Why Water Quality Matters in Pour-Over Coffee (Alkalinity, Hardness & Flavor Explained)

 The coffee we drink is, at its core, water that has dissolved the flavorful compounds inside coffee grounds. In fact, more than 98% of a cup of pour-over coffee is water.

We spend so much time chasing the best origins and growing regions, the most suitable processing methods, the perfect roast profiles, and the most precise brewing techniques—yet all of these efforts ultimately rely on water to carry the coffee’s flavor. If we overlook the foundational role of water, everything else can easily fall apart.

**No.1

Water Plays Two Core Roles in Coffee Brewing: Extraction and Flavor**

Water is responsible for extracting soluble flavor compounds from coffee grounds, and it also makes up the body of the final beverage itself. The chemical composition of the water directly influences what ends up in your cup.

**No.2

The Soluble Compounds in Water: Alkalinity and Hardness**

Water contains both negatively charged ions and positively charged ions.

• The concentration of negatively charged ions determines total alkalinity

• The concentration of positively charged ions determines total hardness

1. Total Alkalinity — Mainly Bicarbonate Ions

Bicarbonate ions act as a buffer in brewing water, helping neutralize acidity and keep the pH within a suitable range. The higher the bicarbonate content, the higher the alkalinity, and the stronger its ability to suppress acidic compounds in coffee.

When alkalinity is too high, it can neutralize or even mask coffee’s pleasant natural acidity, making the cup taste dull, flat, or even slightly “soda-like,” while amplifying bitterness and reducing clarity.
When alkalinity is too low, buffering capacity weakens, causing acidity to become sharp, aggressive, and lacking roundness.

2. Total Hardness — Calcium and Magnesium Ions

Calcium and magnesium ions are highly effective at binding to coffee’s flavor compounds—especially desirable acids, sweetness, and oils. Without them, extraction efficiency drops significantly.

Magnesium is particularly good at extracting floral and fruity aromas, while calcium contributes more to body and mouthfeel. This is why some high-end brewing waters carefully adjust the calcium-to-magnesium ratio.

If hardness is too high (>150 ppm as CaCO₃), coffee tends to extract excessive bitterness and astringency, loses vibrancy, and forms scale on equipment.
If hardness is too low (<50 ppm as CaCO₃), the coffee tastes hollow, thin, overly acidic, and lacking sweetness and body.

According to the Specialty Coffee Association (SCA), recommended ranges are:

• Alkalinity: 40–75 ppm

• Total hardness: 50–175 ppm

  

**No.3

pH: Another Critical Water Parameter**

The SCA recommends a brewing water pH between 6.5 and 7.5, with an ideal target around 7.0.

pH measures acidity and alkalinity. Brewing coffee with alkaline water (pH above 7) reduces perceived acidity—the higher the pH, the stronger the buffering effect. Simply put:

• Higher pH → lower perceived acidity

• Lower pH → higher perceived acidity

However, higher alkalinity is not always better. Excessively alkaline water often leads to bitterness and astringency, dulling the coffee’s character.

**No.4

How to Create Better Brewing Water**

1. Test Your Water

Use a TDS meter or a dedicated water testing kit to understand your current brewing water.

2. Choose a Solution

(1) Basic Option: Filtered Water
Activated carbon filters remove chlorine, odors, and organic compounds, improving taste. While they have limited effect on hardness, they’re a solid starting point for most homes and cafés.

(2) Intermediate Option: Bottled Water Blending
Mixing low-mineral purified water with mineral water at specific ratios is an affordable and effective way to improve brewing water.

(3) Professional Option: Custom Brewing Water
Using third-party mineral packets or an RO (reverse osmosis) system with remineralization filters allows precise control. Many competition brewers use this approach to tailor water for specific coffees.

Water quality is one of the most underestimated variables in pour-over coffee. When we care about origin, processing, roast profiles, and brewing techniques, we should also care about the water we use—because that’s often the final key to unlocking a truly exceptional cup.

How to Brew a Clean Cup of Coffee | Pour Over Tips for Maximum Clarity

 There are many reasons why we might fall in love with a cup of coffee. It could be its rare and complex flavor profile, a rich and weighty mouthfeel, layered and evolving notes, or even the story behind where it comes from. Beyond these, there are also some more niche reasons. For example, I have quite a few friends who judge a coffee by one key word: “clean.”

