Be Careful! This Habit Can Make Your Coffee Taste Worse

 When you pour coffee grounds into your dripper and see a surface that looks uneven—like in the photo below—what do you usually do?

A: Tap it flat
B: Tap it flat again
C: Either A or B

If you’re like most people, you’d probably go for tapping the dripper to even out the surface of the coffee bed. It’s not just about making it look neat—many believe that a smooth, level coffee bed ensures more even extraction. And that’s actually true! Compared with an uneven coffee bed, a flat one does allow hot water to flow more evenly through the grounds, which helps you brew a better-tasting cup.

But—here’s the catch—how you flatten the bed matters. If you’re not careful, tapping too much can actually make your coffee taste worse. One major reason for this is something called the Brazil Nut Effect.

What Is the Brazil Nut Effect?

The Brazil Nut Effect describes a phenomenon that occurs when you shake or tap a container filled with particles of different sizes. The larger particles gradually move to the top, while the smaller ones settle toward the bottom.

This effect doesn’t just apply to nuts—it’s also very common in coffee! Coffee grounds from your grinder aren’t all the same size; some are large, others are fine. So when you tap the dripper, the finer particles tend to sink, while the larger ones rise to the top.

And that can create two main extraction problems:

1. Uneven Extraction

When the fine particles accumulate at the bottom, it becomes harder for the hot water during blooming to evenly wet all the grounds.

Fine particles pack tightly together, leaving very little space between them. After frequent tapping, these tiny gaps get even smaller, making it difficult for water to flow through. And because water is “lazy”—it prefers the path of least resistance—it’ll move through the looser areas near the edges of the dripper instead of soaking evenly through the dense bottom layer.

If you’re pouring a large amount of water (like during the main pour of a pour-over), this doesn’t matter much. But during the blooming phase, you’re only using a small amount of water—usually about twice the coffee weight. When the coffee bed is too compact, that small amount of hot water won’t be able to fully saturate all the grounds.

I’ve tested this many times. With cone-shaped drippers and dense grinds, repeated tapping often caused parts of the coffee bed—especially near the bottom—to remain dry even after blooming.

Dry grounds can’t release their gases properly or extract their full flavor potential. As a result, your coffee ends up tasting flat, with muted flavors and less body.

2. Over-Extraction

Excessive tapping can also cause over-extraction. Here’s why: as the fine particles settle downward, they include ultra-fine coffee dust that can clog the filter paper’s pores. The more and harder you tap, the higher the chance of clogging.

Once those pores get blocked, the flow of water slows down, extending the brewing time. Longer contact between water and coffee grounds means higher extraction—and before you know it, you’ve got a bitter, over-extracted cup.

So, Should You Stop Tapping Altogether?

Not at all! You can still tap—it’s just about how much you do it. A gentle tap or two is totally fine. Just avoid overdoing it with strong or frequent knocks. That way, you won’t cause the coffee particles to migrate too much, and you’ll keep your extraction balanced.

Of course, there are other ways to level your coffee bed—just remember the same principle: don’t over-handle it. Sometimes, less really is more.