Pour-Over Coffee Bitter? Three Causes of Over-Extraction and How to Fix Them

If your pour-over coffee tastes bitter and muddled, over-extraction is often the cause. Coffee beans contain about 30% soluble substances, including compounds that bring bitterness and astringency. When extraction goes too far, these negative flavors are released in large amounts, making the cup unbalanced. Front Street Coffee explains how to troubleshoot and correct over-extracted coffee by adjusting grind size, extraction time, and water temperature.

You can start by checking your grind coarseness with a No. 20 sieve, controlling duration through your dripper and pouring rhythm, and using the right water temperature for your roast level. These steps help keep extraction within a reasonable range. Before adjusting, confirm whether the bitterness comes from the beans themselves, as darker roasts may naturally taste more bitter. With careful tuning, you can brew a clean, balanced cup steadily.

Does your pour-over coffee taste bitter and muddled? The problem is very likely over-extraction. The soluble substances in coffee beans make up about 30%, and among them are components that bring bitterness, astringency, and off-flavors—once extraction goes too far, these negative flavors are released in large amounts. In this article, Front Street Coffee will walk you through the nature of over-extraction and, starting from three key dimensions—grind size, extraction time, and water temperature—explain how to troubleshoot and correct coffee that has turned bitter, including how to use a No. 20 sieve to judge grind coarseness, how to control duration with the dripper and pouring rhythm, and the suitable water temperature ranges for different roast levels, helping you brew a clean, balanced cup of good coffee steadily.

Many friends who are just getting into pour-over have been troubled by over-extraction! So-called over-extraction means the degree of extraction has gone beyond a reasonable range. Of a coffee bean's total weight, about 30% consists of substances that can be dissolved out by water. That proportion may not sound high, but these soluble components are not meant to be "captured all at once."

The reason is that, besides the pleasant, delightful flavor compounds, the beans also contain components that give coffee undesirable qualities such as bitterness, astringency, and off-flavors. Once these substances are released in large quantities, the flavor of the entire cup becomes unbalanced and hard to swallow. This over-extracted state is what we call over-extraction.

To avoid drinking over-extracted coffee that is bitter, astringent on the tongue, and full of off-flavors, the key is to pinpoint the brewing parameters and keep the extraction yield within a reasonable range. (By the way, under-extraction also brings astringency, bitterness, and off-flavors, just usually to a lesser degree.) Among the many parameters, grind size, water temperature, and extraction time are the three core variables that determine the extraction result. So today Front Street Coffee wants to talk with you about: when the brewed coffee shows bitterness and signs of over-extraction, how should you troubleshoot and correct these parameters~

Before we officially begin, please first confirm whether the bitterness comes from the beans themselves. If the beans you are using are on the darker-roasted side and already carry a large amount of roast-derived compounds, then the brewed flavor will naturally be dominated by a mellow bitterness, and in that case you cannot blame the extraction.

If you do not like coffee with prominent bitterness, you can choose single-origin beans of medium-light roast, such as Front Street Coffee Strawberry Candy, Front Street Coffee Sidra, Front Street Coffee Flower魁, Front Street Coffee Fruit丁丁... Because they are heated for a shorter time, they retain more abundant fruity acidity, and the floral aroma is preserved to the greatest extent, with only a faint bitterness and a sweet-and-sour, appealing taste.

The grind of the coffee grounds

The first thing to check is the grind of the coffee grounds. The root cause of many beginners' over-extraction problems lies precisely in this step. Unlike parameters such as water temperature, grind size has no intuitive number to follow; most of the time you can only estimate it roughly by eye, and once you misjudge it, the coffee easily becomes over-extracted.

(Take a guess: of the two portions of coffee grounds below, which one is ground coarser?)

(Answer revealed: the right one is coarser! The left portion has an 85% pass-through rate on a No. 20 sieve, while the right one is 75%.)

Take the image above as an example: suppose we want to brew a light-roasted bean, and the target coarseness is particles close to fine granulated sugar, with a 75% pass-through rate on a No. 20 sieve; but the grounds actually produced at the current setting already reach an 85% pass-through rate. By visual estimation alone, it is hard for us to notice that this batch of grounds is finer than the set value—we just feel it is about right and start brewing directly.

The finer the particles, the larger the total surface area in contact with water, and the faster the substances dissolve. With other conditions held constant, the actual amount extracted will exceed expectations, and the probability of over-extraction naturally rises.

