Roasted coffee beans must be grinded to break the beans into smaller pieces so as to increase the surface area necessary for extraction. The finer the grind size, the faster is the extraction, and vice versa. Depending on the brewing method/equipment, the right size must be adopted so that the rate of extraction is ideal and less sediments go into the cup. Due to oxidation that will stale the coffee grounds as soon as the beans are grinded, it is always recommended to grind the coffee beans just before brewing and with the right amount. So what are the different types of grinders? Burr and blade grinders.
To start with, blade grinder is the cheapest and the most straight forward coffee grinder commonly found in most shopping malls. Equipped with a motor and a blade, user just have to throw in the beans, cover the grinder and press the power button. The grinding blade will rotate, whack through the beans and break them into small pieces. The grind size depends on the duration of the grind, that is, a finer grind is achieved by leaving the grinder on for a few more seconds. A very simple process, but the weakness is the lack of control and consistency of the grind size. Regardless of the duration of the grind, the grounds will contain sizes ranging from powder to chunks. The difference is just the quantity of these sizes.
Next is the burr grinder. There are 2 types of burr grinders: flat blade and conical. The conical burr grinder has 2 cone shaped burrs facing each other at a distance that determine the grind size. Coffee beans are fed between them and crushed into uniform grind particles when one of the burrs rotates while the other is stationary. The flat blade grinder also comes with 2 flat and parallel blade burrs that provide shearing effect on the coffee beans, thus achieving uniform and larger surface area for extraction.
So the choice between blade and burr grinders is obvious: always go for the burr grinders. The next selection criteria is on the different types of burr grinders. Burr grinders can be further categorized based on the speed, dosing capability and the type of grind adjustment available. In terms of speed, there are (direct drive) high speed, gear-reduction low speed and direct-drive low speed grinders. The entry level to burr grinders is the high speed direct drive grinder whereby the high speed motor is connected directly to the burrs. Though high speed, it give rise to heat that affects the quality of the end grounds, noise that is not so pleasing to the ears, and the static that will lump the grounds into chunks that can adversely affects the packing of the coffee cake in the portafilter when making espresso. Nevertheless, with these disadvantages, these grinders will still do its job into producing uniform grinds at a low price point.
The gear-reduction low speed and direct-drive low speed grinders are the best grinders around and commonly used in commercial setups (such as cafes) and at home of coffee enthusiasts. They offer little or no static, much lesser or no heat and quiet operation, all these owing to the low RPM (revolution per minute) of the grinder burr. The gear-reduction low speed grinder has a high speed motor connected to the burrs via a set of gears to reduce the speed and maintain the grinding power. The weakness, as expected, is the noisier grind as compared to the direct-drive low speed grinders. So, if budget permits, go for the direct-drive low speed grinders such that the La Scala MC4 or the Rancilio Rocky, available on The QARR Shop.
Next in the selection of burr grinder is the choice between doser and doserless grinder. Dosers are designed to handle the volume of coffee in a commercial setup by allowing the barista to grind the beans in batches into a doser container that usually can hold up to around 6 dosages of grounds. A pull on the handle provided will dispense a single dose of grounds. Unless you are having a coffee party, most of the time you will only make one or couple of cups that do not warrant the need of a doser that inadvertently result in wastage of un-use grounds, staling of grounds, and additional parts for cleaning after usage.
Advocates of doser will explain that the doser will resolve the static problem created by the grinder, but the need for freshly grind coffee in small quantity outweighs this problem. And the static problem can be easily taken care of if you use a direct-drive low speed grinder. Personally, I will strongly recommend home user to go for the doserless grinder.
Finally, on the types of grind size adjustment, there are the stepped and the stepless adjustment grinders. Stepless means that you can have an infinite number of settings in terms of grind sizes. There is no preset stops where the grind setting will stop at, as compared to the stepped adjustment grinder. The choice here is subjective and individual, whether you need a guide in terms of the stepped adjustment or you are very particular about the slightest adjustment of the grind size. By the way, having stepped adjustment does not mean that there is very limited number of steps or adjustments available. Some very good stepped grinders provides more than 50 steps, which in most cases are more than sufficient to satisfy even for the most finicky coffee lovers in terms of grind controls.
So the verdict is to go for a doserless, direct-drive low speed burr grinder. As explained earlier, having a good grinder is the key to consistent and quality brew, every cup.