When making espresso, hot water does not always pass evenly through the coffee puck—when the flow breaks through along paths of least resistance, the so-called "channeling" occurs. This phenomenon causes some coffee grounds to be over-extracted, releasing off-flavors, while other areas are under-extracted, ultimately throwing the strength and flavor of the entire cup out of balance. Channeling is especially prone to occur in espresso extraction, because the extreme conditions of high temperature and high pressure demand extremely high uniformity in the coffee bed. Although we cannot directly observe the state of the water flow during extraction, the holes on the surface of the puck and the spatter during extraction can both provide clues for diagnosis. This article will systematically explain the causes of channeling, how to identify it, and share Front Street Coffee's practical advice on optimizing distribution. [more…]

Peru, a South American coffee-producing country, has recently been hit by a series of natural disasters and environmental crises. The Sabancaya volcano in the south has entered an orange alert level, and ash from frequent eruptions is severely affecting nearby farms and pastures; meanwhile, the provinces of Huancavelica and Cusco have been declared in a state of environmental emergency due to heavy metal mercury contamination. Both regions have coffee cultivation, and mercury contamination not only inhibits crop growth and reduces agricultural product quality, but may also trigger labor shortages. The Peruvian government has already launched response measures, but concerns within the industry about coffee production and quality are rising. [more…]

Grind size is the most difficult part of pour-over parameters to master. Front Street Coffee uses an 80% pass rate through a No. 20 sieve as a beginner-friendly calibration baseline, but different grinders vary enormously in performance, and the same sieve pass rate can produce drastically different flavor outcomes. This article centers on grind calibration: it first explains the limitations of the sieve method and the particle size distribution characteristics of uniform grinders such as the EK43s, then offers remedies for poor-quality grinders, including hand grinder RPM control, the pull-back technique for staged grinding, and the direction for adjustment when too many fines cause off-flavors. Finally, it discusses the criteria for deciding whether sieving is necessary and the practical technique of a single-pour flush to wash away fines, helping you find the grind parameters that suit you. [more…]

On the same grinder at the same setting, why does switching to a different coffee bean produce noticeably different grind sizes? This actually comes down to two core physical properties of coffee beans—density and brittleness. Density is determined by growing altitude: the higher the altitude and the slower the growth, the harder the bean and the fuller the flavor. Brittleness, on the other hand, is directly tied to roast level: the darker the roast and the more moisture is driven off, the looser the structure and the easier the bean is to crush. Starting from actual experiments at Front Street, this article uses a comparison of the sieve-passing rates of dark-roasted Mandheling and light-roasted Yirgacheffe to explain why grind consistency breaks down, and how that leads to clogged filter paper and over-extraction problems. [more…]

In the three-pour method for pour-over coffee, the timing of the third pour is often overlooked—should you wait for the coffee liquid to completely drain before pouring, or should you top up promptly once the water level drops by half? Front Street Coffee conducted two sets of comparative experiments, using Costa Rica Strawberry Candy and washed Yirgacheffe beans respectively, to analyze in depth the practical differences between the two pouring methods from the dimensions of aroma, flavor, extraction time, and coffee bed state. The experiments revealed how the timing of the pour affects the temperature of the coffee bed, fine migration, and the final flavor performance, while also explaining why beans of different hardness show completely different results when faced with waiting for the liquid to drain. This article will present the full experimental process and conclusions to help coffee enthusiasts understand the core logic of judging when to pour in the three-pour brewing method, and provide Front Street's practical recommendations. [more…]

When using an espresso machine to extract espresso, many people have encountered the situation where the puck sticks firmly to the brew head. Once the puck falls off, it not only tends to crumble into the drip tray, but is also quite troublesome to clean up. Some people therefore believe that the coffee's flavor will become worse, but is that really the case? Front Street, based on an actual encounter, tasted the coffee extracted while the puck was stuck and analyzed the various operational factors that lead to this phenomenon, including the dose, the timing of removing the portafilter, and bumping before extraction, to help everyone more clearly understand the real reasons why the puck sticks to the brew head. [more…]

