Why Does My Coffee Taste Sour or Bitter? A Grind-Size Guide
There is a particular disappointment in brewing a coffee you were looking forward to, taking a sip, and wondering where all those lovely tasting notes went. Instead of sweet fruit or chocolate, you get an unpleasant sharpness. Or maybe the cup is so bitter it seems to dry out your mouth.
Before you write off the coffee, start with one of the simplest tools you have: the grinder. A small adjustment can make an impressive difference. The trick is knowing what to change—and resisting the temptation to change everything at once.
First, what does coffee extraction mean?
When hot water meets ground coffee, it dissolves some of the compounds responsible for flavour, aroma and texture. That process is called extraction. Your brewing method, grind size, water, temperature, dose and contact time all influence the result.
It is worth distinguishing strength from extraction. A beverage can taste strong because it contains a high concentration of dissolved coffee, yet still be unevenly extracted. Adding more grounds does not necessarily solve a flavour problem.
Why does my coffee taste sour?
An unusually thin, aggressively sharp cup can indicate that not enough of the coffee's soluble material reached the water—or that the extraction was uneven. But acidity itself is not a fault. A lively Ethiopian coffee might naturally have apple, citrus or berry-like acidity.
Ask whether the sharpness is balanced by sweetness and a pleasant finish. If the cup feels hollow rather than vibrant, try moving your grinder one small step finer while holding the rest of the recipe steady. Brew again and compare. Did sweetness improve? Did the finish feel more complete? That's the information you need.
Why does my coffee taste bitter?
A harsh, drying or muddled cup may point toward aggressive or uneven extraction. Try a slightly coarser grind and compare it with the previous cup. Also consider whether you're tasting a dark-roast characteristic, or whether your water, temperature and equipment need attention.
There is an important catch: grinding finer usually gives water more surface area to work with, but going too fine can reduce the flow of water through an espresso puck and produce uneven extraction. That means a very fine grind can sometimes make a cup both unpleasantly sharp and bitter. Finer is not always better.
How to dial in filter and pour-over coffee
Start with a brewing recipe you can repeat. For filter coffee, a useful initial range is approximately 1 part coffee to 16–17 parts water by weight. Your ideal ratio may be different, and that's fine.
- Use the same coffee dose, water amount, brewer and filter for your comparison.
- Grind at your usual setting and brew as you normally would.
- Taste the coffee while warm, then again as it cools. Flavours can become easier to distinguish at lower temperatures.
- If it tastes thin and unpleasantly sharp, try a slightly finer grind. If it tastes heavy, harsh or drying, try a slightly coarser one.
- Change only one setting at a time, taking a quick note of the result.
Don't chase somebody else's grinder number: two different grinders can produce very different results at the same marked setting.
How to dial in espresso
Espresso makes small adjustments especially noticeable. Start by weighing the dry coffee dose and the beverage that lands in your cup. An example baseline is 18 g of ground coffee yielding 36 g of espresso, or a 1:2 ratio.
Keep that dose and yield relatively consistent while you test small grind adjustments. Track the time, but treat it as a clue rather than a pass-or-fail score. Different coffees, baskets and machines can produce excellent espresso at different shot times.
If your shot runs unpredictably, examine distribution and puck preparation as well as grind size. Water may be passing through some parts of the coffee bed more readily than others.
From our roasting partner: how Lee approaches dialling in
Lee at Quietly Coffee, the roasting partner for Phoenix Coffee, offers a useful way to troubleshoot extraction: when a brew seems weak and hollow, a finer grind may help water extract more of the coffee's soluble flavours; when a brew seems harsh or overly intense, try a slightly coarser setting. Lee also points out the important limit: extremely fine particles can clump and encourage channeling, so changes should be small and judged by flavour rather than a setting alone.
Quietly's Fall 2026 offer sheet suggests a starting filter-brewing ratio of approximately 1:16.5 (coffee to water, by weight). For espresso, Lee provided coffee-specific starting points: Allie & Lennie, 28–33 seconds at about 1:2.2; Magnolia, 31–36 seconds at about 1:2.3; and Shady Lane, 29–34 seconds at about 1:2.1. He also listed 201°F (approximately 94°C) and 9 bar as example espresso settings.
These are roaster-suggested starting recipes from a particular offer sheet, not fixed specifications for every harvest, grinder or machine. Phoenix coffees change over time, so use the current producer details and your own palate to make the final adjustment.
Source: Lee, Quietly Coffee, Fall 2026 offer sheet, p. 6. Adapted and credited with permission. Phoenix Coffee's interpretation and additional brewing guidance are our own.
Three mistakes that make troubleshooting harder
- Adjusting several variables at once. If you change dose, grind and water temperature together, you won't know which change helped.
- Calling every bright coffee under-extracted. Pleasant acidity can be one of the best things about a coffee.
- Treating a recipe as a rule. A starting ratio is useful because it is repeatable, not because it is the only correct way to brew.
Let the coffee tell you what it needs
Start with the flavour notes and processing information on the product page, then listen to your own palate. Our filter and pour-over coffees offer different expressions of clarity, sweetness and fruit. If you're pulling shots, explore our espresso selections and use the same measured approach.
Phoenix Coffee is an independent specialty coffee retailer, and our coffees are roasted by Quietly Coffee. The producers and processing details change with each offering, which is one reason brewing remains interesting. Good coffee is not a fixed number on a grinder; it's a conversation between the bean, the brewer and your taste.
Further reading
For the research behind the limitations of very fine espresso grinds, see “The role of fines in espresso extraction dynamics” (Scientific Reports, 2024), and the Specialty Coffee Association's discussion of dialing in.
Video guides for curious brewers
For more hands-on demonstrations, explore James Hoffmann's “How I Dial-In Espresso – Part #1” and Lance Hedrick's espresso extraction tutorial. They are independent educators with different ways of approaching espresso, and both provide useful context for experimenting with dose, grind, yield and taste. These links are educational references; neither creator is affiliated with or endorses Phoenix Coffee.
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