Why Grinding Finer Can Make Espresso Taste Worse

ESPRESSO DIAL-IN / COMMUNITY EXPERIMENTS

You open a new bag. The first espresso gushes out in 16 seconds. You grind finer. Better. Finer again. Now it tastes more sour. Another adjustment, another shot, and suddenly the extraction looks right but tastes wrong.

That is not a made-up horror story. It is almost exactly what happened in a five-shot experiment posted to r/espresso—and the more interesting part is what the user learned by going backward.

Community case study · These are independent Reddit users' experiences, reproduced here in summary with direct links to the original discussions—not product endorsements.

If you've ever used four or five double shots just to figure out a new bag, you're not alone. In another Reddit discussion, a home barista said dialing in new 250 g bags took four to six shots. At 18 g per dose, that's 72–108 g of coffee used for testing. Not necessarily thrown away, but still a lot of beans before breakfast starts feeling fun.

So what do real shot logs tell us? And what does coffee science actually support?

Experiment #1: Five shots, better numbers, worse espresso

In August 2021, a member of r/espresso documented five consecutive attempts at the same coffee. The first four used 18 g in and 36 g out. They kept grinding finer to approach the classic 25–30-second window.

Source: r/espresso, “Help dialing in! Getting sour when going finer”. These are one user's observations, not a controlled laboratory trial. Shot #5 also changed the dose, so it cannot isolate grind size alone.

The revealing moment is shot #2. It finished in 21 seconds and tasted better than several shots that looked more “correct” on the timer. By shot #4, going finer had increased visible channeling and made the coffee less pleasant.

This is why the timer is a diagnostic tool, not a scorecard. You can hit 26 seconds and still make a worse espresso than you did at 21.

That kind of sudden change is a reason to check the puck, not just the grinder dial. Here is a practical guide to spotting and reducing espresso channeling before pulling another test shot.

Experiment #2: A 30-second shot that tasted almost undrinkable

In January 2026, another r/espresso user described a frustrating day with a DF54 grinder and a new espresso machine. The starting recipe was about 17.5 g in and 70 g out in 30 seconds. It ran quickly with little pressure, but the user said it was the best-tasting shot of the session.

They then ground finer and changed the dose, trying to reach higher pressure and a more conventional recipe. Eventually, they reached 18 g in, 40 g out, 30 seconds, and roughly 8 bar at peak pressure. Yet they described the result as increasingly astringent and unpleasant.

Source: r/espresso, “Coffee tastes astringent when dialed in”.

This does not prove that fast shots are better, or that 30-second shots cause astringency. The dose, beverage yield and grind all changed, and the first shot was a much longer ratio. What it does show is a common trap: chasing a target pressure, time or ratio while ignoring what is happening in the cup.

In a separate Reddit experiment, a home barista described a 42-second shot as more drying, a 35-second shot as less drying, and a 30-second shot as sour without that dry sensation. The results were imperfect, but they captured something many dialing-in charts miss: sourness, bitterness and astringency are different sensations, and none can be diagnosed from shot time alone.

If the sour-versus-dry flavor swing sounds familiar, our espresso sour-or-bitter troubleshooting guide separates possible extraction problems from the coffee’s natural acidity.

Why does changing coffee beans mess up your grind setting?

Because beans are not interchangeable little brown pellets.

A 2022 study in European Food Research and Technology examined how changing coffee batches and blends affects espresso flow. In one comparison, two coffees ground at the same setting produced markedly different flow rates; one was roughly double the other. That is a good reason not to treat yesterday's grinder number as a universal recipe.

Then there is the relationship between grind size and water flow. A 2020 paper in Matter combined a mathematical model with espresso experiments and found that extraction yield did not simply improve as grinding became finer. At very fine settings, uneven flow can undermine extraction consistency.

And in a 2024 Scientific Reports study, researchers found that increasing the proportion of very small coffee particles reduced puck permeability and slowed espresso flow. Importantly, the study did not find a blanket sensory penalty for adding fines. That matters: fines affect the way water moves, but “fines = bad taste” is not a scientific shortcut.

In other words, the grind dial changes more than the number of seconds on your stopwatch. And a correct-looking shot does not guarantee even extraction—or a flavor profile you enjoy.

New to the mechanics behind those changes? Start with how grind size affects espresso flow, then come back to these shot-by-shot experiments.

Experiment #3: Can bigger adjustments save beans?

A December 2025 Reddit post proposed an “overshoot” approach. Rather than moving the grinder by tiny amounts over and over, the user made a larger adjustment after a fast, sour shot. The next shot was too restrictive; they backed off partway and reported a good result on the third attempt.

Source: r/espresso, “The overshoot method”.

The underlying idea is useful: if you know one setting is clearly too coarse and another is clearly too fine, you can work inside that range instead of searching blindly. But the original post describes one person's method, not proof that three shots will always be enough. You also do not need to intentionally choke your espresso machine just to learn where the boundary is.

Here's a less wasteful way to borrow the idea.

