Front Street Coffee has found that many friends always run into this problem when they first start learning coffee brewing: they find that the coffee they brew doesn't taste good, but they can't quite say exactly what's wrong with it. To be honest, if we want to brew a good cup of coffee, besides learning the underlying logic of brewing and mastering the correct extraction parameters, [more…]

When brewing coffee, under-extraction or over-extraction will both bring unpleasant flavors. Starting from the golden cup extraction standard, this article explains the origin of the 18%–22% extraction yield, and details how to judge whether coffee is under-extracted or over-extracted by tasting sour, sweet, bitter, and other flavor expressions. At the same time, for common extraction problems in home brewing, it provides practical suggestions for adjusting grind size, water temperature, and brewing rhythm, helping coffee lovers easily brew a balanced and tasty cup. [more…]

When brewing coffee, unpleasant flavors often come down to two situations: under-extraction or over-extraction. Front Street Coffee has found that many beginners can taste that something is off with their coffee but can't pinpoint the problem. This article starts with the definition of the Golden Cup standard, explaining the reference range of an 18%–22% extraction yield, while also pointing out that the Golden Cup is not an absolute standard and that coffee bean quality can affect the results. It then details the three main signs of under-extraction—watery flavor, thin body, and sharp sourness, astringency, and saltiness—as well as the characteristics of over-extraction, such as pronounced bitterness, dryness, and woody off-flavors. Finally, it offers a practical adjustment plan that uses grind size as the variable while keeping water temperature, time, and water amount fixed, helping everyone quickly find the parameters that suit them. [more…]

When making espresso, extraction occasionally ends prematurely due to an accidental touch or oversight. Some people wonder: since it wasn't extracted enough, can we just press the button again to continue extracting, like with pour-over? Front Street used the Warm Sun blend to conduct a comparative experiment, testing three scenarios: normal extraction, extraction resumed after being interrupted midway, and extraction resumed after being interrupted near the end. The results showed that after restarting, the flow rate was extremely fast, the color was pale, and the flavor was noticeably thin; even with further extraction, it was difficult to fully extract the remaining substances. This article will start from the principle of pressurized extraction in espresso machines to explain why the same puck is not suitable for secondary extraction, and what the more reliable approach is when an accidental interruption occurs. [more…]

If you mistakenly press the stop button during espresso extraction before reaching the target yield, can you simply press it again to continue extraction? This article compares three espressos—normal extraction, mid-extraction stop-start, and stop-start near the final phase—to analyze how segmented extraction affects the color, flavor, and concentration of the coffee liquid. Front Street Coffee uses the Warm Sun blend, testing with 20g of grounds extracted to 40ml at a 1:2 brew ratio, to reveal why under pressurized extraction, changes in the puck structure cause an overly fast flow rate and under-extraction during a second extraction, along with operational recommendations. [more…]

For more specialty coffee knowledge, please follow our WeChat public account: Front Street Coffee (FrontStreet Coffee). Those who have read Front Street's popular science articles may have noticed that Front Street rarely specifies exact extraction times the way it does when explaining pour-over coffee, because espresso extraction is about more than just [more…]

Judging whether a cup of coffee tastes good varies from person to person, but when it comes to the defective flavors caused by extraction problems, people often reach a consensus. This article, from the perspective of Front Street, introduces the specific taste manifestations of under-extraction and over-extraction. When under-extracted, coffee presents sharp acidity, noticeable saltiness, a lacking finish, and thin flavor; over-extraction, on the other hand, allows bitterness to greatly suppress other flavors. The article also specifically reminds us not to rigidly adhere to the golden cup extraction numbers, because bean quality and processing methods can cause deviations from theory, and ultimately the real sensation on the palate should be the basis for judgment. [more…]

In the world of pour-over coffee, over-extraction is a topic every enthusiast inevitably encounters. Off-flavors, burnt bitterness, and astringency—these unpleasant taste experiences are often blamed on over-extraction. But not all negative flavors stem from over-extraction—coffee that is too strong can also bring a bitter, intense sensation. So what exactly is true over-extraction? Is the 22% extraction ceiling given by the Golden Cup extraction theory absolute? And how do pour-over parameters like water temperature and grind size shape the final flavor direction? This article will break down the causes of over-extraction and the underlying logic of pour-over extraction one by one, helping you control every cup of coffee more precisely. [more…]

