What is espresso? Pressure, ratio and the grind it needs

How is espresso different from regular coffee?

The difference is pressure and concentration. Drip and pour-over use gravity and a coarser grind. Espresso forces water through a fine grind at about 9 bar, so it extracts quickly and ends up far stronger.

Coffee ad Astra gives the numbers. Espresso typically has 7% to 12% total dissolved solids, while filter coffee is around 1.3% to 1.45%. That is several times as concentrated.

A single shot is not more caffeinated than a mug of drip, though. Wikipedia puts a 30 ml shot at about 65 mg of caffeine, less per serving than drip coffee.

What is a standard espresso recipe?

There is a traditional Italian standard and a looser modern specialty approach. Wikipedia cites the Italian standard: about 7 g of coffee, water at 88°C, and a cup of about 25 ml.

Specialty cafes usually use more coffee and measure by weight. Perfect Daily Grind suggests 18 to 21 g of coffee and a 1:2 ratio, meaning twice the dose in liquid. Its typical shot time is 25 to 32 seconds, within a wider 22 to 40.

The ratios above follow Perfect Daily Grind's guide, which calls 1:1.5 a tighter, more concentrated shot; ristretto is the usual name for that style. The weight of liquid in the cup is called the yield.

Who invented espresso?

Several Italian inventors built it up over about 60 years. Wikipedia credits Angelo Moriondo with an 1884 patent for a steam-powered coffee machine. Luigi Bezzera filed a patent for a single-serving brewer in 1901, and Desiderio Pavoni began selling commercial machines in 1905.

The modern shot came later. Achille Gaggia's lever-piston machine reached much higher pressure and produced crema, and went on sale in 1948. The Faema E61 of 1961 introduced the electric pump.

How do you know if a shot is right?

Taste it. Perfect Daily Grind describes a good shot as having sweetness, pleasant acidity, cleanliness and a lasting finish.

Sour, salty and quick suggests under-extraction. Bitter, dry and hollow suggests over-extraction. Time and ratio are guides, but the cup decides.

What grind does espresso need?

A very fine grind, and a grinder that can adjust it in very small steps. Perfect Daily Grind's rule is simple: if the shot runs fast, grind finer; if it runs slow, grind coarser.

The hard part is how small those changes are. Baratza says a few dozen microns of burr movement can change a shot by several seconds. A grinder with large steps can leave the right setting between two clicks.

Baratza says this about its own Encore. It is "excellent for filter brewing or French Press" but the perfect shot "may lie in between two grind settings." Its Encore ESP fixes this with much smaller steps in its espresso range. Baratza also advises starting slightly coarser than you expect, then moving finer in small increments.

That is why espresso grinders are usually stepless or have very fine steps. See stepless grinders for the tradeoff. The grinder finder can filter to espresso-capable models.