Nitro cold brew

What the gas changes

CoffeeHQ explanation

Nitrogen dissolves very poorly in water, far less readily than the carbon dioxide used in fizzy drinks. It has to be forced in under pressure and comes straight back out when the pressure is released. Because so little is dissolved and it leaves so readily, it forms bubbles that are extremely small, and those bubbles rise slowly. That is the cascade in the glass and the dense, lasting foam on top.

Fine bubbles suspended in a liquid make it feel thicker and smoother in the mouth. Nitro cold brew is routinely described as creamy and as tasting sweeter than the same coffee served still, although nothing sweet has been added; the likeliest explanation is that texture and the absence of sharpness are read as sweetness. Unlike carbon dioxide, nitrogen does not form an acid in water, so it adds no bite or fizz.

What it does not change

Widely documented

Caffeine depends on how the cold brew was made and how much is in the glass, not on the gas. Nitro cold brew is often said to be stronger, and a serving can be, for a plain reason: it is normally served without ice, so a glass holds more coffee than the same glass of cold brew over ice. Some cafés also brew their nitro base more concentrated. Neither is an effect of nitrogen.

Nor does nitrogen improve a poor cold brew. A base that is flat, stale or over-steeped comes out of the tap flat, stale or over-steeped, with a pleasant texture.

From keg to glass

Widely documented

Making it at home

Widely documented

A countertop nitro dispenser

Small kegs that take single-use nitrogen cartridges and pour through a restrictor tap. They reproduce the café result closely. Use only the cartridges the maker specifies.

A cream whipper

Often suggested, with a caveat: the standard cartridges for cream whippers contain nitrous oxide, a different gas that dissolves more readily and gives a foamier, slightly sweet-tasting result. It is not the same drink, and the device should only be used as its maker directs.

No gas at all

Shaking cold brew hard in a sealed jar gives a brief froth and a softer texture. It fades in a minute, costs nothing, and shows whether the texture is what you were after.

When a glass falls flat

CoffeeHQ explanation

No cascade and a thin head

Usually because: Too little nitrogen dissolved: the keg was not cold enough, was not left long enough under pressure, or the cartridge was spent.

Change first: Chill the coffee thoroughly before charging, and give it time under pressure.

Good texture, dull flavour

Usually because: The cold brew underneath is stale or was steeped too long.

Change first: Fix the base batch; the gas cannot.

Cold brew strength

Too strong

Usually because: Served undiluted and without ice, from a base made as concentrate.

Change first: Dilute the cold brew to drinking strength before it goes into the keg.

Cold-brew batch and dilution calculator

Where it came from

Accounts differ

Nitro cold brew appeared in specialty coffee shops in the United States in the early 2010s, borrowing the kegs, gas and taps already used for draught stout, and spread to large chains and to cans within a few years. More than one roaster is credited with serving it first, and the accounts do not agree. CoffeeHQ does not adjudicate between them.

What to do next

• Cold brew — The base decides the flavour and the caffeine; this is how to make it well.
• Cold brew versus iced coffee — What steeping cold changes, before any gas is involved.
• Caffeine estimator — Estimates a serving from how the cold brew was made and how much is in the glass.
• Become a barista — A structured programme from dose and grind through milk, drinks and maintenance.