How to brew better coffee at home

Why weighing beats scoops

A scoop of coffee can weigh anything from 7 to 12 grams depending on the roast and the grind, so the same scoop gives a different cup every day. A cheap kitchen scale that reads to the gram fixes that, and it lets you measure the water too. Brewing by weight is the single biggest step up most people make.

1. The ratio

The ratio is how much water you use for each gram of coffee. It sets how strong the cup is. Most filter coffee tastes best somewhere between 1:15 (stronger) and 1:17 (lighter): 15 g of coffee to 250 g of water is about 1:16.7. The Specialty Coffee Association’s guideline for drip coffee works out at around 55 g of coffee a litre, close to 1:18, which suits large batch brewers. Immersion brews such as the French press often sit at the same ratios; espresso is about 1:2, and cold brew concentrate about 1:8 before it’s diluted.

• Stronger: 1:15
• Classic: 1:16 to 1:16.7
• Lighter: 1:17
• Espresso: 1:2 (grams of drink, not water)
• Cold brew concentrate: 1:8, then dilute about half and half

2. The grind

The grind decides how fast water can take flavour out of the coffee. Finer grounds have more surface, so they give up their flavour faster and also slow the water down. Coarser grounds do the opposite. That’s why each brewer has its own grind: a short espresso shot needs it fine, a four-minute French press needs it coarse.

Grind just before you brew. Ground coffee goes stale within minutes to hours, whole beans over weeks. A burr grinder gives even pieces; a blade grinder makes a mix of dust and chunks that brew unevenly.

3. The water

A cup of coffee is about 98 percent water, so it matters. Use clean, fresh water with no smell or taste of chlorine. Some minerals help: very soft or distilled water tastes flat and sour, very hard water tastes chalky and scales up your kettle. The Specialty Coffee Association publishes a water standard; in practice, filtered tap water or a gentle bottled water works well for most people.

4. The temperature

Hotter water extracts faster. For most brewing, aim for 90 to 96°C (195 to 205°F): that’s water just off the boil, after it has rested 20 to 30 seconds. Lighter roasts like the hotter end; dark roasts get bitter quickly and like it a little cooler. Cold brew uses cold water and makes up for it with many hours of time.

5. Fresh beans

Coffee is at its best a few days to a few weeks after roasting, so look for a roast date on the bag rather than a best-before. Very fresh beans are still giving off carbon dioxide, which can make a brew bubble and taste sharp: give filter coffee about 4 days and espresso about a week. After about a month the flavour fades. Keep beans in an airtight bag or tin, away from light and heat, and don’t keep them in the fridge, where they pick up moisture and smells.

Extraction: why coffee tastes sour or bitter

When water meets ground coffee, it dissolves the flavours in a rough order. Bright acids come out first, then sugars and sweetness, then the heavier bitter compounds. A brew that stops too early is under-extracted: sour, thin and short. One that goes too far is over-extracted: bitter, dry and hollow. The aim is to stop in the sweet middle.

Coffee people measure this with a refractometer: a well-extracted filter brew has taken about 18 to 22 percent of the coffee’s weight into the cup, at a strength of about 1.15 to 1.35 percent dissolved solids. You don’t need the gadget. Your tongue tells you which way to go.

Fixing a cup

Change one thing at a time, and change the grind first.

• Sour, sharp or thin: grind finer, or brew a little hotter or longer
• Bitter, harsh or dry: grind coarser, or brew a little cooler or shorter
• Weak or watery: use a little more coffee for the same water
• Too strong: use a little more water, or just top the cup up
• Flat or hollow: check the beans are fresh, and make sure every grain gets wet at the start

Sources

• Coffee standards (Specialty Coffee Association)
• Coffee preparation (Wikipedia)
• Coffee extraction and how to taste it (Barista Hustle)
• The most important thing about brewing coffee (Barista Hustle)
• The SCA Water Quality Handbook (Specialty Coffee Association)
• Coffee roasting (Wikipedia)