To consistently make a delicious Espresso at home or in a shop, relying on feel alone is far from enough—you need to understand and control several key variables. This article breaks down the hardware and operational points that affect espresso quality one by one, from grind uniformity, fixed dose, and tamping technique, to brewing pressure, water temperature, extraction yield, and machine materials. Whether you use a flat burr or conical burr grinder, a vibration pump or rotary pump, you can find practical adjustment ideas here. The article also shares Front Street Coffee's practical advice on equipment selection and parameter settings, helping coffee enthusiasts avoid detours and make every cup of espresso closer to the ideal state.
In the past two years, the number of espresso enthusiasts has grown especially fast—one could say at an unprecedented pace. Here I'd like to organize some of my insights and experiences, skipping the lengthy cultural background and treating this as a technical guide for making a beverage, or cooking a good dish.
1. Coffee grounds need to be fine enough, and as uniform as possible
Espresso extraction relies on relatively high pressure, so the coffee grounds must be ground fine enough. Beyond fineness, you also need uniformity, so that the force on the puck is consistent throughout and extraction is even. This requires a reliably performing grinder. Espresso grinders are mainly divided into two types by burr—flat burrs and conical burrs. The strength of flat burrs is that they ensure grind uniformity. Conical burrs produce grounds made up of particles of varying sizes. Since uniformity is so important, why still use conical burrs? Because conical grinders usually pair with low-speed, high-torque motors, grinding fast and not prone to heating up, so when large amounts of grinding are needed, the advantage of conical burrs shows. Some also feel that although conical-burr grounds aren't uniform enough, they can bring out richer layers; equally, some believe uneven grounds easily draw out off-flavors. So conical burrs themselves are a controversial type—everyone has their own view.
Personally, I don't lean one way toward conical or flat burrs. If it's for personal use, or you don't need to grind large amounts, heat generation can basically be ignored, then I'd recommend a flat burr grinder—stability and uniform grinding are the prerequisites for quality. If it's a commercial setting requiring large amounts of grinding, you should choose a conical burr grinder that grinds faster and doesn't heat up easily. Given the current state of the domestic coffee market, flat burrs as the mainstream is a relatively wise choice.
Burrs are mostly made of high-hardness stainless steel, and now some manufacturers offer ceramic or titanium alloy burrs. Ceramic burrs are less prone to generating high heat, while titanium alloy is more durable—you can upgrade according to your needs.
2. Fix the dose
Fixing the dose and only adjusting grind fineness helps build a habit of stable extraction. This greatly helps with standardization of shop output. For individuals, it also makes it easy to quickly find the right grind setting when switching between different beans. For me, my usual double dose is 16g.
3. Find the tamping force and technique that suits you
Expressing a skill in words always runs into many inconveniences. Tamping is roughly divided into the coarse-grind-heavy-tamp school, the fine-grind-light-tamp school, and the no-tamp school. Whichever school you belong to, you can make perfect Espressos of different styles. The no-tamp school is the most niche and hardest to master, because it takes a lot of effort and time to find the critical point of dose and grind fineness, and it has certain requirements for the grinder. The benefit of no-tamping is that once you find that point, you can avoid failed tamping. But making a cup of coffee has many variables. If you've mastered light and heavy tamping, treating it as a new experience isn't bad either, though here I won't recommend the no-tamp school.
4. Maintain stable brewing pressure
Espresso machines use a pump to generate pressure, roughly divided into vibration type and rotary type. Vibration type is small in size and lower in cost, mostly used in home machines, such as the XX coffee machine, with a nominal pump pressure of 15bar or 19bar, meaning the pump pressure peak can reach a maximum of 15bar or 19bar, but it doesn't stay stable at one value—it fluctuates between 1 and 15bar. This is one of the reasons home machines make coffee with more off-flavors. Similarly, this is another basis for why I don't think conical burr grinders can bring deep-level flavors—if this logic holds, wouldn't the unstable pressure of a vibration pump also bring different layers of flavor? In brewing, the lower the controllability, the worse the stability of taste.
Rotary pumps, because of their larger size, are mostly used in commercial machines and high-end professional home machines, and can stabilize pressure within a fixed value. Intuitively speaking, the pressure curve of a vibration pump is erratic, while the pressure curve of a rotary pump approaches a straight line—the two are not on the same level. Using a rotary pump is a major factor in stable extraction. In addition, rotary pumps are much quieter than vibration pumps. Some vibration pumps are extremely noisy, giving an unsafe, cheap feeling, and noise affects mood, so I don't recommend using a vibration pump coffee machine as a business machine.
Currently, regarding espresso brewing theory, there's the 9±1 standard, as well as 9±0.5 and 9±2 versions. For ease of memory and understanding, I personally set it at 9.
5. Stable brewing water temperature
The higher the brewing water temperature, the weaker the coffee's acidity and the stronger the bitterness and burnt flavor; the lower the water temperature, the higher the acidity and the lower the bitterness and burnt flavor. So you should adjust the ideal water temperature according to different beans and recipes—for example, use lower temperature for dark roasts and higher temperature for light roasts. My most commonly used water temperature is 91 degrees.
In terms of water temperature control, most home machines, because they use heating blocks or smaller boilers, have difficulty stabilizing water temperature, with temperature differences reaching 10 degrees during extraction. Even if the operator is very careful, they cannot overcome this hardware bottleneck. Large mainstream commercial machines (heat exchange type) also have a 4 to 8 degree temperature difference, demanding quite a lot of operator control. For dual-boiler and multi-boiler systems with independent PID temperature control, temperature is easy to stabilize. The Expobar dual boiler I use can keep the temperature difference during a cup of Espresso extraction to only 0.5 degrees. Higher-end coffee machines like Synesso, Slayer, etc., can control temperature within 0.1 degrees, and the human palate's resolution limit for temperature effects is about 0.3 degrees, so 0.1 degree temperature control is already perfect for humans.
6. Fix the extraction yield
The more variables we control, the higher the probability of getting a good cup of coffee.
Although you can judge whether to continue or stop extraction based on the state of the coffee flowing out, breaking through the theoretical framework requires enough brewing experience. At the beginning, giving yourself a stable framework is more practical.
Widely applied extraction yields:
Single Espresso: extract 25-35ml of coffee in 25 to 30 seconds
Double Espresso: extract 45-55ml of coffee in 25 to 30 seconds
7. Overall good heat-conducting materials
Among the coffee machine hardware we often discuss, the most commonly mentioned are boiler size and pump. Actually, there are many more things to pay attention to in a coffee machine—different materials, piping design, etc., all affect the result of a cup of coffee. This is also why responsible manufacturers use copper or stainless steel as the main material for coffee machines. First, copper has good thermal conductivity (ensuring uniform and stable temperature) and ductility, and even under frequent alternating hot and cold, it's not prone to metal fatigue. Stainless steel, on the other hand, is more hygienic and durable. Because stainless steel as a material appeared relatively late, many manufacturers still use traditional copper to make coffee machines. Materials like plastic and aluminum are completely unreliable, though they're commonly used in home machines because they're cheaper.
The above points are all summaries of my personal experience, in no particular order. To get a perfect Espresso, you may have to put in more effort than you can imagine, but in the end you'll harvest more fun and delicious coffee.
The above content is compiled by CoffeeHunters, a coffee news website.
