells on the surface of the Sun. The lines are telling us of the movement in the tea pot and the amount and speed of their movement reveals more about how hot the water is relative to the air outside the pot.

diffusion only
A tea bag in cold water: This time, there are no wisps of tea as the drink brews. Instead, there is a slow diffusion of tea infused water from the bag outwards.

Testing this idea I required tea bags. My tea pots are opaque and so would not help me to appreciate this detail of brewing a cup of tea and so it was back to the bag-in-cup method. However, in order to avoid turbulence, I poured the water (hot or cool) into the mug before adding the tea bag. It was not the best way to make a tea, apologies to tea lovers, but it was a tea that I do not enjoy anyway, so it was good to use it up. Sure enough, when the tea bag was put into the hot water, within a very short time, wisps of coloured water formed lines curling underneath the bag. Why did they flow down? Was it because the tea in the bag was slightly cooler than the hot water and so, as the tea diffused out of the leaves it moved with convection downwards because of gravity and the fact that cooler water is denser? A tea bag in cool water however behaved differently. The water in the cup had been taken from the tap and then left in the cup for a couple of hours so that the water was definitely at the same temperature as the room. This time, the tea bag first floated and then sank to the bottom of the cup. There was no obvious infusion of the tea-coloured water into the plain water but slowly the region around the bottom of the tea cup at the bag turned browner with the tea. As time went on, this region expanded to give a tea layer and a water layer.

The wispy lines of tea only happened when using hot water. Which suggests a further experiment. How do these wisps change when brewing for black teas as opposed to green teas (which use a lower brewing water temperature)?

After about five minutes the tea brewed in hot water (left) was fairly evenly distributed throughout the cup whereas the tea brewed in cold water (right) showed a distinct layering between concentrated tea at the bottom of the cup and plain water above that layer.

One last observation with these tea bags in the hot water. Some of the tea floated within the bag, some sank, as time went on, more tea leaves fell towards the bottom of the bag (which was itself floating). What was happening there? Maybe if you experiment with your tea, you can let me know in the comments below, on Twitter or on Facebook. There are definite advantages to slowing down and brewing a proper cup of tea.

Plastic free coffee?

a take away cup

There’s plenty of plastic in coffee & it’s not just in the obvious take-away cups.

So we’ve probably all done it, walked into a coffee shop and purchased a take-away coffee while in a rush to get elsewhere. It’s the moment that our desired commitment to environmentally responsible behaviour clashes with our (briefly stronger) desire for sustenance on the move. Using a keep-cup (or similar) would avoid this bit of single-use plastic but even so, is this the only plastic that you encounter when you enjoy a coffee? Actually, once you start to notice it, you will find single-use plastic in a number of surprising places.

An initiative called “Plastic Free July” aims to raise awareness of the pervasiveness of single-use plastic as well as to challenge us to do something about it. So, partly as an educational exercise, I signed up to the Plastic Free July, not because plastic is always bad, (there are arguably some very good, even environmental, reasons to use plastic, see below) but because plastic is a substance that takes a long time to break down once discarded and we use it so often even without thinking. So, before revealing just how easy – or hard – it has been to eliminate single use plastic from everyday life for the past couple of weeks, it’s worth taking a look at the problems, benefits and occurrence of plastic in our lives. Particularly while we are enjoying a tea or coffee.

Some definitions

Plastic comes in many forms and Plastic Free July does not aim to avoid all of them. It is single use plastic that is the concern: Bits of plastic wrapping, plastic bags, aroma valves. Things that are used once and then discarded. Can you avoid using these, even for one week or even just one day? Why not sign up and commit yourself to trying to find out.

Plastic Problems

Earth from space, South America, coffee

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

Two of the major issues with our use of plastics are the problems of littering and that of degradability, particularly when that litter finds its way into the oceans. Between 60-80% of marine litter is plastic. It can cause the deaths of marine life not just through its being eaten (thereby causing internal injury or malnutrition), but also by entangling sea creatures and so causing death through drowning or other injury. Moreover, the bits of plastic that float around our oceans can provide a home to various micro-organisms transporting them around the world to areas of the planet that they would not ordinarily have been able to reach.

Nor is it just a problem for the oceans. Plastic takes many centuries to decompose and although there are plastics that decompose more quickly (oxo-biodegradable and compostable, more details below), clearly there is a need to reduce the amount of plastic we throw away. A further problem with plastics is that their manufacture requires the use of a limited resource. 4-5% of global petroleum production is used for the manufacture of plastic∗. But nor is it just petroleum products, the thing that makes carrier bags opaque is an additive called TiO2. It is therefore somewhat sobering to realise that 25% of the plastics manufactured in the US are used in packaging* and 37% of the plastics produced are for disposable items. Clearly we have room to live less wastefully here.

Why it’s not all bad

paper bag roasted coffee

Is it better to swap to paper packaging? It may depend on what problem you’re trying to solve.

Although there is a big problem with plastic waste, a different environmental problem has arguably benefited from our use of plastic packaging: The greenhouse effect. Consider the way that ground coffee is often sold in a supermarket. Frequently the coffee comes in metallised plastic packaging complete with plastic air-valve (or aroma valve). Alternatively, coffee can be packaged in a steel can (as used by a well known coffee roasting blend). Steel is 100% recyclable and so is good for the degradability/litter problem. However it is heavy and cylindrical. This means that to transport an equivalent amount of coffee in steel cans costs more, both in terms of economic and environmental costs, than the lighter, less bulky plastic of the alternative*.

