Before you beginBefore you start this is what you need:
- The coffee with which you're calibrating the espresso grinder
- Assuming it is a doserless grinder with a timer, then an understanding of the grinder, viz. how to adjust its grind size from coarse to fine, and how to adjust the timer setting (get the manual from the internet if required).
- A scale that can fit the filter basket that is being used in the espresso machine. Ideally one that can fit the portafilter as well.
- Ideally a second scale to measure the dose of the brewed cup. You can use one scale but this takes longer.
- A timer (a phone is fine usually).
- You also need to understand the capacity of your filter basket. If it is a calibrated basket it will have a grammage written on the side of the basket (or a code you can look up). If not then you need to assume that it is an uncalibrated basket. A double basket takes 14g and a single takes 7g. A double is about a thumb knuckle's depth from top to bottom. A single is either shallower, or has two parts in the basket -- one for the grinds, and one for stopping the tamper. This is a generalization, however. It is best to use a calibrated or precision basket like a Strada, VST or IMS for accuracy of extraction.
- Preferably standard items like cups and tamper, a mat if possible etc.
Portafilter with an 18g IMS calibrated basket and a 7g or single uncalibrated basket
Setup of grind sizeOnce you have all your goodies, set up your grind for fineness or coarseness.
- Using your grinder, grind a portion of coffee at least at the dose size your basket recommends. You can do this into the basket in the portafilter (if your scale can take both), or you can do this into the basket or a separate container.
- After taring your scale, adjust the grammage (with a spoon) within an accuracy of about .1g or 100mg.
- Tamp the coffee. Get ready to pull a shot.
- Place the scale on the espresso machine, tare it with the cup (or as the scale recommends) and then insert the portafilter and pull an espresso. You are aiming to pull between 1.5 times the dose and 2 times the dose, in 25 seconds ideally, not shorter than 15 seconds,and not longer than 45 seconds. Anything over 60 seconds adds no value to the brew.
- You want to see slow infusion. Within 4 seconds the coffee should start running out of the portafilter into the cup.
- If nothing comes out after 10 seconds, your grind is too fine.
- If it runs too quickly, your grind is too coarse.
- If it begins slowly, accelerating a little as it extracts, creating almost a gentle "S", what some call mouse tails, you have hit the spot.
- If you nailed it, feel free to try it again. Otherwise continue to Setup of timer on grinder. If not, adjust the grinder (grind out remainders from the previous grind so as to avoid mixing) and repeat the above steps until you are happy. This requires patience and concentration.
Example of mouse tails in espresso