Grinder Basics

By Chase Lemos, Nuova Ricambi USA

We have all gone into our favorite coffee shop and been amazed with the coffee quality we are presented. The question is – how do they do it?

The answer is simple – they have all the right tools. They use high quality beans high quality coffee brewing tools (be it an espresso machine, coffee brewer, drip setup, etc.) and a high-quality grinder to break down the coffee beans right before making your drink.

Few people realize the impact that a coffee grinder has on overall coffee flavor, yet it has a huge effect on how coffee tastes. The reason a coffee grinder is so important lies in the very reason that a grinder is needed at all – the need to break down the bean to expose the interior to hot water, allowing the oils and flavors to be extracted. Fine ground coffee creates an increased surface area causing greater dissolution of oils in the drink. More exposed surface area means more water molecules can ‘rip’ the coffee oils out of the bean and bring them along into the cup. Inversely, a coarser grind, means less exposed surface area and decreased dissolution of oils. It is very important to match grind size with brew method to balance extraction. More of that later.

Roasted coffee in the bag is always exposed to air (some roasters use airtight bags and nitrogen flush the bags to remove all air particles, but the following effect will be the same once the bag is opened for the first time). The oxygen will begin to act on the coffee, breaking apart the oils thus aging the coffee and flattening out the flavor. Pre-ground coffee will have more exposed surface area to air which speeds up the denaturing process. This is why pre-ground coffee has a shorter shelf life than whole bean coffee.

Given the importance of the size of coffee grounds used for making coffee, it follows that inconsistent grind size will make determining the right grind to use for extraction very difficult. Thus, a good coffee grinder is adjustable to the brew method and is consistent when breaking apart the coffee bean allowing for even extraction of all particles.

There are two main types of grinders used in the coffee industry: the blade grinder and the burr grinder.

The blade grinder has several advantages. It is cheap, small, fast, and easy to operate. The trouble with a blade grinder is that they produce a wide range of particle sizes with every dose of coffee ground which makes them inaccurate in terms of achieving a consistent grind size. They don’t allow for any portion control, and have tend to overheat the coffee. All these characteristics can lead to inconsistent extraction and flavor in the cup.

Burr grinders, on the other hand, do a very good job of grinding coffee evenly, allow for a broad adjustment range and preserve the natural coffee flavor. However, they tend to be louder, slower and more expensive than blade grinders. There are three types of burr grinders: bulk grinders, flat burr grinders, and conical burr grinders.

Bulk grinders are very good at quickly grinding a large amount of coffee into relatively even pieces. They are used to grind pre-ground coffee and to grind coffee before it goes into a commercial coffee brewer. They are adjustable and can achieve numerous grind sizes for brewing coffee, dripping coffee or percolating coffee, but are not considered to be sufficient to grind coffee fine enough for espresso.

Flat burr grinders are generally, though not always, found on espresso grinders for home use to medium cafe size. They are less expensive than conical burr grinders, have a higher rotation speed (creating more heat and requiring more time to cool) and can be louder and messier (due to the increased rotation speed). Flat burr grinders do a great job creating coffee ground for espresso and can excel in the twenty drinks an hour or less range.

Conical burr grinders, on the other hand, can cost more, have a lower burr rotation speed which makes them quieter with less ‘throwing’ of the coffee. Conical burr grinders are generally preferred for high volume cafes because the bulkier conical burrs have more mass and will take more energy to heat up. There are many more nuances such as burr metal composition, burr sharpness, burr tooth shape and many, many other factors that grinder manufacturers manipulate to allow their grinder to perform the way they want it to.

Breaking down a whole coffee bean into parts is deceptively simple. While breaking down the bean, it is critical to take into consideration grind size, grind consistency and repeatability to ensure that you are brewing that cafe level cup of coffee.

Optimal Grind Settings for Common Brewing Methods

  • French Press requires a coarse grind - the beans should still be in distinct chunks. You can afford to have a less exposed surface area because your coffee will have the added benefit of time in the water.
  • A Siphon Pot requires a medium-coarse grind. The pieces of bean should begin to all blur together. The coffee will have less time to sit in the water than a French press but will have more time than a traditional pour-over method
  • A Chemex requires a medium grind. The grinds should be well mixed together in a coarse powder. This method uses a thicker paper filter than a traditional pour over method which slows the coffee’s passage through the grounds.
  • A Pour-Over or Aeropress will take a medium-fine grind. The powder should be indistinct pieces, though far coarser than a flour-like consistency. The water will flow over the coffee with only the grinds slowing it down
  • Espresso requires a fine grind. The powder should be approaching flour in consistency. It should feel silky to the touch. When packed together, it should retain its form. The coffee will be packed together tightly enough to prevent nine bars of pressurized water from passing easily through the puck
  • Turkish coffee requires a very fine grind. The coffee should be flour-like in consistency. The coffee will be dissolved in hot water and will be ground fine enough for the particles to be suspended in water.