“Grind”, usually refers to the degree of fineness, or coarseness coffee is ground prior to brewing.
To make an informed decision about which grind is ideal for your brewing method, we must first understand the effect that grind levels have on the extraction process (brewing):
1. There is a direct relationship between degree of grind and the amount of time the coffee and the water are in direct contact for.
2. The finer the grind, the more surface area of the bean is exposed to the water. More exposed surface, means more soluble solids from the ground coffee are made available to be dissolved.
What does that mean to me at home?
The faster the brew method, the finer the grind!
If your brew method results in the coffee being in direct contact with the water for a long time, such as in a French-press, which requires 4-minutes for extraction, you would want to use a coarse grind to minimize the amount of surface area exposed to the water in order to limit the extraction.
On the other end of the scale, if the coffee and water are in contact for only a very short period of time, such as Espresso which requires only 20-30 seconds of extraction time, you would want to use a very fine grind to maximize the amount of surface area exposed to the water to facilitate rapid extraction.
Very Fine Grind – Espresso machine.
Fine Grind – Cone-shape filter machine.
Medium Grind – Flat-bottom shape filter machine.
Coarse Grind – French-press or Bodum brew method.
And a plethora of choices in-between these. 🙂
Further, Your choice of grinder may also drastically change or improve the results. There are two main types of grinders: Blade and Burr Grinders.
A blade grinder is simply a rapidly spinning blade on a motor, and your degree of grind is determined simply by how long you keep the grinder running, leaving you little control. However, it should be noted here that even grinding freshly before brewing with a blade grinder is better than buying ground coffee.
A burr grinder is far superior to a blade grinder, simply because it allows for precision and control in the grind degree:
Burrs are two discs with serrated “teeth” on the one flat side of each burr. Usually one burr will spin and the other will remain stationary. The grind degree is determined by how far apart the two burrs are positioned by the user, the closer together the finer the grind. This method of grinding results in the coffee being ground (or more accurately “shaved”) to a consistent size and shape, hence greatly improving consistent extraction as each grind will have roughly the same amount of surface area exposed to the water. Another kind of burr-grinder is a conical burr, that allows an even more consistent grind quality, but usually cost more.
It is important to maintain the serrated teeth on burr grinders to keep them sharp, or your grinder will simply end up crushing the coffee into little pebbles, suitable for skipping along the surface of the ocean, but not much else.
Grinding coffee also exposes a larger surface area of the bean to oxygen, light and moisture, meaning that grinding facilitates a more rapid departure of the CO2 in the bean which carry the aroma and flavour with it. About 4 minutes after grinding, the beans have lost a significant enough volume of CO2 into the air to drastically change the flavour profile of the cup. Hence, grinding coffee just prior to brewing is very important.