In the world of hand-brewed specialty coffee, the extraction state of a cup directly determines its flavor expression. Some people prefer floral and fruity notes, while others are drawn to dark chocolate and nutty tones, but when faced with astringent sourness or burnt, bitter off-flavors, most people can agree—this cup was not brewed well. Under-extraction, over-extraction, and ideal extraction—these three states correspond to different parameter logics. Starting from the order in which flavor compounds are released, this article will teach you how to judge the extraction situation through clues such as flavor performance, brewing time, and the state of the coffee bed, and offer adjustment approaches for different scenarios including light roasts, dark roasts, and excessive fines, helping you more precisely master every cup of pour-over. [more…]

In the world of coffee extraction, time is a seemingly simple yet extremely critical variable. Different brewing methods have different time requirements, and because espresso has extremely high extraction efficiency, its sensitivity to time far exceeds other methods—even a difference of just 3 seconds can make the flavor in the cup completely different. This article will discuss espresso extraction time, tracing the evolution from the traditional 20–30 second approach to the modern recommended 25–30 second approach, analyzing how time assists in dialing in the grind, judging flavor trends, and verifying extraction stability, and explaining why light-to-medium roasts or large dose scenarios require appropriately extended extraction times. [more…]

The Golden Cup extraction is a concept often mentioned in coffee circles. It uses two indicators—concentration and extraction yield—to judge whether a cup of coffee has been properly extracted. This theory can be traced back to 1952, when it was developed through collaborative research by the American coffee association and Dr. Lockhart of MIT. After multiple revisions, the Golden Cup range currently recognized by the SCAA is: extraction yield 18%-22%, concentration 1.15%-1.35%. But the Golden Cup numbers are only a reference tool, not an absolute formula for brewing delicious coffee. This article will walk you through the origins and development of Golden Cup extraction, the meaning of concentration and extraction yield, how to calculate extraction yield using formulas, and why you should not be limited by the Golden Cup range. [more…]

Many coffee enthusiasts encounter the term "high concentration, low extraction" when reading Front Street Coffee articles or others' brewing分享, but the explanations they find are often packed with confusing data. This article breaks down this complex theory into plain, easy-to-understand descriptions: first, it explains that high concentration, low extraction is not a fixed technique but a brewing concept and outcome; then, with the help of the Golden Cup extraction chart, it clarifies the two core concepts of "concentration" and "extraction yield"; finally, it explains why, when dealing with dark-roasted, anaerobically processed, or extraction-sensitive beans, one needs to lower the extraction yield while increasing concentration, and how this concept is specifically reflected in Japanese-style brewing. [more…]

In coffee brewing, how to balance flavor and avoid under-extraction or over-extraction is a concern for every coffee enthusiast. The Golden Cup standard provides a widely recognized reference framework, covering the ideal ranges for extraction yield and concentration. This article will systematically review the origins of the Golden Cup standard and the specific values set by coffee associations in various countries, explain in detail the formulas for calculating concentration and extraction yield, and, using the example of Front Street Coffee's Ethiopia Florque 4.0 pour-over, demonstrate how to measure and calculate extraction yield with an ExtractMoJo refractometer, helping you find the flavor balance point that suits you in your daily brewing. [more…]

The Golden Cup extraction system is a quality reference framework widely recognized in the global coffee industry, and its core lies in controlling the concentration and extraction yield of the coffee liquid within a specific range. Compiled by FrontStreet Coffee, this article systematically reviews the origins of the Golden Cup standard and the differences in national standards, explains in detail the formulas for extraction yield and concentration, and uses a VST refractometer and a brewing example with Ethiopia Huakui 4.0 to demonstrate how to measure concentration and calculate extraction yield. At the same time, the article also discusses the influence of the pour-over coffee grounds-to-water ratio on flavor, gives a recommended ratio of 1:15 suitable for most bean varieties, and helps coffee enthusiasts build a quantifiable approach to brewing adjustments. [more…]

