If you use a lever machine & are moving to real fresh roasted coffee, and assuming you have a decent grinder, it is very easy to over-extract the coffee as the moisture content in genuinely fresh roasted coffee is much higher than in beans that are just claimed to be ‘fresh roasted’. In fact it is so noticeable that if you rub a few freshly roasted grinds between your forefinger & thumb you will feel the dampness. This is a key indicator of a fresh roast. As is a dense, generous crema flowing from the portafilter.

Arabica beans produce less crema than robusta, and the crema from arabica beans drops off quickly as the beans stale. To combat this many roasters add robusta to aid in the production of crema but you will never see a bean of robusta in a Londinium roast unless you ask for it in your bespoke roast. We don’t have a downer on robusta, but just bear in mind that a 100% arabica roast has to be extremely fresh to give you a dense, generous crema. Commit this to memory as it is a rare fact in a coffee world congested with opinion, misinformation & grandstanding.

How is the risk of over-extraction greater for a lever machine than an electric pump machine?

Well domestic electric pump machines choke very easily, which alerts you to the problem in a fairly obvious manner (no coffee runs from the machine)

With a lever machine machine, especially those of us with a macho streak, it is very easy to just swing on the lever harder & harder & and a brown liquid, however unpalatable will eventually flow from the machine

If you are using your lever machine as a home gym you’re probably over-extracting the coffee

Simply set your grinder a mark or two coarser. You’ll will notice the drop in resistance on the lever immediately.

The ‘correct’ amount of resistance can only be learnt with experience, but suffice to say it should only be moderate. If your lever machine is like the tight lid of a jam jar & your partner is always asking you to make the coffee because they find the lever too hard to pull down, then that is definitely too much pressure. In short, if the pressure is right your grandmother should be able to pull a shot on your lever machine

Obviously the pressure needs to be more than just ‘nominal’, but if the pressure on the lever is too low it will be evident with thin coffee that is more like filter coffee than the thick, dense composition and accompanying crema that are the hallmark of espresso

If you take a while to work your way through a 250g bag of coffee you will find that you need to notch the grinder to a slightly finer setting as the coffee ages and the moisture content in the coffee drops, meaning the grounds bind together less easily, therefore demanding a finer grind