While many factors contribute to a coffee’s overall flavour—such as coffee variety, cultivation methods, post-harvest processing, storage, and roasting—brewing is a critical step in crafting a great cup at home. In fact, brewing has such a significant impact that even with the same coffee and method, small adjustments can change a cup from unremarkable to extraordinary or transform it from fruity and tea-like to earthy and roasty.

As a consumer, you play a pivotal role in this final stage of the coffee journey. This blog post explores key brewing variables, focusing on the pour-over method, and includes recipes using the Kelloo Ethiopian coffee roasted to a medium light intensity. By understanding how these variables influence flavour, you can craft a cup that is perfectly tailored to your taste.

Key Terms to Understand

When adjusting your coffee recipe, there are three essential terms to consider:

• Brew Ratio: The ratio of ground coffee to water.

• Total Dissolved Solids (TDS): The strength of the brew, representing the fraction of soluble coffee solids in the liquid.

• Percent Extraction (PE): The percentage of soluble coffee solids removed from the grounds.

By tweaking these parameters, you can amplify different flavour attributes. With specialty coffee, understanding these factors can elevate your cup from good to exceptional, whether you aim for delicate fruit notes or a fuller-bodied, roasty profile.

The Brewing Control Chart

The Brewing Control Chart is a visual tool that helps correlate brewing parameters with perceived flavours. It plots TDS on the y-axis and PE on the x-axis, creating regions that map out different flavour profiles.

• Lower left: Light, delicate, and under-extracted.

• Upper right: Full-bodied, rich, and potentially over-extracted.

For more about this chart, visit the Specialty Coffee Association’s guide here. I am reluctant to re-use a figure here, but I feel it is important for you to see the result of the work by Guinard et al. to refine the traditional brew control chart that has been used for decades (not shown here but you can easily find it). I like their chart as it shows all the possibilities of flavours for the coffee that they used in their study.

Measuring TDS and PE

To estimate TDS, I used a handheld refractometer that measures Brix. Converting Brix to TDS involves multiplying by 0.85. Degrees Brix (symbol °Bx) is the sugar content of an aqueous solution. One degree Brix is 1 gram of sucrose in 100 grams of solution and represents the strength of the solution as percentage by mass (source; for further information, see https://www.rdworldonline.com/what-are-brix-refractometers/). PE can then be calculated using:

PE=(Brix×0.85)×Mbrew/Mgrounds

Where Mbrew​ is the mass of the brewed coffee and Mgrounds is the mass of the coffee grounds. Both TDS and PE are percentages. We measure the mass of the brew because an amount of water that is approximately twice the mass of the grounds is retained in the coffee bed in the paper filter. It is the volume of the brew in which we have measured TDS.

While precise measurements help refine recipes, you can achieve excellent results by simply adjusting brew ratio and grind size. Grinding finer using agitation etc. can increase TDS and hence PE through its relationship shown in the equation above; increasing the amount of water increases PE by increasing the value of Mbrew/Mgrounds.

Three Recipe Experiments

I brewed three cups of Kelloo Ethiopian coffee, varying grind size and water-to-coffee ratio, while keeping other factors constant. Here’s how they turned out:

Cup 1: A Light and Subtle Brew

• Coffee: 15 g medium-roasted Kelloo Ethiopian coffee

• Grind Size: 3.0 turns on a 1Zpresso J Ultra hand grinder (medium-coarse)

• Water: 240 ml (brew ratio 240 ml/15 g=16) at 93 °C, cooling during the pour, i.e., kettle not returned to the base to maintain a temperature of 93 °C

• Brew took 4 min 20 s in total, Mbrew 201 ml

• TDS: 1.1%, PE: 14.8%

• Flavours: Weak, woody, faint fruitiness of green apple and prune

• Comment: Under-extracted. Suitable for those preferring very light, subtle flavours.

Cup 2: Balanced and Fruity

• Coffee: 15 g medium-roasted Kelloo Ethiopian coffee

• Grind Size: 2.5 turns on a 1Zpresso J Ultra hand grinder (medium)

• Water: 240 ml (brew ratio 240 ml/15 g=16) at 93°C, cooling during the pour

• Brew took 6 min in total, Mbrew 204 ml

• TDS: 1.4%, PE: 21.9%

• Flavours: Peachy fruitiness, dark sugars

• Comment: A well-balanced, sweet cup (to my liking). It would appear here that by choosing a finer grind, TDS and PE were increased versus Cup 1 and the flavours were strikingly different. That is, the point within the brew control chart has moved from lower left to upper right.

Cup 3: Full-Bodied and Rich

• Coffee: 15 g medium-roasted Kelloo Ethiopian coffee

• Grind Size: 2.0 turns on a 1Zpresso J Ultra hand grinder (medium fine)

• Water: 255 ml (brew ratio 255 ml/15 g=17) at 93°C

• Brew took 6 min 45 s in total, Mbrew 219 ml

• TDS: 1.7%, PE: 23.9%

• Flavours: Thick body, molasses, black treacle, spices

• Comment: Full-bodied and indulgent, ideal for those who enjoy richer, darker profiles and a fuller body. Grind size was lowered further and the amount of water increased by 15 ml. The position now in the brew control chart is further to the upper right. (What I have not demonstrated here is a coffee positioned in the upper left. To achieve that, I would try making TDS high with a fine grind setting and using lower volumes of water to keep within the lower ranges of PE. I expect that to make this coffee rather sour, but Guinard’s chart suggests there is a narrow window for a berry-like cup if TDS is not too high.)

Note, all tastings were done at 10 min after starting the pour over to compensate for the differences in brew times. The perceived flavours will differ when replicating the method used here on a different coffee bean, and you will have to make your own adjustments to suit your taste. For example, I received a very expensive lightly roasted coffee from a roaster in Holland. The coffee could be described as a funky and sour (with an exclamation mark). The parameters I use for this coffee is very different to those for coffees I receive from others, which tend to be darker roasts with less funky sourness and fermentation notes. These are two extremes and with the former I may try to reduce the sourness (increase extraction), while the latter I am trying to reduce the bitterness (reduce extraction, somewhere towards the bottom left or left of the brew control chart). It is common for me to use up a portion of the coffee in order to adjust and establish a recipe.

Tailoring Recipes to Your Preference

This experiment demonstrates that a single coffee can deliver vastly different experiences depending on how it’s brewed. To adjust for your preferences:

• For delicate and fruity flavours: Aim for the lower-left of the control chart (lower coffee-to-water ratio [e.g., 75 g coffee/L], coarser grind).

• For richer, darker flavours: Target the upper-right (finer grind, higher water-to-coffee ratios [e.g., 55 g coffee/L).

You don’t need expensive tools like refractometers to explore these variations—scales and a willingness to experiment will do.

Final Thoughts

The brewing process is your opportunity to express creativity and taste preferences with specialty coffee. By understanding and manipulating key variables, you can make each cup of coffee a unique and satisfying experience.

Try these recipes, make adjustments, and enjoy the journey of exploring all that your coffee has to offer. Let your cup be a reflection of your taste and appreciation for the craft.

Enjoy brewing.

I include here a video by James Hoffman that shows how to brew a single cup using the V60 dripper. This adds a visual instruction on how to use the V60 to make a brew; you can combine the information above to tweak your recipes and achieve the most desirable cups for yourself.