The Sour Formula: One Ratio, Twenty Drinks

Two parts spirit, one part citrus, one part sweet. Shake with ice, strain. That is the sour, and it is the most productive thing you can memorise about cocktails, because a dozen famous drinks are the same formula with the base swapped.

• 60 ml spirit
• 30 ml citrus
• 30 ml sweetener
• Shake hard with ice, 10 to 15 seconds, and strain

The same drink, four names

• Rum and lime is a Daiquiri.
• Gin and lime is a Gimlet.
• Whiskey and lemon is a Whiskey Sour.
• Brandy and lemon, with orange liqueur as the sweetener, is a Sidecar.
• Tequila and lime, again with orange liqueur, is a Margarita.

Once you see it, most cocktail menus become legible. A drink you have never heard of with a spirit, a citrus and a liqueur in it is a sour, and you already know roughly how it will taste and exactly how to make it.

The three levers

The ratio

2:1:1 is the starting point, not the answer. It suits a 40% spirit and a 1:1 syrup. Move it as follows:

• Too sharp? More sweetener, 5 ml at a time. Not less citrus, which flattens the drink instead of balancing it.
• Too sweet or too soft? More spirit, or a drier sweetener. A 2.5:1:0.75 ratio is where a lot of modern bars sit.
• Using a liqueur as the sweetener? It is weaker than the spirit and sweeter than syrup, so the drink gets both softer and sweeter. This is why a Margarita is often built 2:1:1 and still reads sweet with a cheap triple sec.

The citrus

Lime is sharper and more aromatic, lemon is rounder and less floral. They are broadly interchangeable in the formula and not interchangeable in a drink with a name: a Margarita made with lemon is a good drink that is not a Margarita. There is more on that in what to use when you are out of limes.

Fresh, always. Bottled juice is pasteurised, so the aromatic oils are gone and you are left with acidity and no smell. A sour is a drink where the citrus is a quarter of the volume, and it cannot afford that.

The sweetener

Simple syrup is the neutral option and the one the ratio assumes. Swapping it changes the drink's character more than its balance:

• Honey syrup and gin makes a Bee's Knees.
• Demerara syrup suits aged spirits.
• Orange liqueur gives you the Margarita and Sidecar family.
• Amaretto is sweet enough to be the entire sweetener, which is what an Amaretto Sour is.

Ratios and shelf life for the syrup itself are in the simple syrup guide.

The additions

Three things get added to the base formula often enough to be worth knowing.

Egg white, about 15 ml, gives the drink a dense white head and a rounder texture. It adds almost no flavour. Dry shake first, without ice, then shake again with ice.

Bitters, two dashes, on top of the foam or in the shake. They do for a sour what salt does for food.

Soda, to lengthen. A sour topped with soda is a Collins, so a Tom Collins is a gin sour in a tall glass with soda, and it is the same drink you already know at half the strength.

Why it works

Sweet and sour suppress each other on the palate. Sugar alone is cloying, citrus alone is harsh, and in roughly equal measure each one hides the other's excess and what comes through instead is the spirit. That is the whole trick, and it is why the ratio has survived essentially unchanged since the 1860s.

Every drink in the sour category is a variation on it, and most of the three-ingredient classics are too.