THE VACUUM POT
The vacuum coffee pot, also now known as the syphon brewer, is a very old and exceedingly entertaining way to make coffee. It is, however, also extremely annoying in many respects and sufficiently frustrating that many people relegate their brewer to a cupboard or a shelf as a display piece.
Vacuum coffee pots first appeared in Germany in the 1830s. A patent was issued for one in 1838 to a French woman, Jeanne Richard. The design has not really changed a great deal since its conception. The brewer has two chambers, the lower of which is filled with water and heated to boiling point. The upper chamber, which contains the coffee grounds, is then placed on top, creating a seal and allowing steam to build up in the lower chamber. This trapped steam pushes the water from the bottom chamber up through a tube and a filter into the upper chamber. The water is, at this point, just below boiling point and suitable for making coffee. The brew is left to steep for the desired amount of time; it is important to keep heating the lower chamber while the coffee steeps.
To finish the brew, the vacuum pot is removed from the heat source. As the steam cools, it condenses back into water and creates a vacuum, which sucks the coffee from the upper chamber back through the filter into the bottom chamber. The grounds remain trapped and separate in the upper section and the coffee can be poured from the bottom carafe. The whole process is a pleasing application of physics, and is often likened to a classroom experiment. Unfortunately, it is sufficiently difficult to get right that most people try a couple of times and then give up, which is a shame.
Vacuum coffee pots are an elaborate way to make coffee by immersion. Steam rises from the lower chamber and steeps the coffee grounds held above, then condenses the brew into the lower carafe.
ADDITIONAL TOOLS
An independent heat source is required for this brewing method. Some vacuum coffee pots are designed to sit directly on a kitchen stove, others come with their own alcohol-burning candle. These candles are best replaced with a very small, butane camping stove. In Japan and in some specialist coffee shops, the preferred heat source is a halogen lamp placed under the brewer. This is not the most efficient source of heat but it does look fantastic.
Some people use small bamboo paddles to stir the coffee but these do nothing special and a spoon works equally well. While I cannot deny there is pleasure in acquiring and using a special set of tools for a ritual, I won’t claim they make any difference to the coffee.
THE FILTER
Most traditional vacuum pots use a cloth filter, which is wrapped around a metal disc. It is important to keep this cloth clean. After every use, clean the cloth as thoroughly as possible under a hot tap. If it is not going to be used for a few days, clean it with a suitable detergent. For more information about cleaning and storing cloth filters, see (Different Kinds of Filters). There are alternatives to cloth, such as paper or metal, but these often need special adapters.
THE VACUUM POT METHOD
Ratio: 75g/l. Some people prefer to use a little more coffee than this for syphon brewing, especially in Japan where this method is commonly used.
Grind: Medium/caster sugar. Because this is an immersion method, you can match your brew time to the grind size. I would caution against going too fine as you can stall the draw-down process to end the brewing. A very coarse grind will mean a very long brew time at higher temperatures, which can make the brew rather bitter (see Grind Size).
1 Grind the coffee just before you start brewing. Be sure to weigh the coffee first.
2 Boil a kettle of fresh water with a low mineral content, suitable for brewing coffee.
3 Fit the filter into the upper chamber, making sure it is completely flush.
4 Place the bottom chamber on your digital scales and pour in your calculated amount of hot water, following your desired ratio.
5 Transfer the lower chamber to your heat source (a small butane burner, an alcohol burner or a halogen lamp, as shown here) using the handle to move it.
6 Place the upper chamber on top, but do not seal it yet. If you put the seal on too soon, the expanding gases will push the water up into the top chamber before it is the right temperature, making your coffee taste bad.
7 When the water starts to boil, seal the top chamber on top of the lower chamber. If you are using a controllable heat source, reduce the heat to low at this point. The boiling water will now start pushing up into the top chamber. Look directly down on the filter to make sure it is centred: if it isn’t, you will see lots of bubbles flowing from one side. Use your paddle or a spoon to push the filter carefully into place so it is correctly positioned.
8 Initially the bubbling in the top chamber will be quite aggressive, with large bubbles. Once the bubbles become smaller, you are ready to brew. Add the coffee to the water and stir it in until it is all completely wet, then start a timer. A
9 A crust will form on top. After thirty seconds, give it a gentle stir to knock the floating coffee back into the brew. B
10 After another thirty seconds, turn off the heat source. Once the coffee begins to be drawn down into the lower chamber, stir it gently once clockwise and then once anticlockwise to prevent it sticking to the walls of the brewer, but if you stir too much you will get a large dome of coffee at the end of the brew, which suggests uneven extraction.
11 Allow the coffee to draw down completely. A slightly domed bed of grounds will be left in the top chamber. Pour the coffee into a coffee pot, as the retained heat from the carafe can give the coffee a cooked taste. C
12 Let the coffee cool. This brewing method produces an incredibly hot cup of coffee. D
Coffee was first discovered in ninth-century Ethiopia, and the Tomoca coffee shop in Addis Ababa is the oldest surviving café in the country. The later influence of Italian rule is seen in the sleek espresso machines.
