Espresso and Milk

Coffee Fundamentals

Course 1 · Chapter 8 · Espresso and Milk: The Machine and the Menu

What Espresso Is

Wikipedia's Espresso article defines it as a concentrated coffee made by forcing hot water under high pressure through finely ground coffee, served in about 25 to 30 ml portions. It has a dark body topped with a lighter foam called crema, a dense foam of emulsified oils that the article says forms when high-pressure water dissolves more carbon dioxide left from roasting. Chapter 6 gave the family (pressure), the temperature and the pressure range; this chapter fills in the details.

A Reference Shot

The article quotes a standard from the Italian Espresso National Institute (INEI). Here it is beside what the article calls typical.

Quantity	INEI standard	Typical (article)
Dose	7 ± 0.5 g of ground coffee	Single, double and triple baskets use roughly 7, 14 and 21 g
Water pressure	9 ± 1 bar at entry	Pump machines about 9 bar since the Faema E61
Water temperature	88 ± 2 °C leaving the unit; 67 ± 3 °C in the cup	Chapter 6: 91 to 95 °C
Time	25 ± 5 seconds	Usually 25 to 30 seconds
Volume in cup	25 ± 2.5 ml including crema	25 to 30 ml

Temperatures from different places

The INEI figure of 88 ± 2 °C is for water leaving the unit; chapter 6 quoted 91 to 95 °C from the Coffee preparation article. I did not find a source that reconciles them (check). The espresso machine article gives no brew temperature at all. Also, chapter 6 gave espresso pressure as 8 to 18 bar; the espresso article's own standard is 9 ± 1 bar, and the machine article gives 8 to 10 bar for spring piston machines. These describe different machines and standards, not an error, but the ranges differ.

Shot variants

Name	Volume	Note
Ristretto	About 20 ml	Shorter than a standard shot
Espresso	25 to 30 ml	The standard
Lungo	About 60 ml	Pulled with twice the water

The Machine

The espresso machine article describes a portafilter (group handle) that holds a tamped puck of grounds in a basket and attaches to the grouphead, sealing against a gasket. It is usually brass for heat retention. A bottomless portafilter lets a barista check for "channeling", water carving a path through the puck. It also describes boiler layouts:

Type	How it works (from the article)
Single boiler (SB)	Brews only, no steam
Single boiler, dual use	One chamber for brewing and steaming, one operation at a time, with a warm-up period
Heat exchanger (HX)	One boiler at steaming temperature; brew water cooled by a flush of 4 to 6 seconds before the first pull
Dual boiler (DB)	Separate brew and steam heating

Auxiliary steam wands heat and froth milk, and can make microfoam for latte art. Operation is manual, semi-automatic or fully automatic (superautomatic). The article marks several of its machine sections as needing more citations (check).

How it developed

Year	Event (from the articles)
1884	Angelo Moriondo of Turin patents a steam-driven machine that brews in bulk (the machine article gives 16 May)
1901-1902	Luigi Bezzera of Milan applies for (Dec 1901) and is granted (Jun 1902) patents for individual servings
1903-1905	Desiderio Pavoni buys the patents and begins selling machines, generally considered the first commercial espresso machines
1935	Francesco Illy patents the compressed-air Illetta
1938-1948	Achille Gaggia patents a hand-pulled piston design (1938); the piston machine goes on sale in 1947 to 1948 and is marketed as "crema caffe"
1961	Ernesto Valente invents the Faema E61 with an electric pump to 9 bar
1970	The La Marzocco GS is the first dual boiler (machine article)

The machine article dates Gaggia's piston machine to 1945, while the espresso article has the patent in 1938 and sales in 1947 to 1948; these may be different milestones, but I did not resolve which is which (check).

Milk Drinks

The Espresso article lists drink volumes; the Cappuccino article adds composition.

Drink	Volume (Espresso article)	What it is
Macchiato	30 to 40 ml	Espresso with milk foam
Americano	150 to 180 ml	Espresso topped with hot water, a 1:5 ratio
Long black	150 to 180 ml	Espresso poured over hot water
Cappuccino	150 to 180 ml	A large amount of milk and foam
Caffè latte	250 to 280 ml	At least 210 g of milk at 58 to 70 °C
Latte macchiato	250 ml	Milk and foam first, then espresso

The Cappuccino article gives the traditional ratio as equal thirds of espresso, steamed milk and milk foam, with the Italian standard being 25 ml of espresso and the rest of the cup split evenly between milk and foam. Milk is steamed to about 55 to 65 °C, and World Barista Championship rules want foam at least 1 cm deep. The traditional cup is small with a handle, 180 ml at most; chains in the US often serve 360 ml or more. The same article says a latte has the same espresso with more milk and microfoam (200 to 300 ml), a flat white is a cappuccino with textured milk and little or no foam on top in a small cup, and a macchiato is a much shorter drink with only a little milk.