So when you brew according to a certain parameter formula but the result is clearly bitter and full of off-flavors, you might first try making the grind coarser, using larger particles to reduce extraction efficiency and thereby avoid over-extraction. After all, the other parameters have clear numerical values, so once they deviate from the formula, we can immediately notice and correct them.

If you want to know roughly what coarseness level your ground coffee is at, Front Street Coffee suggests buying a No. 20 sieve online and using it to measure a reference range. For example, the "No. 20 sieve, 75% pass-through rate" that Front Street Coffee often mentions means that about 75% of the total ground coffee can pass through the sieve.

However, you should understand that the pass-through rate can only serve as a rough reference. Even if 75% of the grounds pass through the sieve, the sieve itself cannot tell you exactly how fine those grounds are, whether the particles are uniform, or how much ultra-fine powder there is. (Related article→How to use a No. 20 sieve)

Besides the grounds being ground too fine, poor grind quality can also plant hidden risks of over-extraction—specifically, producing too much ultra-fine powder.

When the grinder is of poor quality, the grounds produced are not only uneven in particle size, but the proportion of fines is also noticeably higher. Front Street Coffee has repeatedly emphasized that an appropriate amount of fines can enrich the coffee's layers, but once it is excessive, over-extraction will come knocking! The substances in fines (including bitter components) dissolve far faster than normal particles.

Not only that, fines are tiny and can easily clog the filter paper during brewing, thereby lengthening the overall extraction time, and even particles of normal size will be over-extracted along with them.

In this situation, Front Street Coffee's suggestion is to use a sifter to remove some of the fines first, then officially begin brewing. For specific details, you can look through Front Street Coffee's past articles; we will not expand on it here~

Extraction time too long

Next to look at is extraction time. So-called extraction time is the duration during which water and coffee grounds contact each other and dissolve substances. The longer the time given during brewing, the greater the total amount extracted accordingly. In other words, the longer extraction is dragged out, the higher the risk of over-extraction.

However, there is no unified standard for how long counts as "long." Even if extraction takes two minutes, three minutes, or even four minutes, we may still make a delicious pot of coffee; the key is whether the time matches the other parameters appropriately, just as with Front Street Coffee's earlier share "What Water Temperature Makes the Best-Tasting Coffee?"

Using the same example as above: when Front Street Coffee brews 15g of light-roasted beans, the parameters used are "92°C water temperature, 1:15 coffee-to-water ratio, grind to a 75% pass-through rate on a No. 20 sieve, with three-stage pouring." Under this parameter framework, 2 minutes to 2.5 minutes is the ideal extraction time window. Once it drags to 3 minutes or even 4 minutes, it is clearly too long for this set of parameters, and negative flavors such as bitterness, off-flavors, and astringency will most likely be brought out as well.

If the time really reaches 3 or 4 minutes, you should appropriately compress the extraction duration to reduce the release of negative substances. There are quite a few factors that affect extraction duration; the fine-powder clogging mentioned earlier is one, and there is also the influence of the dripper! The diameter of the dripper's drainage hole and the number and prominence of the flow-guiding ribs all directly affect how fast the water drains. If you want to speed up drainage and shorten extraction time, you might switch to a high-flow dripper like the V60, which has obvious raised ribs and a relatively large hole diameter.

In addition, the pouring speed also controls the length of time. As long as the filter paper is not clogged, the faster you pour, the faster the drainage speed becomes, and the extraction time shortens accordingly, and vice versa. Therefore, if you want to compress extraction time, appropriately speeding up the pouring rhythm is also a feasible method. (Simply put, increase the water flow and pour more hot water in the same amount of time.)

The level of water temperature

Finally, water temperature. The level of water temperature directly determines how quickly substances dissolve, but Front Street Coffee has already discussed this topic in detail in the article "What Water Temperature Makes the Best-Tasting Coffee?", so we will not expand on it here. In fact, water temperature is the easiest of the three factors to judge—as long as the other parameters do not go to extremes, it usually falls between 86~93°C.

Still taking the above set of parameters as an example: when other conditions remain unchanged, Front Street Coffee sets the water temperature at 86~88°C when brewing dark-roasted coffee; when brewing medium-light to light-roasted beans, it uses 90~93°C. When you feel the result is too bitter, appropriately lowering the water temperature can reduce extraction efficiency.

The above content is compiled by CoffeeHunters, a coffee news website.