What Causes Slow Pour-Over Coffee Flow? How to Brew High-Density Light Roast Coffee?

The Challenge of Brewing High-Density Coffee Beans

"Clogged," "under-extracted," "bitter," "thin" - these are common issues encountered when brewing high-density coffee beans. Many beginners find this frustrating because regardless of adjustments, it's always difficult to brew a delicious cup with these beans. Either it's over-extracted due to excessive extraction time, or it shows uneven and insufficient extraction due to excessive bypass water.

Although FrontStreet Coffee has shared many related articles, many friends still don't know how to handle these coffee beans that easily clog or cause brewing failures. That's okay - today FrontStreet Coffee will share again how high-density coffee beans should be brewed~

Before diving into brewing techniques, let's first understand why high-density beans are so challenging to brew.

Why Are High-Density Beans So Difficult to Brew?

So-called high density refers to coffee beans that are hard and have a compact structure. Typically, these beans are grown at higher altitudes or are lightly roasted. Compared to lower-density beans, high-density coffee tends to settle more easily at the bottom of the filter during brewing. This reduces the flow channels for hot water, making it very easy for water to accumulate in the filter during brewing, as the water injection rate is much higher than the drainage rate.

To put it simply, the amount of water poured in exceeds the amount draining out, causing water to accumulate in the filter. This can lead to the two situations FrontStreet Coffee mentioned at the beginning: over-extraction and uneven extraction. If we don't build a high enough coffee bed during brewing, excessive water injection will submerge the coffee grounds. This provides hot water with "alternative paths" that avoid contact with the coffee grounds, seeping through other parts of the filter and causing uneven extraction. When water accumulates in the filter for too long, the coffee will release excessive substances due to prolonged contact with the grounds, resulting in obvious bitter, complex, and astringent flavors - what we commonly call over-extraction.

Many friends might think of adjusting to a coarser grind to increase drainage speed after seeing these examples. Indeed, coarser coffee grounds can increase flow rate and reduce some clogging. However, only somewhat. Minor adjustments to grind size won't significantly impact flow rate, while making it much coarser, although it can significantly increase flow rate, creates another extraction problem - susceptibility to under-extraction. Because the coffee grounds are too coarse, hot water needs more time to penetrate the interior, making it difficult to fully dissolve all substances within the limited time. And high-density coffee beans are harder to extract than regular beans, so overly coarse grinding will further exacerbate under-extraction.

Therefore, FrontStreet Coffee does not recommend adjusting to a coarser grind as the primary correction method. Of course, this assumes your grind size is already correct. The coffee bed after brewing should have particles that are neither overly distinct (too coarse) nor muddy (too fine grind/excessive fines). For clogging, FrontStreet Coffee suggests adjusting from another direction - reducing the water injection rate.

How to Brew High-Density Coffee Well?

Reducing the water injection rate can narrow the gap with the drainage rate, preventing water levels from submerging the coffee grounds and ensuring every drop of hot water contacts the coffee. This allows full dissolution of flavor compounds in the coffee. Meanwhile, we can also lower the water pouring height. This reduces the water column's intensity, thereby minimizing the agitation of coffee grounds and preventing fines from quickly settling at the bottom and clogging the filter paper.

Often, clogging isn't solely caused by excessive density of coffee grounds settling and accumulating, but also by fines blocking the filter paper. When we lower the water pouring height combined with reducing the injection rate, the coffee grounds experience minimal agitation during brewing, significantly reducing the occurrence of over-extraction due to prolonged extraction time. Without further ado, let's have FrontStreet Coffee demonstrate how to brew high-density coffee well! (If clogging is caused by excessive fines, you'll need to refer to the article "What to Do With Too Many Fines?")

This time, FrontStreet Coffee is using a popular recent selection - Ethiopia·Gesha Village Red Label. It's grown at an altitude of around 2000 meters and is a lightly roasted coffee bean, perfectly embodying the two main factors that make brewing challenging. There are two extraction approaches: one is the multi-stage brewing method that FrontStreet Coffee has shared before, which divides the total water injection into 4-5 segments, suitable for beginners who haven't mastered water control proficiency. For details, you can refer to the article "Brewing Method for High Sweetness, Non-Clogging Light Roast Coffee," which FrontStreet Coffee won't repeat here. The other approach, which FrontStreet Coffee is sharing in this article, is more suitable for those with some proficiency in water control. Because it requires longer injection duration and maintaining small water flow throughout the process. The extraction parameters remain the same as usual, as follows:

Coffee amount used: 15g
Grind level: Ek43 setting 10, 75% passing through #20 sieve, fine sugar grind
Coffee-to-water ratio: 1:15
Brewing temperature: 92°C
Brewing method: Three-stage
Filter cup used: V60

First, we'll use twice the coffee amount in water for a 30-second bloom.

After the bloom ends, we inject the second portion of hot water, totaling 120ml. This portion is injected entirely with small water flow (average 3ml/s), starting from the center and slowly spreading outward, then continuously repeating the "mosquito coil" circular pouring until this portion of water is completely injected.

At 1 minute and 10 seconds, FrontStreet Coffee completed the second water injection. Then, after waiting for the hot water to mostly drip through, we can begin injecting the next portion of hot water (at this point, FrontStreet Coffee's brewing time reached 1 minute and 45 seconds). Similarly, the third portion of hot water is still injected in small circular flows, totaling 75ml. However, this time the circles are smaller, as we need to focus on extracting the central coffee grounds. When all the hot water is injected (at this point, FrontStreet Coffee's brewing time is at 2 minutes and 10 seconds), we only need to wait for the dripping to complete before removing the filter cup and ending extraction.

Total time: 2 minutes and 31 seconds! Although longer than usual extraction time, the coffee didn't develop any negative flavors from over-extraction, thanks to the lower agitation intensity and the fact that the coffee beans are harder to extract.

Through tasting, FrontStreet Coffee detected citrus and berry acidity and sweetness, strawberry fermentation aroma, and rose floral notes in the cup. The overall flavor is balanced and gentle, with rich layers and a long-lasting oolong tea aroma in the aftertaste. If you're also troubled by some high-density or easily clogging coffee beans, why not try these two brewing methods~

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