Here, “clean” doesn’t mean visual clarity, nor does it mean a coffee with low flavor complexity or “nothing going on.” Instead, it refers to a cup that is free of any unpleasant off-flavors, with flavors that are well-defined and easy to distinguish. It may sound simple, but achieving this level of cleanliness actually places very high demands on coffee quality. From growing and processing to roasting and brewing—in short, every step from seed to cup needs to be handled with great care.

Before the concept of specialty coffee became widespread, exported green coffee was often processed in rough, unsophisticated ways by local farmers. As a result, it was common for coffee to carry undesirable flavor defects. In the old version of the SCAA flavor wheel, there was even a dedicated section known as the “negative flavor wheel.”

So what is the negative flavor wheel? It refers to flavors that are universally recognized as unpleasant—defective notes that make coffee uncomfortable to drink. As mentioned earlier, these defects can arise at many stages along the coffee chain. For example, when unripe beans are mixed in, the brewed coffee may exhibit grassy or hay-like flavors, usually caused by harvesting underripe cherries. Poor control during processing can lead to mold or over-fermentation, resulting in musty or moldy notes. Uneven roasting can cause scorching, producing smoky flavors, while underdeveloped roasts may bring out dry, hay-like characteristics.

Beyond outright defects, extraneous flavors also play a role in perceived cleanliness. These are flavors that detract from clarity. They include defects, but are not limited to them. For instance, imagine tasting a coffee whose main profile should be berries and citrus, but you also find notes of nuts, cocoa, or toasted bread mixed in. While these aren’t necessarily negative flavors on their own, when they appear in a fruit-forward coffee, they can make the cup feel cluttered and unfocused—like a room filled with good furniture, but arranged in complete chaos. This, too, is a sign of insufficient cleanliness.

With the arrival of the specialty coffee era, people at every stage of the supply chain have begun to prioritize quality. Fully ripe cherry harvesting has become standard practice in most producing regions, and processing techniques have grown increasingly refined. As a result, many undesirable flavors are eliminated right at the source. For us as end consumers, choosing a reliable roaster (for example… me—I’m very reliable) means that our attention can largely shift to the final step: brewing. With green buyers and roasters acting as multiple layers of quality control, it’s unlikely that truly poor-quality beans will end up in our hands.

That said, don’t underestimate the importance of brewing. Proper extraction is crucial to a coffee’s cleanliness. In most cases, when a cup lacks clarity and is filled with muddled flavors, the culprit is improper extraction. In pour-over brewing, for example, excessively high water temperature, overly fine grinding, overly long brew times, or aggressive pouring and agitation can all lead to over-extraction. This causes large bitter compounds to be released in excess, masking the coffee’s natural flavors with woody, harsh bitterness.

In addition, factors such as dirty brewing equipment with residual oils, filter papers with strong papery flavors, or coffee that is too fresh and carries a “green” or restless sharpness can all introduce unwanted notes and reduce clarity. So it’s not just about extraction parameters—every small detail during brewing needs to be carefully controlled. Only then can we brew a truly clean cup of coffee.

Generally speaking, if you start with high-quality beans and use reasonable extraction parameters, your coffee will almost always display excellent clarity. If you’d like to experience a particularly clean cup, I recommend trying two coffees from my lineup: Esmeralda Estate · Washed Green Label Geisha and Ethiopia · Natural ALO. Brew them with a water temperature of 92°C (198°F), a brew ratio of 1:16, an extraction time of 2:00–2:20, and a grind size where 75–80% passes through a #20 sieve.

With these parameters, you’ll get a beautifully clean cup. The former offers clearly defined notes of citrus, jasmine, and green tea, while the latter expresses mango, pineapple, and magnolia. Both are driven by bright acidity and gentle sweetness, with a silky, cream-like mouthfeel and a clear, uplifting sense of clarity.

Why 1:16 Is the “Golden Ratio” for Pour Over Coffee (And When to Use 1:15 Instead)

 After customers buy coffee beans in the shop, they often ask me about recommended brewing parameters—water temperature, grind size, and, of course, the coffee-to-water ratio.