Should brewing coffee rely on feeling or on data? With the maturation of extraction theory, pour-over coffee has gradually moved from empiricism toward a scientific approach. As a classic reference, the Golden Cup extraction standard, although some of the ranges in its 1.0 version are no longer fully suited to the present, still leaves behind extraction yield and concentration calculation formulas that remain practical today. From Front Street's perspective, this article first reviews the background of the Golden Cup standard and Lockhart's research journey, then focuses on explaining two methods for calculating extraction yield: the traditional dry weighing method, and the method of using a TDS meter to infer extraction yield from concentration. The article also summarizes the definitions of concentration and extraction yield, their interrelationship, and conversion formulas, and reminds that for drip coffee, the water absorbed by the coffee bed requires correcting the weight of the brewed liquid, helping you more accurately evaluate the performance of a cup of pour-over. [more…]

During coffee extraction, many enthusiasts try to judge the extraction state by observing changes in the color of the coffee liquid—the so-called "reading the color" method. Does this method have any scientific basis? Can it accurately distinguish between under-extraction and over-extraction? Front Street Coffee, based on practical testing, found that the color of the coffee liquid does indeed become lighter as extraction progresses, because the acidic and sweet substances among the solubles have smaller molecules and dissolve more quickly, while the bitter substances have larger molecules and dissolve more slowly. Once the acidic and sweet substances have largely dissolved, the bitter substances are still being released, and the coffee liquid begins to take on a whitish hue, which is usually regarded as a signal of approaching over-extraction. However, this method is greatly affected by factors such as flow rate and roast level, and is only suitable as an emergency reference; stable output still needs to rely on measuring tools such as an electronic scale. [more…]

Front Street Coffee has always emphasized that the extraction parameters for pour-over coffee have a significant impact on the cup, and for espresso the impact is even greater. You should know that factors such as the concentration and extraction time of espresso are more demanding than those of pour-over coffee, and the slightest [more…]

Extraction is the core stage of pour-over coffee, but many enthusiasts are often troubled by under-extraction and over-extraction. Starting from the basic principles of extraction, this article explains the standard range of the Golden Cup extraction and provides a detailed comparison of the specific flavor and mouthfeel manifestations of these two imbalanced states. It then addresses common issues such as excessively long brewing time, improper pouring force, and the influence of dripper material, offering actionable adjustment suggestions one by one, including grind size corrections, water stream control, and fine-tuning of water temperature, to help you achieve a balanced and delicious cup of coffee more consistently in your daily pour-over brewing. [more…]

In the practice of pour-over coffee, under-extraction and over-extraction are two common yet frustrating situations. The former makes coffee sour, astringent, and thin, while the latter brings burnt bitterness and off-flavors. To solve these problems, one must first understand the principles of extraction—the process in which water passes through the coffee grounds and dissolves out flavor compounds. The ideal "Golden Cup" extraction requires concentration to fall between 1.2 and 1.4 TDS, with an extraction yield maintained at 18% to 22%. Exceeding or falling short of this range corresponds to over-extraction and under-extraction, respectively. This article will analyze the causes one by one from aspects such as coffee bean selection, brewing duration, pouring technique, and dripper material, and provide specific adjustment suggestions to help you achieve a balanced flavor more consistently in pour-over brewing. [more…]

The same coffee beans, brewed with a different extraction device, can taste completely different in the cup. Coffee extraction paths can be broadly grouped into two types: percolation and immersion. The most fundamental difference between them lies in the speed at which flavor compounds diffuse into the water. In percolation, because fresh water is continuously poured in and the coffee liquid is drained away, the concentration gradient is large and extraction is fast, which easily amplifies the beans' distinctive aromas. In immersion, the coffee grounds sit still in hot water, so the concentration gradient gradually shrinks and diffusion slows down, allowing the coffee's original character to be presented in a more balanced and complete way. Starting from the principles and combined with an analysis of flavor dissolution concentration, this article will help you judge whether the beans in your hands are better suited to pour-over or siphon, and offer specific selection advice. [more…]