ESPRESSO
Over the last fifty years, espresso has come to be considered by many to be the ‘best’ way to drink coffee. This is not true, since no brew method can be inherently better than any others, but espresso is now the most popular coffee drink consumed out of the home, and many cafés charge more for an espresso than for a filter coffee.
Undeniably espresso has been the driver of coffee retail, whether it is part of the Italian-style coffee culture now widely popular, or the Americanized, fast-food version we see in chain coffee shops across the globe.
Making espresso is both incredibly frustrating and also very rewarding. I must offer a word of caution here: don’t invest in an espresso machine at home unless you want a new hobby. The fantasy of whipping up a couple of delicious cappuccinos to drink on a lazy Sunday morning while reading the paper is a very long way away from the work involved in preparing the drinks (and cleaning up afterwards). If you just want the drinks and not the work, then do what I do and pop out to a local café where someone else can deal with it all. However, I accept that, for many of us, great coffee is not available locally and this is a good reason to master the art of espresso brewing at home.
THE INVENTION OF ESPRESSO
As we have already seen, when you brew coffee, the grind size is very important. The finer you grind the beans, the easier it will be to extract the coffee, and the less water you require to do so. This means you can produce a stronger cup of coffee. The problem starts when you try to grind the beans so fine that gravity alone cannot push the water through the bed of coffee. This puts a limit on how strong a cup of coffee you can produce.
This problem has been recognized for a very long time, and the first solution used the pressure of trapped steam to push water through the coffee. Initially this early espresso machine was simply used by cafés to make regular strength coffee much quicker, hence the name. However, the pressure you can generate from steam alone, without endangering lives, is actually relatively low so various other methods such as air pressure or mains water pressure were tried.
The big breakthrough came with Achille Gaggia’s invention. This used a large lever, pulled by the operator, to compress a
spring. When the spring was released, the pressure forced the very hot water through the coffee. The sudden jump in pressure was dramatic, and allowed the use of a much finer grind of coffee to produce a much smaller, stronger, but well extracted cup.
CREMA
For most coffee drinkers, one of the key features of espresso is not just the strength of the cup but also the layer of dense foam that tops the drink. Crema is simply Italian for cream and it is the natural head of foam that forms on top of the coffee, much like a head appears on a pint of beer.
The reason this happens is that when water is under very high pressure it is able to dissolve more carbon dioxide, the gas present in coffee that was produced during the roasting process. When the brewed liquid gets back to normal atmospheric pressure on its way to the cup, the liquid can no longer hold on to all of the gas so it comes out of solution as innumerable tiny bubbles. These bubbles become trapped in the coffee liquid and appear as a stable foam.
For a long time crema was considered important, but in fact it can only tell you two things. Firstly, whether the coffee is relatively fresh – the longer ago it was roasted, the less carbon dioxide it will contain so the less foam it will produce. And secondly, whether the cup of espresso is strong or weak. The darker in colour the foam, the stronger the liquid will be. This is because crema is just a foam of the liquid, lighter in colour because of the way the bubbles refract light, so the colour of the coffee determines the colour of the crema. For this reason, coffee that has been roasted darker will also produce a darker crema. The crema cannot tell you if the raw coffee is good, or has been well roasted, or if the equipment used to make the espresso is clean – all key factors in a delicious cup of coffee.
Patented in 1905, this La Pavoni two-group Ideale model was the first machine of its kind to be marketed. It introduced espresso-style coffee to Europe and, later, to the rest of the world.
THE BASIC TECHNIQUE
To brew espresso, the ground coffee is placed in a small metal basket held in a handle. The basket has tiny holes that allow the liquid to pass through but prevent any of the pieces of ground coffee, with the exception of the tiniest particles, from making it into the cup.
The coffee in the basket is compressed (tamped) so it is flat. The handle containing the coffee is locked into the espresso machine and the pump then activated. The machine pumps near-boiling water from the reservoir in the machine through the coffee; the liquid then drips into the waiting cup below. With some machines the operator decides when to switch off the pump to finish brewing, either gauging the end of the brew by eye or by weighing the coffee as it comes out to make sure the desired amount of water has been used. Other machines dispense a specific amount of water and then stop automatically.
Great espresso is about recipe, and good coffee roasters will supply you with plenty of information about how to brew their coffee to get great results. A good recipe is about accurate measurements and should include the following:
• The weight of ground coffee to use in grams (g).
• The amount of liquid you should produce from that coffee, ideally expressed in grams or at least expressed in volume (ml).
• How long the brewing process should take.
• How hot the water should be for brewing.
Rather than just give a basic guide, I want to offer some information that will help produce genuinely excellent espresso at home, techniques that I have taught to baristas around the world for years and that I believe are key to brewing espresso as well as is currently possible.
A great barista produces the desired amount of coffee in a certain time frame. Even when using a machine as sleek as this 1956 La San Marco, the first thing to check is that the grind of coffee is right.