Whenever I mention a ratio of 1:15, some people are surprised. That’s because most cafés on the market tend to use 1:16 when brewing pour-over coffee. Just yesterday, someone said to me, “I see everyone using 1:16. I thought that was the best—like the golden ratio for pour-over.”

And to be fair, from a certain perspective, 1:16 really can be called a golden ratio.

We know that coffee contains a limited amount of soluble material—only about 30% of the bean’s weight. Based on this fact, Dr. Ernest Lockhart conducted a series of studies and found that the coffees most people enjoy tend to fall within a specific range of strength and extraction:

• Total Dissolved Solids (TDS): 1.15%–1.35%

• Extraction Yield: 18%–22%

  

Any brew that lands within this range is known as a Golden Cup extraction, and the coffee itself is referred to as a Golden Cup coffee.

From these findings, the Golden Cup Brewing Chart was created. This chart illustrates the relationship between brew ratio, strength, and extraction yield. Simply put, it shows which coffee-to-water ratios make it easiest to brew a Golden Cup. And 1:16 happens to be one of the ratios that reliably produces a coffee with both pleasant strength and extraction. That’s why it has earned the reputation of being the “golden” ratio.

However, as I’ve always emphasized, the Golden Cup concept is a reference—not a rulebook. A coffee that falls within the Golden Cup range isn’t guaranteed to taste good, and a coffee outside of it isn’t automatically bad. The same logic applies to brew ratios.

Brew Ratio Is About Concentration

The primary role of the coffee-to-water ratio is to determine coffee strength. When extraction yield is similar:

• A larger ratio (less water) produces a stronger, more concentrated cup

• A smaller ratio (more water) results in a lighter, more diluted cup

Since everyone’s taste preferences are different, the “golden ratio” is different for each person.

For example:

• If you prefer a lighter, easier-drinking coffee, ratios like 1:17–1:20 may suit you better.

• If you enjoy higher concentration and more intense flavors, ratios such as 1:14, 1:10, or even an espresso-style 1:2 brew ratio may be more appealing.

  

Why I Personally Use 1:15

I choose 1:15 because it produces a slightly higher concentration, allowing the flavors to feel more focused and expressive. This makes it easier to identify the coffee’s unique characteristics.

In addition, higher concentration improves mouthfeel, giving the coffee more body and structure. I personally enjoy this richer texture. That said, a good cup of coffee isn’t determined by brew ratio alone. It must work in harmony with other variables to achieve a balanced extraction.

My Typical Brewing Approach

In most cases, I start with a 1:15 ratio and adjust other parameters based on the roast level.

For light to medium-light roasts, such as Ethiopian Gesha Village–style coffees or Panama Boquete Gesha, I typically use:

• Water temperature: 92°C (198°F)

• Grind size: 75%–80% passing a #20 sieve (similar to fine sand sugar)

• Brew time: around 2 minutes

This combination yields a cup with both ideal strength and extraction, clearly showcasing floral aromas and fruity notes.

For darker roasts, such as Brazil Fazenda Rainha or Sumatra Golden Mandheling, I lower the parameters slightly:

• Water temperature: 88°C (190°F)

• Grind size: 70%–75% passing a #20 sieve (coarser than the above)

• Ratio and brew time: same as before

This results in a coffee with pronounced chocolate, hazelnut, and caramel notes, along with a noticeable and pleasant sweet aftertaste.

Final Thoughts

In the end, it’s simple:
If you enjoy the way your coffee tastes, then that ratio is your golden ratio.

That’s all there is to it. ☕

Why Japanese Coffee Lovers Prefer Flannel Filters Over Paper

 When it comes to flannel filters, many coffee lovers may have only seen them in Japanese movies or through videos by Japanese baristas. Compared with the common paper filter and dripper combo, the flannel filter is far less popular outside of Japan. Most people’s first encounter with it comes from Japanese coffee culture itself.

That naturally raises the question: why do Japanese people love brewing coffee with a piece of flannel cloth? What makes coffee brewed with flannel so different from coffee filtered through paper?

What’s Special About Flannel Filters?

If you’ve read my posts before, you’ve probably seen me mention this: flannel filters produce coffee that’s richer and more aromatic. The reason is simple — flannel doesn’t filter out oils and insoluble compounds as thoroughly as paper does.

