Grind Settings for Coffee Brewing
Some of the most common questions we get from our customers here at Café Altura are about coffee grinding, specifically, what grind setting to use when brewing. We’ve explored the concept of grind size distributions and the importance of a good grinder in a previous post, but today I’d like to dive a little deeper into the specifics of why using different grind sizes for different brewing methods matters. I’ll do this by engaging in two discussions in turn. First, I will give a brief primer on extraction theory, and describe the ways in which grind size plays into extraction. Second, I will provide an overview of two different brewing methods (pour-over drip brewing and espresso) and describe the specific grind settings they require and why. I will conclude by providing some recommendations for other brewing methods. In so doing, I hope to provide both practical information and theoretical under-grinding which will assist you in making the best cups of coffee possible at home.
Brewed coffee is, at its most basic level, a solution, or a substance created by using a solvent to extract and dissolve compounds from a solute. Water acts as a solvent, and roasted, ground coffee acts as the solute from which tasty compounds are being extracted. Though tastes vary, the goal of any coffee preparation is a well extracted cup of coffee of proper strength and dissolved solids concentration, free of off-flavors; an under-extracted cup will taste overly sour, an over extracted cup will taste bitter, and a properly extracted cup will taste just right in between those two poles. If you’d like some more information on precisely what proper strength and dissolved solids concentration looks like from a numeric perspective, you can find it on the Specialty Coffee Association’s website.
For our purposes, however, we’re going to focus more on how the nuts and bolts of coffee prep affect flavor, working with the well-founded assumption that good preparation practices and brewing ratios lead to tasty extractions of proper strength and concentration. Lots of factors play into coffee preparation and extraction, including water temperature, rate of agitation, and water composition, but most salient to our discussion is grind size, or the average size of the coffee particles with which the water is interacting.
Grind size is important because of how it affects a coffee’s surface area. When coffee is ground, the surface area of the beans rapidly expands; countless small particles of ground coffee succeed the large, smooth surfaces of coffee beans. This increase in surface area allows for water to more easily extract the compounds in a coffee; there is simply more space for the water to physically access the coffee than there was before. This means that the finer that a coffee is ground, the larger its surface area, which in turn, leads to a higher potential extraction yield. Conversely, the coarser a coffee is ground, the less area there is for the water to extract from, which means a lower extraction yield potential.
Practically speaking, this matters in coffee brewing because water does not interact with coffee in the same manner in every brewing method. Espresso machines use pressure, drip coffee uses gravity, and a French press strains coffee steeping in water. Each brewing methods idiosyncrasies are what make the flavor profiles they offer unique and interesting, and to properly leverage these peculiar attributes to achieve delicious flavors, method-specific grind settings are required.
Brewing Method Specific Grind Sizes
Now that I’ve established a basic understanding of coffee extraction and the important ways in which grind size factors into it, I’d like to explore two case studies in brew method specific grinding in turn; pour-over drip coffee and espresso.
Pour-over drip coffee is one of the simplest and most common methods of coffee brewing; hot water distributed over ground coffee to produce a delicious beverage. The downward pull of gravity is what causes water to be drawn through the coffee grounds, but the rate at which that draw down occurs is determined by the grind size of the coffee; water flows slowly through finely ground coffee, and quickly through coarsely ground coffee. Because a brew cycle of around three and a half minutes tends to produce proper extractions for pour overs, a proper grind setting, then, is one which causes the brew to occur in this time frame. In general, this means a medium-fine grind, around the consistency of table salt. A grind setting at around this consistency will ensure that the water has enough time in contact with the coffee to extract the delicious flavors contained therein. Finer, and the coffee will spend too much time in contact with the water, causing over-extraction and bitter flavors; coarser, and the coffee will not spend enough time in contact with the water, causing under-extraction and sour flavors.
Espresso is not a common fixture of home coffee brewing, but is very prevalent in café culture; lattes and cappuccinos are staples of coffeehouses the world over. The reason for this discrepancy is that espresso is a very finicky coffee preparation method, largely due to its use of pressure in the brewing process. This potential preparatory pitfall is also what makes espresso so unique; by using pressure generated by a pump, espresso machines produce a viscous, highly concentrated coffee extraction which has a much more compressed and intense flavor profile than drip brewed coffee. The use of pressure also causes the extraction to occur very fast relative to drip coffee, with brew times in the range of 25-35 seconds producing around an ounce and a half of liquid.
To achieve such extreme extraction benchmarks, a markedly different grind setting than that used for drip coffee is required. In lieu of the more moderate medium-fine setting which allows water to drip through coffee at a moderate rate, espresso substitutes a very fine grind setting to create resistance to the pressurized flow of water and ensure that extraction occurs in the appropriate time frame determined for that coffee. If one were to use a drip coffee grind setting in an espresso machine, the pressurized water would shoot through the coffee extremely fast, severely under-extracting the coffee and causing unpalatable sourness. However, if the coffee is too fine, the pressurized water will flow through the coffee very slowly, causing a bitter, over-extracted shot. Because they use pressure to brew, espresso machines are extremely sensitive to changes in grind size, and baristas must constantly monitor and change grind settings to achieve proper extraction parameters. This process of calibrating grind settings to the machine to extract coffee properly is known as “dialing in a shot.” Because the grind setting needed to achieve proper extraction parameters is so variable, dialing in is a crucial element of espresso coffee brewing.
Grind Setting Recommendations
To conclude, I’d like to offer some general grind setting recommendations for common brewing methods. These settings are just suggestions; always experiment and try new methods of brewing to see what fits your taste.
Feel free to comment or reach out if you have more grind size questions (we’re always happy to talk coffee), and be sure to check this blog often for more discussion of all things coffee. Until next time.
Article By : Bret Colman, Director of Coffee / Head Roaster, Cafe Altura Organic Coffee