The Effect of Grind Size
Whenever you divide an object in half, the mass of the object stays the same but the surface area increases. In our case of the coffee bean, as you divide the bean into smaller and smaller pieces, you are greatly increasing the area of the bean that will be in contact with water during the brewing process, and also increasing the extraction rate of the bean, meaning smaller pieces need less contact time with the water. So the general rule regarding coffee grind size is this:
There are other variables that affect the extraction rate of the coffee, temperature being one, but by far and large grind size is utmost importance. We have developed the following chart to assist you in determining best grind for your preferred brewing method.