Coffee School
Tips, tricks and knowledge from years of chasing coffee excellence
The Basics
101: Grinding
Great coffee starts with a consistent grind. Coffee is ideally ground right before brewing, because the moment you break the bean's surface, the volatile aromatics that define specialty coffee start to fade.
The grind also needs to match the brewing method. Too coarse and you'll under-extract... thin mouthfeel, weak cup, missing flavors. Too fine and you'll over-extract... bitter, harsh, overwhelming. Inside that range is your cup.
How do you know what's right? There are guidelines, but there's also real room to experiment because specific brewers and filter types behave differently.
Burr grinders (conical or flat) are the best choice for consistency. Blade grinders work too, though they're harder to control. If you have a blade grinder, try a pulse method... one second on, one second off, eyeballing the particle size as you go.
The basic guidelines:
Cold brew and French press: coarse grind.
Drip maker and pour-over (paper filter): medium-fine, slightly past the center setting on most grinders.
Espresso and Turkish coffee: very fine. Not every grinder is built to handle this end of the spectrum.
Be on the lookout for some of our favorite & recommended grinders featured in the Hardware section of the shop
100: Philosophy of the Brew
Our coffee ritual aims to result in a tasty, compelling beverage which inspires us. Jerry Seinfeld goes so far as to say “I think coffee is the most important part of a human's life”. I’m not going to argue with the likes of Jerry Seinfeld!
On a physical and chemical level, we grind coffee beans and brew them to extract an array of both simple and complex chemical compounds that interact with most of our senses. We make an extraction with water which fills our cup. There are so many ways to accomplish this task so we’re going to make sense of the process so you can increase your confidence in making your next cup and enjoyment not only of the coffee itself but also the process. We find that the ritual of making the coffee is also part of the enjoyment of the coffee. We also encourage experimentation and finding the ritual that’s best for you. We’re not here to dictate “right” and “wrong”, only to offer guidelines and knowledge based on our own experience and some science too. We’ll divide the process in several main topics: Grinding, Water, Brewing, Coffee Storage
102: Water
Most of your coffee is water meaning that it’s critical to the taste of your coffee. Despite this, water is a sometimes overlooked portion of the home coffee brewing exercise. There are two main components to consider when it comes to your coffee: Water temperature and water quality
Water temperature: This is the variable with which most of us getting into the details of brewing coffee are most familiar. Brewing temperature of the water must be between 195 - 205 degrees Fahrenheit. The water temperature directly impacts the level of total extraction. There’s plenty of room to experiment here but you can also reliably keep things in a tight range once you set a baseline.
Water quality: Municipal water in most of the country has a decent baseline, but Colorado and most of the West run hard, with meaningful dissolved minerals our treatment plants don't remove. Add chlorine on top of that and you're brewing through both flavor noise and chemistry interference.
Some of those dissolved minerals actually help extraction. Others get in the way. A basic single-stage filter like a Brita removes chlorine but leaves the mineral content untouched, which is fine for casual brewing. For more serious brewing, dedicated brewing water products give you a controlled starting point.
One practical note: hard water is tough on your equipment over time. If you're brewing daily, an unfiltered kettle or machine will eventually scale up. Filtering at minimum extends gear life.
103: Brewing
This is where we turn the beans into a brewed coffee. There are three basic concepts of brewing: Drip, Immersion, & pressure. All three have variations within them and can range in investment from very small ($20 or less) to very high (many thousands of dollars). Different coffee preparations & history are associated with the three different styles. It can be fun to experiment with how the same coffee can have different flavor profiles depending on which brew method you employ.
Drip AKA “percolation” & “pour over” is where water flows over and through the ground coffee to create an extraction. This is what a traditional countertop coffee maker and pour over style accomplish. These are some of the most convenient methods of making coffee due to their clean up and ease of use (when using automatic machines). Manual pour-over takes some technique and practice, though the upside is real control over the cup.
Immersion, like tea, is where the water fully immerses the ground coffee for a period of time and is then filtered out separating the brewed coffee and spent grounds. The most familiar of these methods may be the French Press which can be very affordable, forgiving and really emphasize the body in the final cup.
