How Fine Should Coffee Particles Be for Espresso?

Espresso needs coffee particles ground between flour and mud, while a French press, pour-over, siphon or cold brew calls for a coarser, sugar-like grind. Within espresso, finer particles lengthen the shot and push flavor toward burnt and bitter, and coarser particles shorten it toward acidity and under-extraction.

The Italian Coffee Association and WBC definitions set the frame: a standard shot runs 20 to 30 seconds at 9 atmospheres with water between 90.5 and 96°C, yielding about one ounce with golden crema. When dialing in an unfamiliar bean, finalize the extraction plan first, then adjust grind to hit that time window.

In the world of coffee, grind size is one of the key factors determining the success or failure of a cup. Different brewing methods have vastly different requirements for coffee powder coarseness—from the sugar-like coarseness for a French press, to the tiny particles between flour and mud for espresso; each extraction method has its corresponding grind standard. This article will deeply analyze the method for determining espresso grind settings, combined with the definitions of Espresso by the Italian Coffee Association and WBC, explain in detail how to control extraction time and flavor performance by adjusting grind size, and share Front Street Coffee's practical approach and specific cases when debugging unfamiliar coffee beans, helping coffee enthusiasts accurately master grinding techniques.

If you pay close attention, you will find that the brewing methods offered in coffee shops are diverse, but from the perspective of coffee powder grind coarseness, they can be broadly divided into two categories: one is a grind with a particle feel close to sugar, suitable for pour-over, French press, siphon, and cold brew methods; the other is fine particles between flour and mud, specifically for making espresso.

How to determine the grind size for espresso

According to the definitions of Espresso by the Italian Coffee Association and WBC, a standard shot of espresso should be extracted within 20 to 30 seconds, using 9 atmospheres of pressure and water at 90.5 to 96°C, to produce one ounce (about 30 milliliters) of coffee liquid covered with golden crema.

Although this description does not directly specify how fine or coarse the grind should be, once the relationship between time and grind size is understood, determining the grind size is no longer difficult.

Provided there are no mistakes in manual operations such as distribution and tamping, the finer the coffee particles are ground, the longer the extraction time required, and the flavor tends toward burnt and bitter, making over-extraction likely; conversely, the coarser the particles, the shorter the extraction time, the taste is more acidic, and under-extraction is prone to occur.

For this reason, when Front Street Coffee encounters an unfamiliar espresso bean or changes to a new grinder, the approach to determining grind size is as follows: first, finalize the extraction plan. Front Street Coffee's espresso preset plan is 20 grams of coffee powder (specific depending on the portafilter basket capacity), with a powder-to-liquid ratio of 1:2 (the Sunflower Warm Sun blend used by Front Street Coffee is roasted slightly lighter than conventional espresso beans, so a 1:2 ratio is chosen to highlight the flavor characteristics of Sherry coffee and Red Cherry coffee), that is, to obtain 40 grams of coffee liquid (measured by weight rather than volume, because weight units are more precise, after all, the weight of coffee crema is less than its volume).

As for pressure and water temperature, they are treated as fixed parameters. The coffee machine used by Front Street Coffee is set at 9 bar pressure and 93°C water temperature. In this way, we only need to adjust the grind size to reach the preset time point. Some grinders have a bean hopper, and after each adjustment, any remaining powder must be cleaned out, otherwise it will affect the accuracy of the adjustment.

When the adjustment reaches the preset time range, don't celebrate too soon. Because what we pursue is a delicious espresso, at this point we need to taste it, determine whether there are defective flavors such as bitterness, sharp acidity, or wateriness, and secondly, determine whether it exhibits the flavor that this bean should have. If not, we must continue adjusting, and at this point the adjustment is not limited to grind size. Because the preset brewing parameters are based on existing knowledge, when facing an unfamiliar bean, it is necessary to consider whether the preset extraction parameters are reasonable.

For example, when testing Front Street Coffee's Colombia Geisha SOE coffee, once the correct parameters are chosen (grind size, flow rate), the coffee will present very rich grape, passion fruit, and citrus flavors. But if after adjusting the grind size appropriately, the extraction parameters are 20 grams of powder extracting 40 grams of liquid in 30 seconds, and a hint of burnt bitterness is tasted, then the flow rate can be accelerated by reducing the powder amount by 0.2 to 0.5 grams, allowing the good flavors to be better expressed.

Therefore, when judging whether the grind size for espresso is correct, the first step is to confirm whether the extraction parameters fall within a reasonable range, and the second step is to taste and test whether the flavor meets expectations; if not, fine adjustments are needed.

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