What to Do with Too Much Coffee Fines? How to Brew with Fine Coffee Grounds? What's the Difference Between Fine and Coarse Grounds?

To better extract flavor compounds from coffee, we grind coffee beans to increase the surface area for water contact, thereby enhancing extraction efficiency. However, whether it's a grinder costing several hundred dollars or one costing tens of thousands, without exception, the ground coffee they produce will contain a certain amount of fine particles!

What Are Coffee Fines?

So-called coffee fines refer to coffee particles smaller than 0.1mm in diameter, which feel somewhat similar to flour when rubbed between fingers. The target particle size we typically aim for when grinding is in the range of 0.6-0.8mm, making it evident that the difference between these two is substantial.

Why Do Fines Occur?

Fines are primarily produced because the grinding mechanism of coffee grinders first applies pressure to whole coffee beans, causing them to crack into fragments, which are then cut and ground into small particles. During this compression process, fines are generated due to the brittleness of coffee beans (similar to how crumbs are produced when breaking cookies). This means that the more brittle the coffee beans, the more fines will be produced. Additionally, the quantity of fines is influenced by the quality of the grinder. When the grinder quality is better and the burrs are sharper, the quantity of fines is reduced, and vice versa.

FrontStreet Coffee often says, "The presence of fines is a double-edged sword" because their existence has both advantages and disadvantages. The benefit is that because fine particles are extremely small, their flavor compounds dissolve more completely during extraction. Due to their higher extraction efficiency, when properly extracted, this can give coffee a richer layered complexity. Of course, the prerequisite is proper extraction and appropriate quantity.

The Double-Edged Sword of Fines

The excessively high extraction efficiency is both an advantage and a disadvantage of fines. Because they extract more efficiently, they are more likely to over-extract compared to other normally-sized particles. When extraction is improper, even if fines are present in small amounts, the coffee will exhibit obvious bitterness, harshness, and astringency. Because we are extremely sensitive to bitterness, even small amounts of bitterness can be easily detected by us.

Furthermore, because fine particles are extremely small, they can cause blockages during the extraction process. When the filter paper's pores become clogged, the flow channels for coffee liquid are reduced, prolonging extraction time. Excessive extraction time causes those regular-sized particles to receive more extraction, making the coffee more likely to experience over-extraction.

Managing Fines in Your Brew

Therefore, you can decide whether to keep or remove fines based on the amount produced after grinding. Generally, as long as there's no clogging in the filter cup or muddy appearance of the coffee bed during brewing, this means the quantity of fines isn't excessive enough to affect the brewing process, and you can confidently enjoy the positive contribution that fines bring. However, if clogging occurs frequently during brewing, the coffee bed appears as muddy as a swamp, and the coffee shows over-extraction characteristics such as bitterness, harshness, and astringency, then there's no doubt that it's likely caused by excessive fines from grinding.

In such situations, besides upgrading to a better quality grinder, we can also use a flour sifter (coffee sieve) to solve the problem of excessive fines.

FrontStreet Coffee's Approach to Fines

If using a sieve to remove fines, FrontStreet Coffee does not recommend removing all of the filtered fines. This is because without the presence of fines, coffee won't display such outstanding layered complexity. Therefore, FrontStreet Coffee suggests that after sifting out the fines, you shouldn't rush to discard them. Instead, you can use the following two methods to let fines regain their true value.

Method 1: Adding Back Some Fines

After sifting out the fines, you can add some of them back into the coffee grounds. As long as the quantity isn't excessive, it won't affect the brewing process or the taste of the coffee.

For pour-over coffee, a fine content of approximately 10-15% in the coffee grounds is most suitable. Exceeding this ratio can easily lead to negative situations such as clogging and over-extraction.

Method 2: Adding Fines Mid-Brew

The second method is something many friends often do. Before brewing, first sift out the fines from the coffee grounds, then when the brewing process reaches the halfway or two-thirds point, add the sifted fines back in for extraction.

This approach has two benefits: first, it maximizes the value of fines, and second, it reduces waste. This is because some lower-quality grinders produce an excessive amount of fines—15g of coffee beans might yield 3-4g of fines. If we choose to discard all these fines, we would need to grind additional beans to make up for the loss, which is particularly unfavorable when using expensive beans. Therefore, in such situations, we might try adding half of the fines back into the coffee grounds, then add the remaining half when the brewing process reaches the two-thirds mark. This way, we won't be affected by excessive fines while still enjoying their positive contribution!

Application in Multi-Stage Brewing

All multi-stage brewing methods can use this approach, adding the fines when the brewing process reaches approximately the two-thirds point. Taking three-stage pouring as an example, FrontStreet Coffee adds the fines after completing the second stage pour, keeping the brewing parameters consistent with before. However, it's important to note that during the third stage pour (after adding the fines), we should try to avoid using too much water flow to stir the coffee bed, as this could easily cause fines to be washed to the bottom and clog the filter paper. This might be acceptable for those extraction-resistant, light-roasted coffee beans, but for dark-roasted beans that are prone to over-extraction, it's best to avoid clogging situations~

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473