A practical two-pass method for a new bag

Pass 1: Get the flow into a workable range.

1. Start from a known reference. Use your last successful setting for a coffee with a similar roast profile. It is a starting point, not a promise.
2. Keep the dose steady. Choose a dose that suits your basket—18 g is a common example—and keep the tamping, distribution and machine routine as consistent as you can.
3. Set a target yield. A 1:2 recipe, such as 18 g in and 36 g out, is a reasonable first test, not an obligatory final answer.
4. Pull one shot and taste it. Record the time using the same timing convention each time. If it gushes dramatically, go noticeably finer. If it nearly stalls, go coarser. If it is close, make smaller changes.
5. Stop chasing the timer once the shot is workable. If a 23-second shot tastes good, there is no prize for making it last 30.

Pass 2: Dial in flavor, not just flow.

None of these is an infallible diagnosis. Roast level, water, temperature, bean character and personal preference all matter. If you cannot tell whether a shot is sour, bitter or drying, try a salami shot: collect the beginning, middle and end of one extraction in separate cups, then taste each and the recombined drink. Reddit users have documented how revealing—and sometimes confusing—this exercise can be. It is a palate-training tool, not a guarantee that one particular segment is always the problem.

How to waste less coffee without pretending every shot must be perfect

A popular r/espresso conversation about dial-in waste produced a surprisingly sensible theme: a shot that misses your preferred recipe isn't necessarily trash. Some people make a milk drink, some turn a fast shot into a longer drink, and some just adjust the grinder for tomorrow.

There are a few practical habits worth stealing:

• Record the useful setting. Save the bean name, roast date, dose, yield, grinder position, time and one tasting note. “21 s, sweeter than 26 s” is more helpful than “pretty good.”
• Change one thing at a time during diagnosis. Changing the dose, grind, yield and temperature together makes the next result difficult to interpret.
• Don't purge by habit. If your grinder retains a meaningful amount of old grounds, a small purge may help. A genuinely low-retention single-dose workflow can reduce that carryover, but the required amount depends on the machine and the way it is used.
• Don't halve the dose just to save beans. Using 9 g in a basket designed around 18 g changes puck depth and flow; it doesn't simply give you a cheaper preview of the same recipe.
• Take a break. Five double shots are already a lot of coffee to taste in one sitting. You can learn from a shot without drinking every last drop or forcing yourself through excessive caffeine.

A simple log takes about ten seconds:

Bean / roast date → dose → yield → seconds → grinder setting → taste → next change

That one line means the next bag starts with useful evidence instead of guesswork.

Switching beans is not only about the setting. Old grounds carried over from previous doses can also blur a test. Our coffee grinder retention and exchange guide explains when a purge may actually help.

What does the grinder actually change?

A grinder cannot make every coffee taste good automatically. But it can make the process less frustrating.

For espresso, useful features include sufficiently fine grind adjustment, a repeatable reference scale, and low retention when you change beans or settings. Stepless adjustment is particularly helpful when one setting is a little too fast and the next is a little too slow. If you're curious about that trade-off, see our stepless vs. stepped coffee grinder guide.

The real finish line

The most useful lesson from the five-shot Reddit experiment isn't that you should grind coarser, or finer, or aim for 21 seconds.

It's that the user's best-tasting attempt did not line up neatly with the supposedly ideal time. When the coffee became more sour and channeling increased, going back was progress—not failure.

Treat the first shot as information. Treat the next one as a test. And when it tastes good, stop trying to fix it just because the clock says you should.

Quick FAQ

Does every new bag of espresso beans need a new grinder setting?
Not always. Sometimes the previous setting works well enough, but different beans and even different batches can change flow at the same grind setting.

Is 18 g in, 36 g out, in 30 seconds the ideal recipe?
It's a familiar starting point. Taste, extraction evenness and the coffee itself decide the final recipe.

Why does espresso taste more sour after I grind finer?
One possibility is increasingly uneven flow or channeling, but sourness can also reflect ratio, temperature, the coffee's natural acidity or how you perceive the flavor. Look at the whole process, not just grind size.

How many shots should dialing in take?
There is no fixed answer. Reddit users report everything from a drinkable first shot to four or six rounds with unfamiliar beans. The goal is not a magic number—it's learning from each attempt without repeatedly changing everything.

Sources and further reading

Reddit case studies

• Five-shot grind-size experiment, r/espresso (2021)
• Astringency while approaching textbook settings, r/espresso (2026)
• Sour-versus-astringent experiments, r/espresso (2021)
• The overshoot method, r/espresso (2025)
• How much coffee gets wasted when dialing in?, r/espresso (2023)

Research and technical guidance

• Test of an innovative method to prepare coffee powder puck, improving espresso extraction reliability (2022)
• Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment (2020)
• The Role of Fines in Espresso Extraction Dynamics (2024)
• Espresso Aficionados: Dialling In Basics

Editor's note: Reddit posts are first-person accounts, not controlled product tests. The article keeps their reported recipes and outcomes separate from the scientific studies.