How does deep roast coffee change your pour-over ratio?

Pour-over brewing uses two parallel ratio systems: the coffee-to-water ratio, measured with a digital scale, and the coffee-to-beverage ratio, read from server markings. Because saturated grounds absorb roughly twice their weight in water, a 1:15 coffee-to-water ratio equals about a 1:13 coffee-to-beverage ratio.

The beverage ratio offers more flexibility when handling filter basket clogging or deep roast coffee foam, while the water ratio gives precise segmented pouring data. Classic servers such as the Kono and Hario Cloud hide scale lines: a 600ml Kono marks 2-cup (240ml) and 4-cup (480ml) points, which explains its 12g, 24g and 36g doses.

In the parameter system of pour-over coffee, the coffee-to-water ratio and the coffee-to-beverage ratio are two parallel measurement logics. The former relies on a digital scale to precisely control the amount of water poured, while the latter determines the final coffee liquid volume through the markings on a server. Many classic utensils, such as the Kono server and the Hario Cloud server, have hidden scale markings that correspond to specific coffee dose designs. The coffee-to-beverage ratio is more flexible when dealing with filter basket clogging or deep-roast foam handling, while the coffee-to-water ratio excels in the precision of segmented pouring information. The two can also be converted into each other: coffee grounds absorb approximately twice their own weight in water when saturated, so a coffee-to-water ratio of 1:15 roughly equals a coffee-to-beverage ratio of 1:13. Only by understanding this logic can you make reasonable adjustments based on different beans and utensils.

If there is no scientific coffee-to-water ratio as a reference when brewing coffee, it is basically equivalent to doing it by feel. How many grams of coffee grounds to use and how much water to pour accordingly—a digital scale has now become almost standard equipment in the pour-over process.

However, besides the coffee-to-water ratio, there is another easily confused parameter called the coffee-to-beverage ratio. The coffee-to-beverage ratio describes the ratio between coffee grounds and the final coffee liquid obtained. In other words, it is how much coffee liquid is brewed from a certain amount of grounds.

Why do two different calculation logics exist? In the early days, digital scales were not as compact and precise as they are now, and it was almost impossible to accurately know how much water had been poured. As a fallback, people used the size or scale lines of containers to estimate an approximate ratio.

Take the Kono server as an example. On the surface it seems to have no scale markings, but in fact it has inconspicuous marks. On a standard 600ml Kono server, two lines are engraved, corresponding to 2 cups and 4 cups respectively. Kono defines one cup of coffee grounds as 120ml, so the 2-cup line is 240ml and the 4-cup line is 480ml. This also explains why, when using Kono utensils, the coffee dose is often set to seemingly awkward values such as 12g, 24g, and 36g.

The Hario Cloud server also has inconspicuous scale markings. For the 01 server, the 300ml mark is located between the words "APPROX" and "300", while the 200ml mark falls at the boundary between the first and second layers of the cloud pattern.

In addition, measuring cups are also common tools, and they clearly indicate capacity graduations.

Is the data from the coffee-to-beverage ratio reliable? When discussing the coffee-to-water ratio, as long as both the coffee dose and water amount values are accurate, the result should not deviate much in theory, and the feedback from the digital scale is precise enough. But the coffee-to-beverage ratio, obtained by reading scale markings with the naked eye, can produce an error of about 10ml due to the viewing angle; if the table itself is not level, the error will be further amplified.

The coffee-to-water ratio has another advantage that the coffee-to-beverage ratio does not have: it can accurately record the specific amount of water in each pouring stage, making the information more detailed and controllable.

The coffee-to-beverage ratio also has an advantage that the coffee-to-water ratio cannot match, which is greater room for adjustment. For example, when the filter basket becomes clogged, you can boldly pour in a large amount of water to make the coffee bed tumble and stratify. You only need to watch the coffee liquid in the server reach the target amount and then remove the filter basket, without worrying about how much water is still left in it.

Some Japanese brewing schools advocate that the foam on the surface of the coffee is the source of bitter and off-flavors (for dark-roasted beans, in the era of flannel filter cloth). If measured by the coffee-to-water ratio, all the water must pass through the filter basket and fall into the server, and the bitter and off-flavor substances in the foam will also enter the coffee liquid. Therefore, they prefer the coffee-to-beverage ratio, and in the final step they often raise the coffee bed to prevent the foam from falling into the server.

The coffee-to-beverage ratio and the coffee-to-water ratio can actually be freely converted. The difference between the two lies in whether the water absorbed by the coffee grounds is counted. Assuming that coffee grounds absorb twice their own weight in water when saturated, a coffee-to-water ratio of 1:15 is roughly equivalent to a coffee-to-beverage ratio of 1:13.

The above content is compiled by CoffeeHunters, a coffee news website.