Flannel is a soft, fuzzy fabric that originated in Wales, England. Since its invention, it’s been used in countless applications thanks to its versatility. As a coffee filtration tool, flannel can actually be traced back to the 17th century — before paper filters even existed. At that time, people in Europe used flannel cloth to strain brewed coffee. However, it wasn’t until hand-brewed coffee spread to Japan that flannel filters were truly adopted as a brewing tool rather than just a strainer.

Compared to paper filters, flannel has larger fiber gaps, which allow coffee oils and fine insolubles to pass through. Coffee oils contain fat-soluble aromatic compounds that give the brew a fuller, richer fragrance. Those oils and insolubles also enhance the body, making the coffee feel smoother and more rounded on the palate. That’s the main reason flannel-brewed coffee is so beloved.

Flannel Filter Types and How They’re Used

A flannel filter typically has two sides — one fuzzy (the “nap” side) and one woven (the “cotton” side). The nap feels soft and smooth to the touch, while the cotton side feels slightly coarse due to the weave texture.

Both sides can be used to hold coffee grounds, but most people — myself included — prefer to place the cotton side inside and keep the fuzzy nap side facing outward. Why? Because coffee grounds tend to cling to the nap, making cleaning much more difficult.

Flannel filters are usually attached to a special metal handle. You can hold it in your hand while pouring, or hang it directly over a server like a regular dripper. Most people choose the latter for both the convenience and the ritualistic charm it brings.

How to Brew Great Coffee with a Flannel Filter

Brewing with flannel isn’t much different from using a dripper and paper filter in terms of parameters. However, if you’re hand-holding the flannel rather than placing it on a server, you’ll need to adjust from a coffee-to-water ratio to a coffee-to-liquid ratio, since the scale only measures the liquid dripping out of the cloth.

When using a flannel filter, I prefer deep-roasted beans, as the characteristics of flannel naturally complement darker roasts. For this example, I used a deeply roasted Sumatra PWN Golden Mandheling.

Brewing parameters:

• Coffee dose: 20g

• Coffee-to-liquid ratio: 1:13 (equivalent to 1:15 coffee-to-water)

• Water temperature: 88°C (190°F)

• Grind size: EK43 at 10.5, with 70–75% passing a 20-mesh sieve (a bit finer than usual hand pour)

• Pouring method: three-stage pour

Since we can’t see the total water volume when using flannel, the bloom stage is done simply by wetting all the grounds — not by adding double the coffee weight as usual. Start by pouring hot water into the center, then slowly move outward in circles until all grounds are evenly wet. This prevents channeling. Let it bloom for 30 seconds.

After blooming, pour with a steady stream, slowly spiraling from the center outward and back in again, repeating the motion until the water level nearly covers the coffee bed. Wait for it to draw down before starting the next pour.

During the third pour, focus your flow on the center of the bed, keeping your pouring circle within the size of a coin. Once you reach your target yield — in this case 260ml (based on 20g coffee and a 1:13 ratio) — remove the filter and stop pouring. Total brew time: 2 minutes and 21 seconds.

Comparing Flannel and Paper Filter Brews

I also brewed the same coffee using a Kono dripper with paper filter, under the same parameters, to compare. The flannel-brewed cup was noticeably more aromatic, smoother in texture, and had a longer aftertaste — though the differences were subtle unless tasted side by side.

Flavor-wise, both cups expressed the Mandheling’s signature notes of chocolate, nuts, pinewood, and spice, but the paper-filtered version was cleaner, while the flannel version offered a fuller body and deeper richness.

Why Flannel Isn’t Commonly Used in Cafés

You might be wondering — if flannel can produce such wonderful results, why don’t more cafés use it?

The answer is simple: flannel filters aren’t disposable. They require thorough cleaning and sanitizing after each use to maintain quality and hygiene. Compared with paper filters that you can toss out after brewing, flannel takes significantly more effort to maintain.

That’s why even in Japan, many baristas and home brewers now prefer the convenience of paper filters.

Still, both methods have their strengths. Flannel gives you aroma and body; paper gives you clarity and cleanliness. There’s no absolute winner — it all comes down to personal taste and the kind of coffee experience you want.