When extracting espresso, many coffee enthusiasts strive to knock out a complete puck. Although whether the puck is complete does not directly determine the flavor of the coffee, it can indirectly reflect whether the extraction process is standardized. The formation of the puck is closely related to operations such as distribution and tamping, and these steps are precisely the key to affecting coffee quality. Based on the practical experience of Front Street Coffee, this article explains in detail how to reduce channeling by choosing an appropriate dose, distributing the grounds evenly, and tamping correctly, ultimately obtaining a complete puck and thereby increasing the chances of making delicious coffee. [more…]

The extraction quality of espresso can be judged not only by flow rate, pressure, and time—the puck after extraction also reveals a great deal of key information. An ideal puck should be dry and level, structurally intact, and uniform in color. In practice, however, problems such as cratered surfaces, holes, standing water, loose structure, one half dry and the other half wet, or even a blackened bottom are all too common, and they often point to deviations in dose, grind size, distribution technique, or equipment pressure. This article systematically sorts out the manifestations and causes of six common puck abnormalities, offers targeted adjustment plans, and explains how to correct extraction through operations such as grinding finer while reducing dose, or grinding coarser while increasing dose, helping coffee enthusiasts consistently make a qualified espresso at home. [more…]

When making espresso, the puck sometimes sticks to the dispersion screen of the group head. What exactly causes this? And does it affect the flavor of the coffee? This article starts with three common causes and analyzes them one by one: too much coffee grounds, failing to remove the portafilter in time after extraction, and the puck being knocked loose. Front Street will also draw on its own practical experience to explain the possible burnt and bitter taste issues that can arise when the puck comes into contact with the dispersion screen, as well as the impact of channeling on espresso performance, helping you judge in your daily service when there is no need to worry and when you need to adjust parameters. [more…]

Tamping the puck flat is a basic consensus in espresso extraction, but how much force should actually be used to tamp it down has long been a point of disagreement among baristas. Some give the tamper a light spin and apply just a little pressure, while others put their whole body weight into compressing the puck as hard as possible. Front Street conducted a comparative experiment using two grind sizes—coarse and fine—tamping with a regular force of 1.5 kg and a full-force press of about 9 kg respectively, to observe changes in extraction time. The results showed that because coffee grounds differ in density, the force needed to reach a compacted state also varies: fine grinds require greater pressure to be tamped to their most compact state, while coarse grinds are already sufficiently compacted at 1.5 kg, and full-force tamping produces extraction results almost identical to regular force. This article will present the full experimental process and conclusions to help coffee lovers understand the relationship between tamping force and grind fineness. [more…]

Tamping is a seemingly simple yet highly debated step in espresso making. Some people casually rotate the tamper, while others put all their strength into pressing the puck as tightly as possible. Just how much does tamping pressure affect extraction? Does the compactness of the puck really influence flow rate? Front Street Coffee answers these questions through two sets of comparison experiments with different grind sizes, using actual extraction time data. This article will guide you through the subtle relationship between tamping pressure and grind particle size, helping you find the tamping method that suits you best. [more…]

Extracting a qualified espresso shot—the tamping step is often overlooked by beginners, yet it directly affects the integrity of the puck and the final flavor. This article focuses on the correct way to use a tamper, starting from the phenomenon of knocking out an intact puck, and explains how each tamping step affects coffee quality. Whether you are an enthusiast just getting into espresso or a seasoned coffee pro hoping to refine your skills, you can understand why an intact puck can reflect extraction quality, and master the key operational details that make coffee taste better. [more…]

Whether to add a filter paper to a moka pot depends on what problem you're trying to solve. Placing filter paper at the bottom of the basket mainly helps distribute hot water more evenly, reduces clogging, and makes it easier to knock out an intact puck for simpler cleaning; placing it on top of the puck increases filtration precision, reduces off-flavors from fine particles, gives a cleaner taste, and slightly increases extraction pressure. Front Street Coffee ran comparisons using a classic blend and found that adding filter paper at the bottom has very little effect on flavor but offers a clear cleaning advantage. This article explains the principles, practical effects, and suitable scenarios for each placement method, helping you choose according to your needs. [more…]

When pulling espresso, you sometimes remove the portafilter and find a large amount of hot water left in the basket, with the puck wet, even loose and misshapen. This phenomenon not only affects consistency in the cup but also makes it hard to identify the root cause. Starting from the principles of espresso extraction and pressure release, this article systematically breaks down the three common causes of water pooling in the basket: grinding too fine, which impedes the flow of hot water through the coffee bed; using too small a dose, which leaves too much distance between the puck and the shower screen; and insufficient pressure on home machines, which weakens the back-suction effect. It also offers Front Street Coffee's adjustment suggestions to help coffee enthusiasts quickly pinpoint the problem and improve extraction flow rate and puck condition. [more…]

