What Is Coffee Grind Size?
Grind size is an important factor in coffee preparation, and it refers to the how fine or coarse the coffee bean is ground in order to prepare the coffee beverage.
What Is the Coffee Grind Size for the Major Brewing Methods?
In general, each coffee brewing method has its own grind size range, specific to the extraction parameters. For some methods, the grind size and consistency are very important, while for others not critical, but still important.
The universally accepted standards for grind size are the following:
- Turkish Coffee, (Greek Coffee) – the finest grind, powder, (flour).
- Espresso – second finest, (table salt).
- Drip coffee – medium-fine to medium and medium-coarse. This includes pour-over drip, immersion drip, and automatic drip coffee makers.
- French press, percolator, cold brew – coarse grind size.
How does the Grind of Coffee Affect Extraction Rate?
The coffee extraction rate increases with a larger contact area. Finer ground coffee has more surface area, hence a higher extraction rate. This translates to a higher concentration, (stronger coffee). The brewing parameters also need to be adjusted accordingly. With a higher extraction rate, we need less brewing time. At the same time, a finer grind will reduce the flow rate and as a result, the contact time.
How does the Grind Affect the Taste of Coffee?
Considering the extraction rate, coffee can be under-extracted, if the grind size is too coarse, and it will taste sour, underdeveloped and weak. Coffee will be over extracted if we grind too fine, and it could taste bitter and too strong.
What Is Grind Size Consistency and How it Affects the Extraction
Grind size consistency is an important factor during coffee preparation and it refers to the uniformity of the particles size after the beans have been ground. Ideally, all grounds should of an equal size after milled.
The grind size consistency affects the extraction. If the coffee grounds are not uniformly ground, the extraction rate will be different for the various particle sizes. A small coffee particle will extract faster than a larger one. As a result, we could have part of the coffee under-extracted, (the coarser bits), and part of the grounds over-extracted. (the fines).
Coffee Grinder Types
The type and the quality of a coffee grinder will affect the grind size consistency. Coffee grinders can be categorized as follows:
- Blade Grinders, (chopping)
- Burr Grinders, (crushing)
- Mortar and Pestle, (pounding)
- Roller grinders, (roller grinding)
Roller grinders are mostly used for industrial applications, where large quantities of coffee are ground. They offer the best consistency, but they are very expensive and they are not affordable for small-scale applications.
Blade grinders are by design poor from a consistency perspective. They chop the bean with every pass, in a random sequence. We cannot achieve a uniform grind size by using a blade grinder. In theory, the longer we grind the beans, the more chances we have to chop all of the bits in the grinding chamber. From this perspective, we can obtain a decent dose for a Turkish coffee, because we can repeat the milling until all the bits are turned into powder. A blade grinder is, however, not recommended for any other coffee brewing method.
Bur coffee grinders are best suited for home use and for coffee shops, and they can be categorized as:
- manual grinders and
- electrical grinders
Manual grinders are suitable for personal use when a small quantity of beans is required. The biggest advantage of manual grinders is the low grinding speed and the independence from electricity.
Electrical grinders are more popular because of the convenience. A variety of models exist on the market, the differences being: the grinding speed, the motor’s power, the burrs size, and the burrs shape. From this perspective we can distinguish:
- flat, or disc burr grinders and
- conical burr grinders
For both types, one disk is stationary, and the other disc is turned by an electric motor. Disc burrs are two discs with grooves machined into them. Conical burrs are two cones with the grooves cut in the inside of the large cone and on the outside of the small cone. In both cases the sharp edges of the grooves pass at a small distance to each other, cutting the beans. The distance between the cones can be adjusted so that the particle size can be modified.
There is some discussion about the difference between the conical and flat burr grinders. Some people think there is a slight difference in how coffee extracts. However, the only significant factor, from this perspective, is the burrs size and not the shape. The larger the burrs the better the consistency. Another important factor is the grind size adjustment mechanism. A step adjustment can offer a number of predefined grind size settings, which are often good enough for the typical home barista. A stepless adjustment type has an infinite number of grind size settings, and espresso lovers prefer these because they offer more precision.