What Do Espresso Grinders Do? Tips for Adjusting Your Grinder

There is a metal box that sits on your counter that breaks coffee beans into teeny tiny pieces. Sometimes you move the dial right, other times left, and it changes the way your coffee tastes.

Are you curious to understand what your grinder does? Want some guidelines for adjusting your grind? Read on as we take a closer look at grinders and the act of "dialing-in".

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A Particular Grinder is Burr-y Good for Espresso

You may have heard the term “variance” before when speaking of grinders. This describes the variance of particle size in ground coffee. We want to avoid too much variance. Why?

Variance will cause inconsistency in quality. If we can control the size of grind particles, we can control more of the consistency of espresso.

A blade grinder chops beans up in varying sizes so it's grind variance is very high. This removes a level of quality control and may lead to weird tasting coffee. No one has the time to hand-pick the best particles in a grinder. This is where a burr grinder comes in.

What's a Burr?

A burr grinder is known for its consistency, uniformity of grind particles, and wide spectrum of sizes.

It features two abrasive plates, called burrs, that are stacked on top of each other and can move closer or farther apart depending on your settings.  Beans are fed into the burr set and ground with consistency before dropping out of the chute.

Since the beans are forced into such a small gap between the burr sets, there is no way for them to escape.

There are different types of burr sets: flat and conical burrs. Conical burrs are often quieter and quicker, relying one gravity to force beans down. They are cheaper and found in almost all home espresso grinders. Flat burrs, found mostly in commerical grinders, boast a better uniformity in grind size and less variance. Our home grinder, the Rocky, uses flat burrs for an extra level of consistency and cafe-quality reliability.

Grinders Modify Surface Area

When we turn our grinder’s dial, we are adjusting the fineness or coarseness of our coffee. The two burrs will move closer (for fine grind) or farther apart (for coarse grind). It is here that we are exposing more of less surface area. Now for a little extraction crash course.

We can only brew coffee that is ground. It accelerates the rate in which we can get to its solubles: dissolvable solids that make up the sugars, oils, and acids in coffee. The faster your brewing method is, the finer your coffee grind may need to be. It is all about balancing the time your coffee is in contact with brewing water and how much surface area you are exposing to the water.

Coarser grind sizes expose less surface area. Cold brew uses a coarse grind size because the coffee is in contact with water anywhere from 14 to 48 hours! A fine grind would expose too much surface area to water thus extracting too many solubles. This leaves us with a bitter that tastes more like molasses than iced coffee.

Fine grind is used for things like espresso and Aeropress, which uses pressure to help extract coffee. Since these brewing methods involve pressure and a shorter amount of time than cold brew or the 4-minute Mr. Coffee, we need a finer grind to get all those solubles in time!

If you were to use a coarse grind size in an espresso machine, your coffee would be flying out and hitting the wall behind you. There is not enough restriction between a coarse grind and 9 bars of pressure, thus water flows out fast without grabbing the sugars, oils, and acids we need for something delicious.

Times You Should Adjust Your Grind

Time is your best friend when deciding whether you should adjust your grind. A typical espresso is around 25-30 seconds. If your shots are coming out in 15 seconds, you will need to adjust your grind settings.

Let’s try to pull some of the information we covered into an example.

Your shots are now running 15 seconds when usually they brew for 26 seconds. Your shots taste great when they brew around 26 seconds. The 15-second shot tastes salty and doesn’t have a lot of flavor. What change to bring your coffee back to normal?

If you answered make your grind finer, you are correct! The time indicates that the grind size may be too coarse because of the speed of the brew time. By exposing more surface area and choosing a finer grind, we restrict the flow for a slower brew time to pull more sweetness.

Trust Your Tongue!

If something tastes “off” or icky, you are right in saying your espresso needs some tuning. A strong palate takes lots of practice and we all start at the same place. Using a grind resource to calibrate your tastebuds will help alongside note-taking and curiosity about dialing-in.

Overextraction: Tends to taste bitter, roasty, hollow. We were able to extract the acids and sugars in the coffee but they are now overshadowed by a large amount of other not-so-tasty solubles. In cases where the grind was way too fine, it can cause espresso to drip slowly and reach 40+ seconds of extraction and taste almost chemical and pungent!

Underextraction: Tends to taste salty, sour, and unpleasantly acidic! Think lemon juice. The coffee didn’t have enough contact time with the water to get to the sugars and oils that make espresso sweet and syrupy. Espresso that is underextracted due to coarse grind tends to appear a pastel yellow when coming out of the portafilter. This indicates only a small amount of solubles are being pulled because of the light color where a balanced espresso tends to look like strings of dark caramel as it brews.

It's In the Technique

Give dialing-in a shot and share your results with us on Instagram for a chance to be featured on our profile! Tag us at @Rancilio.USA