Bad brew? How to read your coffee
When approaching a new coffee at home, we usually dive straight into a first recipe, whether it’s filter or espresso. Sometimes it’s a recipe we came up with ourselves, other times it’s a baseline suggested by the roaster.
The moment we taste that cup, we rarely enjoy it without overthinking and that’s our curse as coffee people. We immediately try to figure out: is the coffee any good? Did I brew it right?
When the result isn’t convincing, we tend to quickly “blame” one specific cause: the roast, the beans or the recipe. The reality is more complex: there’s much more to read in a cup before we can truly understand it. Coffee is a mosaic and learning how to interpret it is the key to improving as home brewers.
Key elements to consider
Age, origin, variety and processing method
Every coffee is unique. There is no such thing as “the taste of Guatemalan coffee.” Each region, variety and processing method develops distinct flavor profiles (unless we’re talking about trendy ultra-infused coffees, which often taste quite similar…).
The age of green coffee also impacts the cup: an “old crop” (think of more than 2 years from harvest) can taste flat and papery.
Roast style and degassing time
Every roaster has a philosophy and setup that affects solubility and flavor. Extreme roast defects are fairly easy to spot:
• Overroasted, often bitter, toasty, ashy.
• Underdeveloped, often grassy, sour, cereal-like.
Degassing time is crucial. As CO₂ escapes, the chemical balance shifts, affecting both extraction and flavor. Always consider your roaster’s suggested resting time and pay attention to how flavor changes over the days post-roast.
Water, the main ingredient
The minerals in the water (mainly calcium, magnesium and bicarbonates) have a massive impact on extraction and flavor. For best results look for a brewing water with the following parameters:
Calcium and magnesium: 60-120 mg/L
Bicarbonate: 40-80 mg/L
Generally, water with absence of minerals delivers thin, sharp, quickly fading cups.
On the other hand, water with too many minerals delivers bitter, chalky, flat flavors
Consider using a coffee-focused solution: mineral packets (e.g. Apax, Third Wave Water) or filter systems (like Peak Water or BWT).
Grind setting, your main control dial
Grind size is one of the most powerful levers in brewing. By adjusting grind size we change surface area affecting how fast/slow water will be able to extract compounds from coffee:
Finer grind = faster extraction rate (water extracts compounds quicker), more intensity, but risk of bitterness/astringency if overdone.
Coarser grind = slower extraction rate (water extracts compounds slower), lighter body and higher acidity, but risk of sourness and hollowness.
Beyond size, grinder quality matters:
Sharp, aligned burrs = uniform particles, clean balanced cups.
Dull/misaligned burrs = excessive fines and boulders, uneven extraction (sour and bitter in the same cup).
Think of grind as your “resolution setting”: the more precise your grinder, the more clearly you’ll taste what the coffee truly has to say.
Brew method
Your recipe (ratio, time, pours) and your device (material, geometry and filters) also shape the cup.
The best advice: choose a method you enjoy, but one that allows for consistency. A consistent method helps you isolate the impact of variables when experimenting. Inconsistent tools or techniques, on the other hand, only add noise and confusion.
That’s why I love tools like the Hario Switch, it’s simple, repeatable and makes experimenting easier.
A practical approach
When tasting at home, try this:
1. Record your recipe: ratio, water temperature, grind setting, pours and total brew time.
2. Note coffee details: roast date and degassing days.
3. Write first impressions: sweetness, acidity, body and bitterness.
4. Link sensations to at least two possible variables.
5. Change only one parameter at a time in the next brew.
This way, you build awareness and start connecting flavor outcomes with their real causes.
Conclusion
The beauty of coffee lies in its complexity. What feels like confusion at first can become curiosity and understanding if you learn how to read the cup.
Every coffee tells a story, your role as a brewer is to listen, not rush to judge.
And be curious to discover new coffees, our explorer subscription allows you to receive 2 different coffees every month!
Interested in learning more? Reserve a spot in our Professional Brewing Training and learn how to taste, brew and troubleshoot like a pro.
Matteo Pavoni