Chemex Grind Size Guide: How Coarse or Fine Should You Grind?

If you've just unboxed your first Chemex or you're struggling to get that perfect cup, the grind size is often the missing piece. With its thick paper filters and slow brewing process, the Chemex demands a specific grind size to extract the best flavors without over-extracting or under-extracting. In this guide, we'll walk you through the ideal Chemex grind size, how to adjust it, and common mistakes to avoid.

Whether you're using a classic model like the Eight Cup Classic CHEMEX® or a smaller version like the Three Cup Classic CHEMEX®, the grind size remains crucial. Let's dive into the details so you can brew with confidence.

Why Grind Size Matters for Chemex

The Chemex brewer uses a thick paper filter that traps most of the coffee oils and fine particles, producing a clean, crisp cup. However, this also means that the water has a slower flow rate, which increases the contact time between water and coffee. If your grind is too fine, the water will take too long to pass through, leading to over-extraction and a bitter taste. Conversely, if your grind is too coarse, the water will rush through too quickly, resulting in under-extraction and a weak, sour cup.

Finding the right grind size is about balancing extraction. The ideal Chemex grind is often described as 'medium-coarse' – similar to sea salt or raw sugar. This size allows for a brew time of about 4 to 5 minutes, which is the sweet spot for Chemex. With this grind, you'll extract the desirable flavors while avoiding bitterness and harshness.

• Too fine: over-extraction, bitter, astringent
• Too coarse: under-extraction, sour, weak
• Medium-coarse: balanced, sweet, clean

The Ideal Chemex Grind Size: A Visual Guide

To help you visualize, here's a simple comparison: the ideal Chemex grind should look like coarse sea salt. It should be uniform in size, with no powdery fines. If you're using a blade grinder, it's harder to achieve consistency, but a burr grinder will give you more control. If you're unsure, start with a medium-coarse setting and adjust based on taste.

Here's a quick grind size chart for reference:

• Extra fine (like powdered sugar): not recommended for Chemex
• Fine (like table salt): too fine, will clog
• Medium-fine (like sand): slightly too fine, may over-extract
• Medium (like ordinary sand): a bit too fine, but workable
• Medium-coarse (like sea salt): ideal for Chemex
• Coarse (like kosher salt): too coarse, under-extraction
• Extra coarse (like peppercorns): way too coarse

Adjusting Your Grind for Different Chemex Models

While the grind size is similar across all Chemex models, the brew time can vary slightly depending on the size. For larger models like the Six Cup Glass Handle CHEMEX®, you'll be brewing more coffee, which may require a slightly coarser grind to keep the extraction time within the 4-5 minute range. For smaller models like the Three Cup Classic, a slightly finer grind can help maintain the brew time.

If you're using a gooseneck kettle like the Stainless Steel Gooseneck Chettle®, you have better control over the pour rate, which can affect extraction. A slower, more controlled pour can compensate for a slightly finer grind, while a faster pour might require a coarser grind. Experiment with your technique to find what works best.

How to Dial In Your Grind: Step-by-Step

If you're not sure where to start, follow these steps to find your perfect grind size:

1. Start with a medium-coarse grind (like sea salt). 2. Brew a batch using your usual Chemex method. 3. Taste the coffee. If it's bitter and dry, your grind is too fine – go coarser. If it's sour and weak, your grind is too coarse – go finer. 4. Make small adjustments (one or two clicks on your grinder) and brew again. 5. Keep a log of your grind settings and brew times to replicate your favorite cup.

• Use a burr grinder for consistency
• Adjust one variable at a time (grind, dose, water temp)
• Keep a coffee journal to track your experiments

Common Mistakes to Avoid

One common mistake is using a grind that's too fine because you think it will extract more flavor. In reality, it leads to over-extraction and a bitter cup. Another mistake is not adjusting the grind when you change your coffee beans. Different beans have different densities and solubilities, so you may need to tweak your grind when you switch to a new roast or origin.

Also, be mindful of your water temperature. The ideal water temperature for Chemex is around 200°F (93°C). If your water is too hot, it can over-extract even with a correct grind. Use a thermometer or a kettle with temperature control to ensure consistency.

Mastering the Chemex grind size is the key to unlocking a delicious, clean cup of coffee. With a medium-coarse grind and a little experimentation, you'll be able to brew like a pro. Ready to put your skills to the test? Explore our range of Chemex brewers and accessories to find the perfect setup for your coffee ritual.