GRINDING AND PREPARATION @museum.de

Once you’ve selected the right kind of coffee, it’s all about the grind. Whether you grind the beans by hand or with an electric grinder is less important. What matters is the grinding mechanism and how fine the grind is. A cone grinder works best. Blades that chop the coffee seeds are less advisable, because the ground coffee may overheat and the essential oils become scorched.

The following rule of thumb applies to the grind: the longer the water is in contact with the coffee, the coarser should be the grind. You need a fairly coarse grind for a coffee pot with a plunger, where the coffee is compressed with a sieve or poured through a strainer after 2 or 3 minutes of brewing time. For a long time, that was the traditional method of making coffee – until the development of the coffee filter.

There were many attempts to stop coffee grounds getting into the cup – and then the German housewife Melitta Bentz from Dresden came up with the idea of trying a strainer combined with a paper filter. She used a brass flower pot, drilled holes in the bottom and placed a paper filter inside – one she’d made out of blotting paper from her son's exercise book. In 1908, this inventive lady applied for a patent on her idea – the coffee strainer with filter paper. And although there are now other filter systems, in Germany, the brand name Melitta is still synonymous with “coffee filter”.

Preparing filter coffee is quite unlike making an espresso. In that process, water is forced through finely ground and compacted coffee powder at high pressure to produce an extract. Espresso coffees are roasted for longer than filter coffees, so they generally tend be Robusta blends.

A lot of people believe that an espresso must contain a lot of caffeine. And indeed, caffeine levels in the Robusta plant are twice as high as in the Arabica plant. But the amount of caffeine in your cup of coffee depends on how much time the coffee powder was exposed to the water. If the water percolates through the coffee for about 20 to 25 seconds, not much caffeine is extracted. So coffee from an espresso machine contains less caffeine than filter coffee.

Arabica beans are not really suitable for making espresso, because when compacted, they lose their subtle flavour, may develop extreme acidity, and fail to develop a perfect crema – that’s the thin layer of brown foam on top of a freshly made espresso.

In the display area that deals with coffee-making methods, we also have a sample case once carried by a coffee rep in the 1950s. The case contains everything cafés or restaurants would have needed to serve coffee at the time.