Why cold brew earns its place in your kitchen

Cold brew is not simply iced coffee. It is a different drink altogether, made by steeping ground coffee in cold water for half a day rather than forcing hot water through it in seconds. Because no heat is involved, you extract fewer of the bitter, acidic compounds and more of the smooth, chocolatey, caramel sweetness that sits in the bean. The result is mellow, almost syrupy, and it stays fresh in the fridge for a fortnight or so.

The real charm for a home brewer is the concentrate. Instead of faffing about every morning, you make one batch, keep it in a bottle, and dilute a glass whenever you fancy it. It also opens the door to iced lattes, coffee tonic, and a decent homemade espresso martini without ever switching the kettle on.

What you need, and the all-important ratio

You do not need expensive kit. A large jar, a cafetière, or a purpose-made cold brew filter all work. Beyond that, a fine sieve, some muslin or a clean tea towel, a funnel, and a glass bottle with a lid will see you right.

• 100 g coffee to 500 ml water gives a strong concentrate, roughly a 1:5 ratio. This is the one to start with.
• For a lighter brew ready to drink straight, loosen it to 1:8 — about 60 g per 500 ml.
• Use coarse ground coffee, the texture of sea salt or rough sand. Too fine and you will end up with mud and bitterness.
• A medium or medium-dark roast suits cold brew beautifully. Very light roasts can taste thin and grassy without heat to open them up.
• Filtered or bottled water makes a genuine difference. If your tap water tastes strongly of chlorine, so will your coffee.

Grind fresh if you can, and grind coarse — most supermarkets and roasters will do it for you if you ask for a cafetière grind.

The steep: twelve to eighteen hours

Tip the coffee into your jar, add the water, and give it a good stir to make sure every ground is wet. Cover it — a lid, a plate, or cling film is fine — and leave it on the worktop for 12 to 18 hours. Stir once more after a couple of hours if you remember; it helps the extraction along evenly.

If you prefer a cleaner, softer brew, put the jar in the fridge instead and leave it for 18 to 24 hours. The cold slows everything down, so you get less bite and a rounder flavour. Room temperature is faster and punchier; the fridge is gentler. Both work.

Do not leave it much beyond 24 hours. The grounds will start giving up harsh, woody notes and your lovely concentrate will turn muddy and dull.

Straining, bottling and storing

Strain in two stages for the clearest result. First tip the slurry through a sieve lined with muslin, or plunge a cafetière slowly. Then pass the liquid through a paper coffee filter set in a funnel. It is slow — sometimes half an hour — but worth the patience.

• Do not wring the grounds out hard. A gentle press is fine; squeezing aggressively releases fine grit and bitterness.
• Decant into a clean glass bottle, seal it, and label it with the date.
• Keep it in the fridge and drink within two weeks. Discard it if it smells sour or turns slimy.
• Freeze leftovers in an ice cube tray. Drop those cubes into your next glass instead of watery ice.

Diluting and serving

Your concentrate is roughly four times stronger than drinking strength, so dilute to taste. Start with one part concentrate to one part water for a black iced coffee, or one to two if you like it gentler. For an iced latte, swap the water for cold milk — oat and whole milk both work a treat.

Pour it over plenty of ice, ideally cubes made from coffee so the drink does not dilute as they melt. A few ideas worth trying:

• Top with tonic water and a strip of orange peel for a bracing summer cooler.
• Sweeten with a syrup rather than sugar granules, which will not dissolve in cold liquid.
• Add a tiny pinch of salt to a glass to soften any lingering bitterness.
• Warm a diluted measure gently on the hob if you fancy it hot — just do not boil it.

When it goes wrong

Too bitter? Your grind was too fine or you steeped too long. Go coarser and pull it back to twelve hours. Too weak? Use more coffee, not more time. Gritty or cloudy? Filter it a second time through paper. And never be tempted to speed things up with warm water — that is just hot brewing with extra steps, and you will lose everything that makes cold brew special.

Once you have your ratio dialled in, you can nudge it batch by batch: a touch sweeter, a touch stronger, a different roast. That quiet tinkering is half the pleasure.