The Sour
Spirit, citrus and sugar in a fixed proportion, shaken. The largest family in the book, and the one whose ratio does the most work.
The formula
60 ml : 23 ml : 23 ml
- Spirit
- Two parts, and the only slot with enough volume to be tasted as itself. Everything else in the drink is measured against it, so lowering it does not make a lighter sour — it makes a drink of citrus and sugar with a spirit in it.
- Citrus
- Three quarters of a part of fresh juice, near six per cent acid. It is what stops the sugar reading as sweetness, and it is the slot that goes off: bottled juice has lost most of its aromatics and some of its acid, which is why a sour made with it tastes flat rather than sour.
- Sweetener
- Matched to the citrus, which is the whole trick. The pair cancel each other and what is left is body, so moving one without the other changes the drink twice — once in taste and once in texture.
Stated as the volumes a bartender pours rather than as bare ratio numbers, because a ratio has to be a ratio of something. Members depart from it, and where they do, their own page shows by how much.
Two parts spirit, three quarters of a part citrus, three quarters of a part sugar. Almost every shaken drink is this shape with one slot changed, and the proportion is close enough to universal that a bartender given an unfamiliar spirit will reach for it before anything else.
The ratio exists because sugar and acid cancel each other in a specific way. A sour is not sweet and it is not sour; it is both at once, and the sensation of balance comes from the two being present in roughly matching quantities rather than from either being restrained. Take the sugar out and the acid is unbearable. Take the acid out and the sugar is cloying. This is why the family resists the instruction to adjust to taste more than any other: moving one slot without the other does not make the drink sweeter or sharper, it makes it unbalanced.
The **spirit** slot is the most open in the book. Whisky, rum, gin, brandy, pisco, agave and tequila all work, and each named result is its own drink rather than a variant.
The **citrus** slot is lemon or lime, and the choice is not interchangeable. Both juices measure near six per cent acid, so the drink's sourness barely moves; what moves is the aromatic. Lemon reads clean and slightly floral against brown spirits, lime reads greener and sharper against white ones, and swapping them is a flavour decision that the arithmetic will not show.
The **sugar** slot is where the family branches. Plain syrup keeps the spirit in front. A richer syrup delivers the same sweetness in less liquid and leaves the drink heavier. Honey, orgeat, demerara and maple each bring a flavour of their own, and several of the drinks with their own names are a sour with nothing changed but this.
A **fourth slot is optional and defines a sub-branch**: egg white. It adds no flavour worth mentioning and changes everything about how the drink reads, turning acid that had been sharp into something rounded, and adding a head that holds the aromatics over the glass. It also lengthens the shake, which is why this branch takes on more water than a plain sour and finishes a little weaker.