Cold brew, done properly

Cold brew is coffee steeped in cold or room-temperature water for many hours.

It is not iced coffee, which is hot-brewed coffee chilled. The two taste substantially different because the extraction chemistry differs.

Why it tastes the way it does

Temperature governs which compounds dissolve and how fast.

Many of the acidic compounds and some of the bitter ones extract poorly at low temperature. Sugars and some aromatics extract adequately given enough time.

The result is markedly lower perceived acidity, a smoother and sweeter profile, heavier body, and less brightness and aromatic complexity.

Whether that is an improvement depends on what you want. It is a genuine trade — you gain smoothness and lose articulation.

The immersion method

The straightforward approach.

Ratio. Around 1:8 for a concentrate to be diluted, or 1:15 for something ready to drink.

For a concentrate: one hundred grams of coffee to eight hundred grams of water.

Grind coarse. Coarser than French press. Fine grinds over twelve hours over-extract and produce muddiness, and they are nearly impossible to filter.

Combine and stir to ensure all grounds are wetted. Dry pockets extract nothing.

Steep twelve to eighteen hours, at room temperature or in the refrigerator.

Room temperature extracts faster, so twelve hours is adequate. Refrigerated needs longer, up to twenty-four.

Filter. Strain through a fine mesh first, then through paper or cloth for clarity.

Do not squeeze the grounds. Squeezing forces bitter compounds and fines through.

Store refrigerated and use within a week to ten days. Concentrate keeps longer than diluted.

The slow drip method

The other approach, using a tower that drips cold water through a bed of coffee over several hours.

Produces a cleaner, more delicate result than immersion — closer to a filter coffee in character while retaining the low acidity.

Requires equipment, patience and adjustment of the drip rate, typically aiming for one drop per second or so.

Visually impressive, genuinely different, and considerably more effort.

Dilution

Concentrate is diluted at serving, typically one part concentrate to two or three parts water or milk.

Adjust to taste. Concentrate strength varies with your ratio and steep time.

Diluting with milk produces a very different drink from diluting with water — richer, sweeter, and the standard form of the iced coffee sold commercially.

Choosing coffee for it

Medium to medium-dark roasts generally work best. The method already strips acidity, so a light roast can end up flat and hollow.

Chocolate, nut and caramel profiles suit it. Delicate florals largely disappear.

Natural processed coffees can be excellent, contributing fruit sweetness that survives the method.

It is also a reasonable use for slightly older coffee, since the method is forgiving. Not stale coffee, which will still taste stale, but a bag at week five rather than week two.

The caffeine question

Cold brew is frequently described as high in caffeine, and the answer depends on what you are comparing.

Per unit of concentrate, yes — it is brewed at a much tighter ratio.

Per finished drink after dilution, it is broadly comparable to other brewing methods.

Caffeine extracts reasonably well even at low temperature given twelve hours or more, so the long steep compensates for the low temperature.

The commercial cold brews with very high caffeine content are simply less diluted.

The acidity claim

Cold brew is often marketed as lower in acid and better for sensitive stomachs.

Measured pH differences between cold brew and hot brew are real and modest — cold brew is somewhat less acidic but not dramatically so.

Perceived acidity differs much more than measured acidity, because the compounds that taste bright are less extracted.

Whether this helps with digestive discomfort varies by individual, and the evidence is not strong enough to make a confident claim. Some people report it does. That is worth knowing and is not the same as established.

Nitro

Cold brew infused with nitrogen and dispensed under pressure.

Nitrogen produces very fine bubbles and a cascading effect, giving a creamy texture and a soft, sweet mouthfeel without any dairy.

It also slightly reduces perceived bitterness.

Home nitro systems exist using whipped cream chargers and are more equipment than most people want.

The practical routine

A jar of coffee and water on the counter before bed. Filtered in the morning. Enough concentrate for four or five days in the fridge.

It is the lowest-effort way to have good iced coffee available continuously, which is why it took over.