How to tamp for a perfect coffee

20 March 2013
How to tamp for a perfect coffee
I was recently thinking about correctly tamping becausea customer was interested in buying the La Marzocco Swift grinder, a high speed automatic tamping grinder with dual hopper. La Marzocco is one of the most prestigious brands of coffee equipment, and being our coffee roasted in Tuscany, the idea of a grinder designed and built in Florence had a certain appeal.

Nevertheless, my first reaction when I hear the word "automatic" related to the process of brewing a good cup of coffee was of dismay: I love tamping, it is one of the step of that ritual that produces a (hopefully) perfect espresso, one of the skills that any good barista should learn, but I'm the first to admit that using such a grinder not only give you a great consistency, it actually make a better coffee.

Let's go back to the basic of tamping, to understand how is this possible. First a little secret: tamping with a 15 kg of pressure - as usually reccommended in many braista courses - is not the best way to go. Here, I said it. Well, that partially not true: the problem is that when you manually tamp, the pressure applied compact only the top part of the bed, leaving the bottom quarter barely compacted at all, no matter how much pressure you can apply. The difference in the case of the La Marzocco Swift grinder is that the coffee is ground and tamped at the same time, starting from the bottom layer, and even if the pressure applied is probably just 5 kg, the result is a much more consistently compacted bed of coffee, every layer of it.

Ideally, with tamping you should create a bed of ground coffee even and level, so the hot water can be distributed evenly through it, extracting the maximum flavour. If the top layer is tamped very hard, and the barista knock the portafilter to be able to compact every bit of coffee, it is very likely that under pressure the hot water could partly find a way around the coffee and not through it.

Is therefore better not to knock the portafilter? Yes, at least after having settled out the coffee. To settle any loose ground coffee, it is much better to use a manual tamper a few millimeters smaller that the filter basket, even a couple of mm. This smaller tamper will allow you to compact all the coffee using a "cross" tamping, that is tamping at the four corners of an imaginary cross, trying to keep the bed as square as possible. You don't need to apply a great pressure, especially if you press the coffee after putting the first seven grams in the filter basket and you press it again after the second seven grams, but it is very important to apply an even pressure.

And what if, at the end, sometimes the quality of the coffee in a cup is not as expected? Throw it away: if the crema is weak or pale, better start again, making another coffee: you'll waste a few cents of coffee but you will have a much happier customer!

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