PRESSURE AND RESISTANCE
The aim when brewing an espresso is to have the machine produce a desired amount of liquid in a certain time frame. For example, the recipe might state that we want to brew 18g of ground coffee and produce around 36g of liquid in 27–29 seconds. In order to achieve this, what we need to control is how quickly the water flows through the ground coffee.
The speed at which the water flows through the coffee determines how much flavour is extracted. If the water passes through too slowly, we take too much out of the coffee and it will be overextracted with a bitter, ashy and very harsh taste. If the water flows through too quickly, we don’t extract enough from the coffee and it will taste very sour, astringent and weak.
The way we control the flow of water through coffee is by changing how easy it is for the water to pass through. This can be achieved by varying two factors: the amount of coffee we use (the more you put in the basket, the longer it takes for the water to pass through), and the size of the coffee particles.
The finer we grind the coffee, the better the pieces fit together and the more difficult it is for the water to pass between them. If you took two jars and filled one with sand and one with the same weight of pebbles, water would flow through the pebbles much faster than through the sand. In the same way, the coarser we grind coffee the faster the machine can push the water through it.
The problem many people experience, and one that brings frustration to thousands of baristas around the world every day, is that when the flow rate is wrong and the coffee doesn’t taste good, it is not immediately obvious if the grind was incorrect or if the coffee dose was wrong. For this reason, in the home environment, I recommend measuring the coffee wherever possible. It will reduce mistakes, frustration and waste. If you have used the correct weight of coffee, you will know that it is the grind size that needs to be changed.
Espresso is probably the most intolerant method of preparation of any food or drink in the world. This is not an understatement. A few seconds outside of the target brew time, a gram of ground coffee too little in the basket, a few grams too little liquid in the cup – all of these will have a dramatic effect on the taste of the coffee and may be the difference between a delightful cup and pouring the results of your hard work down the sink.
My recommendation is to keep as many things as possible constant, and only alter one variable at a time. If you get a disappointing cup of coffee, try altering the grind size first, because if this is wrong, trying to fix something else won’t deliver the results you want, either.
TAMPING
Tamping is the term used for the compression of the ground coffee before brewing. We do this because ground coffee is fluffy, and if we put uncompressed coffee into the machine the high-pressure water would find the air pockets between the coffee grounds and pass through quickly, skipping much of the coffee. When water does not pass evenly through the coffee we call it channelling. When this happens, the resulting espresso will taste very sour and unpleasant, because the water has not evenly extracted the ground coffee.
Many people place a great deal of importance on tamping, but I do not believe it is as important as people think. The goal is simply to push the air out of the coffee bed and to make sure the bed is level and even before brewing. How hard you compress the coffee doesn’t make an enormous difference to how quickly the water passes through it. Once you push all the air out, there is little or no reward for pushing any harder. The espresso machine pushes the water on to the coffee at nine bars or 130psi (pounds of force per square inch), and this is much more aggressively than a human can push down. The goal is simply to produce an even coffee bed, and do no more.
If they notice a little coffee stuck to the walls of the basket, some people will use the tamper to tap the handle to loosen them so they can be tamped down in to the coffee bed. Don’t tap. If you tap the handle, you may knock the puck of coffee loose from the walls of the basket, allowing the shot to channel. Secondly, you may damage your tamper and the nice ones are beautiful objects in their own right.
My final piece of advice is to hold the tamper properly. It should be held like a flashlight, with your thumb pointing straight down. When you apply pressure to the coffee, your elbow should be directly abo
ve it and your wrist should be straight. If you imagine a screwdriver in your hand, and a screw sticking directly up out of the work bench, you should put your arm in this same position as you push down in order to protect your wrists (see Espresso Method). Repeatedly performing this action incorrectly has given a huge number of professional baristas trouble with their wrists.
ESPRESSO METHOD
In this process we’re going to make two cups of espresso. These could go into two separate cups, or into one cup as a double espresso.
1 Fill the reservoir in the espresso machine with water with a low mineral content, suitable for brewing coffee, then switch on the machine to heat the water.
2 Grind the coffee just before you start brewing. Be sure to weigh the coffee first. A
3 Make sure the basket is clean. Wipe it with a small dry cloth to make sure it is dry and to remove any leftover grounds once you have tapped out the puck of coffee from the last brew. The cloth will help remove the oily residue from the last brew as well.
4 If you can, place the entire brew handle (also called the portafilter) on the scales to weigh out the coffee. If this is not possible, remove the basket from the handle and place it on the scales. B
5 If your scales are accurate enough, weigh the ground coffee to within 0.1g of your recipe, whether it is your own recipe carefully honed over time, or the recipe given to you by the roaster. This level of accuracy may seem like overkill, but digital scales are now relatively cheap and I promise that using a set of scales will help you make more delicious coffee more often.
The World Atlas of Coffee: From beans to brewing - coffees explored, explained and enjoyed Page 9
