Dialling in filter coffee

The order to work in

CoffeeHQ explanation

Common practice, arranged so that each brew answers one question.

1. 1. Fix the recipe by weight. Weigh the coffee and the water. Around 60 grams of coffee per litre of water is a common place to start; it is a starting point, and many people settle a little either side of it. Keep it fixed while you sort out the balance.
2. 2. Brew, and watch the bed. Note how long the brew took from first pour to last drip, and look at the bed afterwards. Flat and even, with fine grounds a little way up the paper, means the water passed through evenly. A crater, a hole or grounds stranded high and dry means it did not.
3. 3. Taste, then test strength. If the cup is unpleasant and also intense, add a little hot water, a teaspoon at a time, and taste again. A fault that fades was at least partly strength. A fault that stays is about balance.
4. 4. For balance, change the grind. Sharp and thin: grind finer. Bitter or drying and slow: grind coarser. Move a clear step, enough that the drawdown visibly changes, and keep the recipe, the water temperature and your pouring as they were.
5. 5. For strength, change the ratio. Balanced and thin: use about a tenth more coffee for the same water. Balanced and too intense: about a tenth less, or simply add water to the cup. A different dose makes a deeper or shallower bed, so expect the drawdown to shift a little.
6. 6. Then the smaller levers. Water temperature and pouring come after grind and ratio, because their effects are smaller and harder to repeat. Use hotter water for a light roast that stays sharp; pour more gently for a cup that stays drying.
7. 7. Write it down. Coffee, roast date, dose, water, grinder setting, brew time, and three words about the taste. Next week's bag starts from there.

One change per brew. If two things change and the cup improves, you will not know which did it.

What each control changes

CoffeeHQ explanation

Directions, not amounts. How far each moves a cup depends on the brewer, the grinder and the coffee.

Dose and water

The ratio sets strength: how much dissolved coffee is in the cup. It is the firm control and the one to settle by arithmetic. Taking more from the same coffee does make a cup a little stronger, but it changes the balance with it, so it is not the way to fix a cup that is balanced and thin.

Grind

A finer grind exposes more surface and slows the water, and both usually take more from the coffee. It is the main control over balance. A grinder makes a spread of sizes, not one size, and the finest share grows as the setting goes finer.

Water temperature

A smaller lever than its reputation. A trained panel found little difference between drip brews made at 87, 90 and 93 degrees Celsius once strength and extraction were matched. Hotter water does extract more readily, so in practice it is used for light roasts that stay sharp, and slightly cooler water for dark roasts that stay bitter.

Pouring and agitation

Pouring stirs the bed. A fast or high pour, a swirl or a stir moves the grounds and extracts more; a slow, low pour disturbs them less. More agitation is also more chance of an uneven bed. Whatever you do, do it the same way each time, or the pour becomes the thing that changed.

Drawdown

How long the water takes to drain is a reading, not a control. It reports the grind, the depth of the bed, the paper and how much you stirred. Compare it only with your own last brew of the same recipe in the same brewer.

Bypass

Water that reaches the cup without passing through the coffee: poured onto bare paper, run down the filter wall, or added afterwards on purpose. Unintended, it thins the brew. Intended, it is the cleanest way to lower strength, because it changes nothing about what was extracted.

Fines

The very finest particles fit into the gaps between larger ones and make a bed less permeable. That they travel with the water and block the paper is long proposed and little tested. In practice, a slick of fine mud on the paper after a slow brew is the sign to grind coarser or stir less.

Cone, flat bed and Chemex

CoffeeHQ explanation

The same recipe behaves differently in different brewers. A modelling study of packed coffee beds found flow through a cylindrical bed close to even from top to bottom, and markedly uneven flow in a bed shaped like a truncated cone. That was a model of beds in general, not a test of any brewer here, and what follows is how brewers describe each shape.

Conical brewers (V60 and similar)

One large opening and little to hold the water back besides the coffee and the paper. Drawdown answers strongly to grind and to pouring, which makes a cone responsive and easy to get uneven. A deep bed concentrates the flow towards its tip.

Flat-bottomed brewers (Kalita Wave and similar)

A shallow, level bed draining through a few small holes. It is usually described as more forgiving of pouring. It can slow if fine particles settle over the holes, and water poured onto the fluted paper wall runs past the coffee.