The name

Cappuccino refers to the colour of Capuchin friars' robes. The popular story that it was named after Marco d'Aviano is called "popular but unverified" in the article, and the Italian word is first documented in the 19th century.

Code: Shot Arithmetic

The script below works with the INEI numbers: the ratio of drink volume to dose, basket scaling, and a 150 ml cappuccino split. I ran it to get the output shown.

BASKET_DOSE_G = {"single": 7, "double": 14, "triple": 21}

def shot_ratio(dose_g, yield_ml):
    return yield_ml / dose_g

print("Standard shot (7 g -> 25 ml):", f"1:{shot_ratio(7, 25):.1f}")
for name, dose in BASKET_DOSE_G.items():
    print(f"{name} basket: {dose} g -> about {dose * 25 / 7:.0f} ml at the same ratio")

for name, ml in [("ristretto", 20), ("espresso", 25), ("lungo", 60)]:
    print(f"{name}: {ml} ml from 7 g = 1:{shot_ratio(7, ml):.1f}")

total = 150
espresso = 25
rest = total - espresso
print(f"Cappuccino {total} ml: {espresso} ml espresso + {rest/2:.1f} ml milk + {rest/2:.1f} ml foam")
print(f"Americano at 1:5 from a 25 ml shot: {25 * 5} ml of drink total")

def c_to_f(c):
    return c * 9 / 5 + 32
print(f"Milk 55-65 C = {c_to_f(55):.0f}-{c_to_f(65):.0f} F")

# Output
Standard shot (7 g -> 25 ml): 1:3.6
single basket: 7 g -> about 25 ml at the same ratio
double basket: 14 g -> about 50 ml at the same ratio
triple basket: 21 g -> about 75 ml at the same ratio
ristretto: 20 ml from 7 g = 1:2.9
espresso: 25 ml from 7 g = 1:3.6
lungo: 60 ml from 7 g = 1:8.6
Cappuccino 150 ml: 25 ml espresso + 62.5 ml milk + 62.5 ml foam
Americano at 1:5 from a 25 ml shot: 125 ml of drink total
Milk 55-65 C = 131-149 F

Reading the output

By volume a standard shot is about 1:3.6, not the 1:2 of chapter 6. That figure was by weight, and a shot with crema takes up more volume than it weighs, so the two are not directly comparable (my explanation, not the article's; check). The Americano line gives 125 ml, below the article's 150 to 180 ml, so the article's drink size and its 1:5 ratio do not obviously fit a single 25 ml shot; perhaps a double shot is meant, which I could not confirm (check).

Not Yet Verified, and Sources

Sources. Wikipedia articles Espresso, Espresso machine and Cappuccino. The Espresso article is about 126,000 characters and I read the first 100,000; the unread tail looked like navigation and templates. The Cappuccino article was read to about 100,000 of 106,000 characters. I saw them through a summarising tool.
Conflicts. Espresso temperature (88 versus 91 to 95 °C), pressure ranges, Gaggia's dates, latte volume (250 to 280 ml versus 200 to 300 ml across articles), the "caffè crema" volume inside the Espresso article, and the Americano ratio. Not resolved.
Weak support. Several machine-article sections are marked as needing more citations.
Not in the pages read. A numeric brew temperature in the machine article, tamping pressure, and the flat white's exact size (all marked check).
Not tested. I made no drinks; the script is arithmetic only.

Exercises

Exercise 1

Describe the INEI reference shot in one sentence (dose, pressure, time, volume). Then name two reasons the chapter gives for treating its numbers cautiously.

→ Solution

Exercise 2

Use the script to work out the volume and dose ratio for a ristretto from a double basket (14 g) giving 40 ml, and the milk and foam amounts for a 180 ml cappuccino with a 25 ml shot. Run it and compare with the traditional equal-thirds rule.

→ Solution

Exercise 3

Make a table of the drinks in the chapter ordered by size, with one distinguishing feature each. Then pick one pair that the articles describe differently (for example latte and cappuccino) and explain the difference.

→ Solution

Quick Reference

INEI shot: 7 g, 9 bar, 25 seconds, 25 ml, 88 °C at the unit
Variants: ristretto about 20 ml, lungo about 60 ml
Machine milestones: 1884 Moriondo, 1901 Bezzera, 1903 Pavoni, 1961 Faema E61
Cappuccino: thirds of espresso, milk and foam; milk 55 to 65 °C
Latte: more milk and microfoam; 200 to 300 ml

Coming next

Coffee Fundamentals 9 moves from making coffee to tasting it.