What are the characteristics on which coffee is judged?

Grind size is the one pour-over variable you cannot judge by eye, and it decides extraction yield and strength more than most brewers admit. Three practical checks work together: the passing rate through a No. 20 sieve, the flow rate and total extraction time, and the taste in the cup, adjusted backward until the brew lands where it should.

The other three variables, coffee-to-water ratio, extraction time, and water temperature, can be read directly off a scale or thermometer, so they are easier to repeat. Grind is different, which is why the article asks what are the characteristics on which coffee is judged? and answers with measurable references: sieve passing rates and grind targets for different roast levels.

Many coffee enthusiasts feel their brews never taste as good as what they get in a café, but the problem often lies in the grind size. Extraction yield and strength are affected by four factors: grind, ratio, time, and water temperature—and among these, only grind size cannot be precisely judged by the naked eye. To help everyone find the right grind coarseness, Front Street shares three practical methods: measuring the passing rate with a No. 20 sieve, observing the flow rate and extraction time, and working backward from taste to adjust direction. The article also gives specific grinding recommendations and passing rate references for beans of different roast levels, and retains Front Street's brewing parameters and product examples.

Many people brewing coffee at home feel the results are less than ideal, and Front Street repeatedly points out that the crux is usually the wrong grind size. What determines whether a pour-over tastes good is extraction yield and strength, and four variables can influence these two metrics: grind coarseness, coffee-to-water ratio, extraction time, and water temperature. Each variable affects the final extraction result, so to get a satisfying cup, you must match them with the right parameters.‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Among these four variables, only the grind size of the coffee grounds is invisible and intangible; the other three can be read directly. So when you use the same beans, the same brewing method, and seemingly identical parameters, yet the coffee tastes worse than the shop's, there's no need to overthink it—eight times out of ten, the grind size is off.‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Since the coarseness of the grounds can't be seen at a glance, most of the time we can only judge by sight and feel, and use references like fine sugar or coarse sugar as analogies. But this kind of description isn't rigorous, because the range is simply too broad—everyone's mental standard for sugar granule size is different, and the particle shape seen by the naked eye is only superficial. So how exactly can you accurately find the right grind size? Consider the three approaches Front Street introduces below.

Sieve Measurement Method‍

"A No. 20 sieve passing rate of such-and-such" is an indicator Front Street often mentions in articles; it is a value obtained by measuring coffee grounds with a No. 20 sieve. Compared with other methods, the sieve provides a more objective benchmark, and the margin of error when everyone compares is much smaller.‍‍‍‍‍‍

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Everyone uses different grinders and beans, so specific grind sizes can't be communicated by machine model and setting. Even with the same machine and the same setting, the coarseness produced can differ due to varying degrees of burr wear. The No. 20 sieve, however, can provide relatively reliable data; even if equipment and materials vary widely, you can use it to dial in a roughly equivalent grind size.

The No. 20 sieve has an aperture of 0.85 mm, and the sieve box is divided into upper and lower layers. The method is simple: take a certain amount of coffee grounds and put them into the sieve, then start shaking!! Shake until no more powder passes through the sieve.

Then simply weigh the grounds that passed through to get an intuitive result. For example, if Front Street puts in 10g of coffee grounds and 7g pass through the sieve, then the passing rate of this batch is 70%. If someone else wants to use the same grind size as you, they just need to adjust the grind until the passing rate reaches 70%. No matter what machine or what beans, this standard applies universally.

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Coffee of different roast levels needs different coarseness. Light to medium roast beans have a shorter heating time and a harder texture, so the grind must be finer to increase the surface area in contact with water and release more floral and fruity compounds. For example, Front Street. Fruit Dingding, Front Street. Sun-Dried Huakui, and Front Street. Huahudie are all suited to a fine-sugar-like grind, corresponding to an 80% passing rate on a No. 20 sieve.

For medium to dark roasts, the heating time is longer, caramelized substances are more abundant, and the internal structure is looser, so sweet and bitter components are released more easily when they meet hot water. Therefore, grind to coarse-sugar granules, corresponding to a 70–75% passing rate on a No. 20 sieve—for example, Front Street. Mandheling with nutty and spicy flavors, Front Street. Queen's Manor Brazil with a pronounced roasted peanut aroma, and Front Street. Bird of Paradise with a toasted bread note.

Below is the grind size Front Street uses for pour-over, for your reference: hot brew coffee is ground to an 80% passing rate on a No. 20 sieve, while iced brew coffee is 85% on a No. 20 sieve.

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However, the sieve method also has shortcomings: it can only distinguish particles larger or smaller than 0.85 mm. In the article "How Much Does Coffee Bean Grinding Affect Extraction?", Front Street specifically mentions that due to grinding characteristics, the particle sizes produced are not uniform. Even the best grinder cannot achieve complete uniformity; it can only keep most of the grounds within a certain range of coarseness.

Below is a batch of Front Street Fruit Dingding coffee grounds ground by an Ek43

Front Street uses a sieve to separate them into large, medium, and small particles

So when the grinder is of average quality, or the burrs have become dull, the grounds produced will be very uneven. Even if the passing rate value is the same as someone else's, the taste may differ greatly. In this situation, Front Street would suggest switching to the other two methods to judge grind size.

Flow Rate and Extraction Time

The coarseness and uniformity of coffee grounds affect the flow rate during brewing: the coarser the grounds, the faster the water flows; the finer the grounds, the slower the water flows. The flow rate in turn relates to how long water and grounds stay in contact—the longer the extraction time, the higher the extraction yield, and vice versa. Therefore, with all other parameters locked in, we can infer the grind coarseness from the speed of the flow.‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Take Front Street as an example: brewing a pot of light roast coffee with 15g of grounds, water at 92°C, and a 1:15 ratio, the time will fall between 2 minutes and 2 minutes 30 seconds. If the final brewed coffee exceeds this range, the grind must be adjusted accordingly. Because all parameters are fixed, only the grind can change the extraction time. If the flow is too fast, make the grind finer; if the flow is too slow, make the grind coarser—it's that simple~‍

Of course, judging whether a cup of coffee is good based solely on extraction time isn't entirely reliable, so it needs to be combined with the third situation to assess: taste.‍‍‍‍

Taste

As Front Street said at the beginning, extraction yield is crucial to a cup of coffee—it represents how much of the coffee has been dissolved out. These components are the source of coffee's flavor, and dissolving too much or too little will reduce the positive experience of a cup. Therefore, by tasting how the coffee performs, we can judge whether the grind needs to be made finer.‍‍‍‍‍

When too little material is dissolved, that's what we call under-extraction. Because there isn't enough sweetness and bitterness to balance the acidity, the coffee will taste rather sharply acidic; moreover, the mouthfeel will seem very thin due to the lack of substances, with almost no aftertaste. If you taste this in your coffee, then with the other parameters unchanged, you need to make the grind finer to increase the extraction yield.

Conversely, if the coffee tastes very full-bodied but carries obvious off-flavors and bitterness, it is likely over-extracted. In this case, if the other parameters remain unchanged, we can make the grind coarser to lower the extraction yield, so that the bitter and off-flavors don't dissolve too much.

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The above techniques are all based on a relatively stable grinder quality. If the grinder is too poor, or the burrs too dull, producing an excessive amount of fines that causes severe clogging during extraction, then it's best to switch to a different grinder. Of course, we can also adjust other parameters to achieve reasonable extraction, but that requires a deeper understanding of extraction theory. How to choose and how to adjust is up to you~ ‍‍‍‍‍‍‍‍‍‍‍

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