Is it a science, is it an art, do we worry too much about it?
Usually the main problems with tamping don’t come from technique, more usually it’s the grinder at fault (or sometimes the coffee if it’s stale). Many of the exotic techniques, which sometime even involve a “chant to the coffee gods whilst dancing in little circles”, are usually the result of poor and/or inconsistent grind. The more “exotic techniques” are simple methods that attempt (usually unsuccessfully) to overcome these deficiencies in grind.
Other things people try is exact dosing, weighing out the coffee to within 1 or 2 beans of a standard weight they want to use….all of this is a little obsessive to use in the every day scenario of just wanting a decent cup of coffee and certainly not possible in the busy “production” environment of a café.
I am definitely not going into advanced techniques. If you want the advanced stuff I think there have been books written on the subject…so let’s keep it very simple and basic:
You need a decent grinder (it’s going to cost some money and it’s probably fair to say that anything under £100 is not going to do the job…yeah sorry). Grinders in the OKish range are Iberital MC2 and similar, Good are the Eureka Mignon's, excellent are all of the Mazzers, Eureka Atom's, Zeniths and Olympus, ECM and Profitec. There are more exotic types and other types, but you need to be in the price brackets of the grinders mentioned).
You need a decent tamper, one that fits and not that crappy plastic thing they give away free. The biggest mistake most people make is to get a tamper that “fits” too closely. e.g for an Izzo Vivi basket, they are 58mm (but actually measure a bit larger than that, around 59mm once you are past the rim), people measure them and based on well meaning advice order a Reg Barber 58.5mm for that “extra snug fit”, this is bad news because the tamper ends up being problematic on the single basket, just about works on the double, but you get that “binding” up the sides with any coffee that gets there. I personally don’t like less than 0.5mm all round, this allows the tamper to work well in the single or the double.
Then curved or flat base…personally I prefer a flat base (but that’s up to you)
Weighing out the coffee is a bit obsessive, get to judging the whole thing by eye and you will soon become consistent. For a single, dose up to about 3-4mm from the top of the basket, for the double, level with the top works well. The main thing you have to avoid is the coffee “puck” touching the shower screen when you load the portafilter.
So to the “Tamp” itself
Fill the basket, tap the side with the flat of the hand to distribute the coffee as evenly as you can
Place on a stable surface…a tamping stand can help at this point (you don’t want it all wobbly)
Slowly apply pressure (between 20-30lbs, not as hard as you think!) with the tamper, whilst keeping it as upright as possible (you want the surface of the coffee “puck” to be level in the basket. Press too fast and you might get voids/loose areas.
As you release the pressure whilst still applying some light pressure (about 5lbs), twist the tamper (about 180 degrees) for that final polish.
Brush the flat of your hand across the rim if the portafilter to remove any stray to remove stray grounds
That’s it you have that nice coffee “puck” we have been talking about.
I never tap or do anything to disturb the puck after tamping:
Main success criteria:
I used to muck about a lot a long time ago….don't bother now….a sort of less is more philosophy….works for me.
Whole tamp process takes a few seconds
P.S. If you find that tamping pressure has a very big effect on extraction times….possibly your grinder has a problem or is producing an inconsistent grind.