Chemex

The paper is thick and drains slowly by design, so a Chemex runs slower than other pour-overs at the same grind and is usually ground a little coarser. The wet filter can seal against the pouring channel and stall the brew; the three-layer side goes against the channel so air can escape.

Automatic filter machines

The machine sets the water's temperature and timing. Grind, ratio and batch size are what is left, and a small batch in a large machine makes a shallow bed that water passes quickly.

The same symptom, different causes

CoffeeHQ explanation

Six cups. In each pair the first word is the same and the first change is not, because the second observation changes what the first one means.

Sour and weak

Usually because: Too little was taken from the coffee, and with the recipe fixed that lowers strength as well. Adding coffee first would make a stronger sour cup.

Change first: Grind finer by a clear step.

Coffee too sour

Sour and strong

Usually because: In the one trained-panel study read, sourness rose with strength as well as falling with extraction. A heavy, sharp cup is asking for a weaker recipe first; grinding coarser to lighten it would make the sharpness worse.

Change first: Use about a tenth less coffee for the same water.

Work out the new recipe

Bitter and slow

Usually because: Flow and taste agree: the grind is fine for this coffee, the water stayed long and took a great deal. The paper will usually show a coat of fine mud.

Change first: Grind coarser by a clear step.

Coffee too bitter

Bitter and fast

Usually because: A quick brew that is still bitter is unlikely to have had too much taken from all of it. It may be strong, a dark roast, or a channel that over-worked part of the bed. Grinding coarser would only make it quicker.

Change first: Keep the grind and use about a tenth less coffee.

Make my coffee better

The drawdown stalls

Usually because: Either the bed has clogged (a fine grind, a lot of fine particles, heavy stirring) or the filter has sealed against the brewer so that air cannot escape. Lifting the edge of the filter tells you which: if the flow restarts, it was an air lock and the coffee is not at fault.

Change first: If lifting the filter does nothing, grind coarser by a clear step.

Pour-over stalling

Sour and bitter at once

Usually because: Part of the bed gave up a lot and the rest very little, and the cup is an average of the two. A grind change will swing it from one fault to the other without settling.

Change first: Leave the grind, wet all of the coffee in the bloom, and pour to finish with a flat bed.

Uneven pour-over bed

Why no brew time is given

CoffeeHQ explanation

A total brew time is the sum of things that differ from one kitchen to the next: the brewer's shape, the thickness of the paper, the size of the dose, the grinder, how the water was poured. Double the recipe in the same brewer and the bed is deeper and the brew longer, with nothing wrong. A Chemex and a V60 given the same grind will not finish together.

So a time is useful in one way only: against your own last brew of the same recipe in the same brewer. If it took much longer, something made the bed more resistant; if it rushed, something made it less. That tells you a change landed. Whether the change was good is for the cup to say, and a brew that tastes right has taken the right time, whatever it was.

The tools that go with it

CoffeeHQ explanation

• Make my coffee better — Takes your brewer and what you noticed, and gives the possibilities, the quickest check and one change, pair by pair.
• Stronger, weaker or better brew assistant — Does the arithmetic of a ratio change from your own dose and water, and ranks the levers for a taste.
• Pour-over planner — Turns a dose and a ratio into a pouring schedule you can repeat, which is what makes a comparison fair.
• Grind size guide — Shows where each brewer's range sits and how large a step is worth making for it.
• Water suitability helper — For a cup that is flat with every coffee: reads your water's hardness and alkalinity for taste.

What this page leaves out

CoffeeHQ explanation

It gives no brew time, no water temperature and no number of pours as right. It does not rank brewers. It does not say that sour means too little was extracted or that bitter means too much: in the one panel study read, strength mattered at least as much as extraction to both, and that study was one coffee in one drip brewer.

Immersion brewers, where the coffee steeps in all of the water, behave differently and are covered on the French press and AeroPress pages.

What to do next

• Make my coffee better — Choose your brewer, tick what you noticed, and get the check and the one change for that pair.
• Extraction basics — Strength and extraction as two numbers, and what studies found about sour and bitter.
• Grinding and particle size — Why a grinder makes a distribution and not a size, and why a setting does not travel.
• Water chemistry and brewing — For a cup that is flat with every coffee: what alkalinity and hardness do.
• Tasting Lab — A place to record what you changed and what it did, kept in your own browser.
• Become a barista — A structured programme from dose and grind through milk, drinks and maintenance.