Graduated shot glasses

Catches an espresso where the barista can watch it, and gives a rough volume reference for splitting or judging a shot away from the scale.

A small heavy-based glass, usually with graduations moulded or etched into the wall. The mechanism is trivial; the honest part is what it actually measures, which is VOLUME — and espresso volume includes crema, which is foam. Foam volume moves with the freshness of the coffee, the grind and the temperature, so two shots of identical mass can stand at visibly different heights in the same glass, and one shot read a minute after it was pulled stands lower than it did when it stopped. That is the whole reason a graduated glass is an indicator and a scale is a measurement: they answer different questions and neither replaces the other. What a glass is genuinely good at is everything the scale cannot show — the colour and continuity of the stream, the exact moment flow goes pale, whether two spouts are running at the same rate, and giving the barista somewhere to taste from that is not a guest's cup. Its other real property is thermal. A small glass has little mass, but so does a small drink, and a glass straight out of a cold cupboard takes a meaningful share of the heat out of an espresso before anyone drinks it.

• Decide first that this is not your yield instrument, and make sure the team knows it. Yield is mass and only a scale reads mass; a graduated glass reads volume including crema, which varies with the coffee's age. A bar that calibrates from the line on a glass is calibrating against how much foam today's beans produce, and it will chase the grind every time a fresh bag is opened.
• Buy it for what it is genuinely best at: watching. The stream's colour, the point it goes pale, and whether both spouts run evenly are all invisible in a ceramic cup and all diagnostic. On a bar with no bottomless portafilter, this glass is the cheapest window into the shot that exists.
• Insist on etched or moulded graduations, never printed. Printed lines fade in a commercial dishwasher within months, and a faded measuring tool is more dangerous than no measuring tool because the team keeps reading it.
• Weight the base and check the rim thickness in the hand. These get knocked, stacked and dropped into a sink of cutlery all day, and a chipped rim on a food-contact vessel is a discard, not a repair. Base mass buys survival; a thin rim buys breakage.
• Decide where they are stored, because that decides their temperature. A small glass out of a cold cupboard measurably cools a small drink, and glasses kept on the machine's warming surface behave differently from glasses kept below the counter — pick one and be consistent, because an inconsistent glass temperature is an inconsistent drink.
• Count for the peak and for the wash cycle together, not for the number of drinks. A tasting or split-shot glass used once and sent to the wash is out of service for the whole cycle, so the working count is however many are needed between washes.
• Keep the tasting glass out of service rotation entirely. A dedicated calibration glass that is never handed to a guest can be filled, tasted, rinsed and refilled all morning, and it stops calibration competing with service for clean glassware.