Brew Ratio

Phenomenon

Every morning you scoop two spoonfuls of coffee and brew a big mug.

Some days it is just right; some days it is clearly too weak. Then you switch to a dark roast, and with the same two scoops it comes out weak almost every day.

You believe you do the same thing every morning. Do you?

Variables

The "amount" in a cup of coffee involves three numbers:

The brew ratio is usually written like "1:16": 1 gram of coffee to 16 grams of brew water. Notice the beverage is less than the brew water, because the grounds hold on to some water, which stays behind in the brewer.

A scoop fixes volume, not weight.

Experiment

A thought experiment: same coffee, same grind, same pour-over technique, three cups:

1. 15 g coffee, 250 g water;
2. 15 g coffee, 300 g water;
3. 18 g coffee, 250 g water.

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Rank them from strongest to weakest. Which two will be closest in character — leaning sour or leaning bitter?

Your prediction

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One more: with the same spoon, take two scoops of a light roast and two scoops of a dark roast and weigh them.

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Do they weigh the same? If not, which is lighter?

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Observation

From strongest to weakest: 18 g with 250 g, then 15 g with 250 g, then 15 g with 300 g.

Changing the ratio changes strength the most; the character of the cup usually only shifts slightly — much less than when you change the grind Confidence: [Rule of Thumb]. It shifts at all because in a pour-over, more coffee means a deeper bed and slower flow, so extraction changes a little too.

Two scoops of dark roast usually weigh less than two scoops of light roast. The darker the roast, the more the bean expands and the more water and material it loses, so the same volume weighs less Confidence: [Established Mechanism]. That is why the dark roast at the start was "always weak": you thought you used the same amount, but you used less.

Model

Where strength comes from

Borrow two ideas the next chapter covers in depth: extraction is how much of the grounds the water took away, and extraction yield is that amount as a share of the dose; strength is how concentrated the cup is. They are related simply:

Dissolved coffee in the cup = dose × extraction yield

Strength = dissolved coffee in the cup ÷ beverage

So there are two ways to make a cup stronger:

• More coffee, or less water — changes the ratio; the character barely moves;
• More extraction — strength rises a bit, but the flavor moves toward bitter and drying.

The ratio is the main dial for strength. Extraction is a secondary dial, and it drags the flavor along with it.

Adding water after brewing is not the same as brewing with more water

Adding hot water to the cup after brewing changes only strength; extraction is untouched — what was taken from the grounds, and in what proportions, stays the same. Chapter 23 lets you taste this for yourself.

Brewing with more water is different: more fresh water passes through the bed, and the less dissolved material water already holds, the more it can keep dissolving Confidence: [Established Mechanism], so extraction rises a little. To make the same cup a bit weaker, diluting afterwards is usually more predictable than changing the brew water.

The water the grounds keep

Coffee grounds hold on to some water — roughly twice their own weight Confidence: [Rule of Thumb]. With 15 g of coffee and 250 g of water, only about 220 g ends up in the cup. When converting someone else's recipe, check whether they mean brew water or beverage.

"Just right" strength is a preference

Most common pour-over recipes fall between 1:15 and 1:17 Confidence: [Common Practice], which is a useful starting point. But how strong is right? Research found this is where people disagree the most Confidence: [Preference]. Strength has no right answer — only what you like.

Transfer

Write recipes as "dose + ratio", not "two scoops". Then scaling for a different mug or more people is simple multiplication.

A kitchen scale that reads to one gram is the best-value tool in this chapter.

Misconceptions

"Strong means well extracted." Strength is set mainly by the ratio. An intense, sour cup may well be under-extracted.

"There is a standard ratio." Common ratios are starting points. Strength is the most personal variable of all.

"Scoops are accurate enough." A scoop measures volume. Different roasts and grinds put different weights in the same scoop.

Real Lab

One way to do it: fix the dose, say 15 g, and brew three cups at 1:14, 1:16 and 1:18 with the same grind and technique. When tasting, first rank them by strength, then ask: apart from strength, how different is their character?

Check Your Model

Predict. You double both the dose and the water and brew one big batch in the same dripper. What happens to strength? Does anything else change?

Diagnose. A cup is balanced but too strong. A friend suggests grinding coarser. Why is that not the best first step?

Explain. In your own words: why can two cups be equally strong yet taste completely different?