After pulling an espresso shot, the ideal puck should be dry, intact, and come out in one solid piece without crumbling. But in practice, many coffee lovers run into a soggy, muddy puck with standing water at the bottom of the basket. This abnormal phenomenon is usually linked to four factors: grinding too fine, coffee beans stored too long so they lose carbon dioxide, too large a gap between the puck and the dispersion screen, and unstable extraction pressure in the espresso machine. This article breaks down the principle behind each cause one by one and offers corresponding troubleshooting and adjustment methods to help you quickly pinpoint the problem and get back to normal extraction. [more…]

Crafting a perfect espresso is the goal of many coffee enthusiasts. However, in practice, sudden spurting, pinholes, or channeling in the espresso flow often catch people off guard. These phenomena not only affect the uniformity of coffee extraction, but also lead to weakened aroma, a thinner mouthfeel, and even unpleasant flavors such as sharp acidity and bitter burnt notes. This article will take an in-depth look at the causes of channeling, from dosing details, portafilter knocking, dose control, to coffee grounds clumping and more, helping you find the root of the problem and offering practical solutions. At the same time, we will also discuss whether a split portafilter can truly solve channeling issues, and share Front Street Coffee's classic espresso blend recommendation to help you easily improve the quality of your espresso. [more…]

Distributing the coffee grounds is a crucial step in making espresso, directly affecting the extraction and flavor performance of the coffee. This article, from the perspective of Front Street, systematically explains the purpose of distribution, common misconceptions, and correct operating methods. By understanding the flow characteristics of water through the coffee puck and mastering techniques to avoid channeling, it helps coffee enthusiasts improve extraction uniformity and craft a balanced-tasting espresso. [more…]

When pulling espresso shots, have you ever encountered water pooling in the portafilter basket, a loose puck that won't hold its shape, or crema that clumps up quickly with tiger stripes appearing on the surface? Each of these phenomena actually has its own underlying cause. This article continues Front Street's series on common espresso extraction issues, breaking down key variables one by one—dose, grind size, coffee bean degassing, and fines distribution. From judging extraction evenness by puck condition, to understanding the relationship between crema clumping and coffee bean freshness, to clarifying whether tiger stripes really mean over-extraction, this guide helps you troubleshoot more accurately and adjust your parameters, making every espresso shot more stable and controllable. [more…]

Many people new to espresso think that the harder you tamp, the denser the puck becomes, the harder it is for hot water to pass through, and the longer the extraction time naturally gets; conversely, with a light tamp, the puck is loose, the flow is smooth, and the time shortens. This logic sounds reasonable, but what is the real situation? Front Street used the same medium-dark roasted espresso blend, tamping 20g of coffee grounds with 2kg, 5kg, and 20kg of force respectively, extracting at a 1:2 coffee-to-liquid ratio, and the extraction times were almost identical, with no obvious difference in flavor performance either. Why is this so? The core reason is that the 9bar pressure during espresso machine extraction, converted to a 58mm puck, is as high as about 243kg, far beyond what human tamping force can compare to. Even so, tamping force still affects the probability of channeling occurring. This article will combine experimental data to analyze the true relationship between tamping force and extraction, and explain why even tamping is more worthy of attention than hard tamping. [more…]

Using an espresso machine to make espresso, one of the most frustrating problems is that the pressure won't come up—clearly the machine is rated at 9 bar, yet actual extraction always hovers between 5 and 7 bar, and the resulting coffee is thin and sharply acidic. Behind this is actually a close relationship with puck resistance. This article starts from the principles of pressure, analyzes why insufficient puck resistance leads to reduced extraction efficiency, and offers three actionable adjustment directions: grind finer, increase the dose, and increase tamping force. At the same time, combined with the characteristics of beans with different roast levels such as Front Street Classic Blend, Commercial Blend, Huakui SOE, and Natural Red Cherry SOE, it explains how the grind setting should be matched, helping coffee enthusiasts bring espresso extraction back into the normal range. [more…]