Mastering the grind: How humidity affects your CBTL espresso

There’s nothing quite like the satisfaction of pulling a perfect espresso shot at home using your favorite Coffee Bean & Tea Leaf beans. You’ve got the machine, the high-quality grinder, and the perfect beans. Yet, some days your espresso is rich and syrupy, and other days it’s disappointingly sour or bitter, even when you haven’t changed a thing. What gives? The answer might be in the air around you. Ambient humidity is a powerful, often-overlooked variable that dramatically impacts how coffee grinds and extracts. This article will demystify the relationship between humidity and your coffee, providing you with the knowledge and practical steps to manage these changes and achieve consistently delicious CBTL espresso every single day.

Why humidity is the silent variable in espresso

Roasted coffee beans are hygroscopic, which means they readily absorb moisture from their environment. This simple scientific fact is the root of many espresso inconsistencies. When the air is humid, your CBTL beans soak up that moisture, becoming slightly softer and heavier. Conversely, on a dry day, they release moisture, becoming harder and more brittle. This change in the physical state of the bean has a direct and significant impact on the grinding process.

When you grind softer, moisture-laden beans, the particles tend to be finer and clump together more easily. Even at the same grinder setting, the resulting grounds will offer more resistance to water during extraction. On the other hand, dry, brittle beans shatter into more varied and generally larger particles (boulders and fines), creating less resistance. This is the core of the problem: your grinder setting is a constant, but the coffee bean itself is not. This leads directly to extraction issues. The clumpy, fine grounds from a humid day can cause a slow, over-extracted shot that tastes bitter and harsh. The coarser grounds from a dry day can lead to a gusher—a fast, under-extracted shot that tastes sour and weak.

Recognizing the signs of humidity-related issues

The first step to managing a problem is learning to identify it. Your espresso machine and your senses will give you all the clues you need to know if humidity is wreaking havoc on your brew. Pay close attention to your daily coffee ritual, and you’ll start to notice patterns.

• Visual cues in the grinder: On high-humidity days, you’ll likely see more clumping in the grounds as they come out of the grinder chute. The coffee may look fluffier and stick to the sides of your portafilter basket. On low-humidity days, you might notice more static, causing grounds to fly everywhere.
• Observing the shot: Your most important tool is a timer and a scale. A shot that typically takes 28 seconds might suddenly choke the machine and run for 40 seconds on a rainy day. On a dry, crisp morning, that same shot might gush out in just 15 seconds. You may also see channeling—where water punches a hole through the coffee puck—which is more common with the uneven grounds produced on dry days.
• Tasting the result: Ultimately, your palate tells the final story. If you haven’t changed your recipe but your CBTL espresso suddenly tastes astringent and bitter, you’re likely over-extracting due to high humidity. If it’s thin, sour, and lacks sweetness, you’re probably under-extracting because of low humidity.

Practical strategies for adjusting your grind

Once you’ve identified the problem, the solution is straightforward: you need to adjust your grinder to counteract the effects of the humidity. This process, known as “dialing in,” isn’t a one-time setup but a continuous series of micro-adjustments.

The core principle is simple: do the opposite of what the humidity is doing to your coffee.

On a high-humidity day, the moisture is making your coffee grind finer and clumpier. To compensate, you need to make your grind setting coarser. This will enlarge the particle size, reducing the resistance in the coffee puck and allowing the shot to flow at the correct pace, preventing over-extraction. You might only need to move your grinder’s adjustment collar by one or two small notches to see a significant difference.

On a low-humidity day, the dry beans are shattering into coarser particles. To compensate for this, you must make your grind setting finer. This will decrease the particle size, creating more resistance and slowing down your shot to achieve a proper, balanced extraction and avoid a sour result.

Think of it as a daily conversation with your coffee. Before your first shot of the day, consider the weather. Is it raining? Is the air dry? Be prepared to make a small adjustment from where you left off the day before. This proactive approach will save you from sinking a bad shot and wasting precious CBTL beans.

A summary of adjustments for humidity

To keep things clear, it’s helpful to have a simple reference guide. Understanding these cause-and-effect relationships will empower you to react quickly and effectively to changing atmospheric conditions. Good puck preparation, such as using a distribution tool to break up clumps, becomes even more critical on humid days. Similarly, a light spritz of water on your beans before grinding (a technique called RDT) can drastically reduce static on dry days.

Conclusion

Mastering espresso is a journey of controlling variables, and humidity is one of the most dynamic. While it may seem frustrating at first, learning to adapt to it is a hallmark of a skilled home barista. By understanding that moisture makes your CBTL beans softer and dry air makes them more brittle, you hold the key to consistency. Remember to observe your grind, time your shots, and taste the results. On humid days, grind coarser to fight the clump; on dry days, grind finer to add resistance. Embracing this daily ritual of dialing in transforms a potential problem into a rewarding part of your craft, ensuring that every cup of espresso you brew is a true reflection of the quality beans you started with.