What about paper packaging? It is interesting that even here, the situation is not clear-cut. A study concerning the greenhouse gas emissions involved with the manufacture and transportation of different sorts of shopping bag had what may be a surprising conclusion. In order to achieve a lower CO2 footprint than a standard plastic shopping bag re-used once as a bin-liner, a paper shopping bag would have to be re-used 4x while a cloth bag would have to be re-used a staggering 173x. You may well argue (as I have) that it is still better, environmentally, to buy your coffee in paper packaging, but if thinking purely in terms of the CO2 emissions, you may want to try to find a way to re-use the coffee bag a few times.

Lastly, the litter and degradation problem need not be insurmountable. In recent years, various manufacturers have sought to make plastic degrade more rapidly than ordinary plastic. Oxo-biodegradable plastic has additives in it that, when exposed to UV light, eg. from the Sun, help the (otherwise perfectly ordinary) plastic to completely biodegrade. The process takes a controllable amount of time that can even be as little as 2 years. Compostable plastic too is being developed but there should be caveats on the name. “Compostable” is defined as “industrially compostable” (meaning it degrades if held at a steady 58C), it does not necessarily mean that it composts in your compost heap.

There’s plastic in my coffee?

air valve, plastic, environmental coffee packaging

Aroma valves: are they worth the environmental cost?

So, we’re aware of the problem and want to do something about it but how much is single use plastic really a problem for coffee (or tea) drinkers? Take-away cups are the obvious source of single-use plastic, but plastic can be found in many places as we enjoy our brew. If we are having coffee in a café (even if it is not take out), how about the spoon for the sugar, plates for the cakes or even wrapping around the chocolate bars? If you drink your coffee with milk (cow, soy or almond) it will often come in plastic bottles, yes these could be recycled but would it be better if they were made from something else? (It is an interesting fact that more plastic was sent for recycling in the UK than was used by consumers†).

An easy way of reducing your plastic use would be to use your own mug as a take-away cup (keep-cups for example are designed to be of the correct size for the cafe industry). And there may even be other advantages to you in bringing along your own cup: For Danny S Parker, taking along his own cup for his coffee allows him to better enjoy the coffee, as he says “If you choose a wide mouth cup… the involvement of the nose in the taste on the tongue will accentuate flavour and enjoyment.” Reducing your plastic consumption could mean that even a take-away coffee can provide a moment to enjoy your brew.

What about if you only ever drank coffee at home? Where’s the plastic there? Well, how do you buy your coffee? Do you buy from a coffee roaster that insists on using bags with ‘aroma valves’? These valves cannot be recycled currently and so inevitably contribute to plastic waste. Is this packaging really necessary for the way that you buy your coffee? (See here for an interesting taste comparison of coffee stored in bags with/without aroma valves). Meanwhile, the coffee itself is frequently supplied in a metallised plastic packaging, does the roaster you buy from try to minimise the environmental cost by using recycled/oxo-bio/compostable/paper packaging? Why not ask them?

And tea drinkers, you do not get away with it! There’s plastic involved in tea drinking too. Tea bags are often supplied in cardboard packaging that is then wrapped in plastic, and even loose leaf tea can come in paper bags with plastic windows or metallised plastic bags. Worryingly, even tea bags themselves can occasionally be made of a plastic material that does not break down in a composting bin‡. Plastic truly gets everywhere.

An honest appraisal of how my plastic free July has gone so far

San Sebastian via Aeropress

Giving up plastic can mean taking the opportunity to enjoy your coffee properly.

So, nearly halfway through July and my attempts at being “plastic-free” are mixed. Some things are relatively easy to change, a metal tea strainer and loose leaf tea replaced the tea bags when they ran out. The coffee I use at home comes in paper packaging from Roasting House. Other things such as bottles of shampoo could be replaced by shampoo bars (like a bar of soap only for shampoo). Even the soy milk I use at home was easily exchanged for a home-made oat-milk.

However, some things have been difficult. Shopping particularly is not very plastic-free friendly. Although there is advice on taking containers with you in order to buy meat, fish or cheese from the counter in a plastic-free way, I am not sure that this would work in my local supermarket and anyway, they have to weigh the meat/fish/cheese which will involve them putting it on a plastic bag on the scales. Just because I do not walk away with plastic in my hand does not mean that I am not responsible for its use. Cooking oil too frequently comes in plastic bottles and, given the increased weight and therefore transportation costs involved in glass packaging, perhaps this is an example of a good use of plastic. An attempt to move away from aluminium-lined, plastic tube toothpaste to plastic-free tooth tabs has been complicated by the fact that the tooth-tabs are supplied in a plastic bottle. And I’m afraid that I am partial to a bottle of beer occasionally even though they do have plastic lined metal caps.

So, my plastic-free July has been a bit mixed but certainly not single use plastic free (so far). But, it has been worth it in order to really see just how ubiquitous single-use plastic is in our day to day living. Is it possible for you to cut down just a little bit on the plastic that you use every day? Why not sign up to Plastic Free July and see where your challenges lie.

If you are already signed up to Plastic Free July or if you are trying to live in a plastic-reducing way generally I’d love to hear how it’s going. Also if you have an opinion on the use of plastic in the coffee industry (either in cafes or by roasters) do let me know.

*Plastics and the Environment, AL Andrady (Ed), Wiley-Interscience, 2003

† The study was done in 2006.

‡ I was alerted to this initially by a friend’s comment that certain pyramid-type tea bags never seemed to break down on their compost heap.