Pressure methods, like espresso, combine heat and pressure to maximize the extraction making a concentrated brew that can then be combined with milk (or milk alternatives) for Italian Cafe-style beverages (Latte, Cappuccino, Cortado, etc.) or diluted with hot water to mimic a drip-style coffee (Americano) but retain the full flavor profile of the extraction. Stovetop espresso makers like the Moka Pot are affordable and relatively easy to use. Stand alone espresso machines can vary greatly in cost, effectiveness & simplicity.
Scale. No matter what brew method you prefer, we recommend using a scale that measures in grams down to the 10th of a gram. Many kitchen food scales will work for this but there are dedicated pour over coffee scales with additional features… Several inexpensive options are on the market now too. Measuring coffee or water by volume (scoops & oz/ml) isn’t consistent since different coffee has varying density and water density changes with temperature.
The Chemistry and Craft
200: Why Depth Matters
The 100 section gave you everything you need to brew a great cup. The guidelines work. Most days, most coffees, most kitchens, you're set.
Some of us want to know why.
Why is 200 degrees the right temperature? What's actually happening when the bloom rises? Why does the same coffee taste different on day three than on day fifteen? The chemistry of brewing is genuinely interesting on its own terms, and once you start noticing the variables, the cup gets more interesting too.
200 is the layer for the reader who wants to understand the mechanics. None of it is required to enjoy great coffee. All of it makes great coffee even more rewarding.
201: Grinding Deeper
In 101, we said burr grinders win on consistency. That's true. Here's why it matters.
When you grind a bean, you don't get particles of uniform size. You get a distribution. With a good burr grinder, that distribution is tight; most particles cluster around your target size. With a blade grinder, the distribution is wide. You get some particles much smaller and much larger than the average, all at once.
Why that matters: extraction speed depends on particle surface area. Small particles extract fast. Large particles extract slow. When your distribution is wide, you're simultaneously over-extracting the fines (which adds bitterness) and under-extracting the boulders (which leaves sourness and thin mouthfeel) in the same brew. Even particle size means even extraction. Even extraction means the cup you taste is the cup you were trying to make.
Two practical notes once you start paying attention to grind quality:
Fines. Even good burr grinders produce some very small particles. They contribute disproportionately to bitterness. Sifting through a fine-mesh sieve can remove them, though most home brewers don't bother. Still, it’s worth knowing the term so you can taste for it.
Roast level shifts grind behavior. Darker roasts are more brittle and grind finer for the same setting. If you switch from a light to a dark roast on the same grinder, your usual setting will run finer than usual. Adjust one or two clicks coarser until you dial it back in.
Older coffee also grinds differently than fresh coffee. As the bean's internal structure changes with age, the same grinder setting produces a slightly different particle distribution. This is one big reason to dial in by taste rather than by setting number.
203: Brewing Variables (Extraction Theory)
103 introduced the three brewing concepts: drip, immersion, pressure. 203 is about the variables you can actually move inside any of those methods, and what each one does to the cup.
There are five main levers.
Brew ratio. The weight of coffee to the weight of water. Pour-over is typically 1:15 to 1:17 (one part coffee to fifteen to seventeen parts water). French press ratios are sometimes around 1:14 for a more concentrated cup. Stronger ratios produce heavier, more intense brews. Weaker ratios produce lighter, more delicate ones. There's no universally correct number. Start at 1:16 and experiment from there.
Grind size. Already covered in detail in 201. Finer means faster extraction.
Water temperature. Already covered in 102. Higher temperature within the 195 to 205 range means faster, more aggressive extraction.
Brew time. How long the water is in contact with the coffee. Pour-over typically targets 3 to 4 minutes total. French press 4 minutes. Espresso 25 to 30 seconds. Longer contact means more extraction except with espresso which increases extraction in less time by adding high pressure.
Agitation. How much the coffee bed is disturbed during brewing. More agitation (stirring, swirling, aggressive pours) means faster extraction. Less means slower.
All five interact. Change one and the cup shifts. The art of brewing is balancing them against each other.
The industry has a useful way to measure the result. A specialty coffee, properly brewed, will measure around 1.2 to 1.5% TDS in the cup (using a refractometer) and will have extracted 18 to 22% of the soluble material from the grounds. Inside that range is the ideal brew zone. Outside it, the cup gets either thin and sour (under-extracted) or bitter and dry (over-extracted).
Most home brewers don't measure with a refractometer, and they don't need to. The reason these numbers exist is that someone, somewhere, did the work to define what great looks like as a target. The actual instrument is still your taste. The numbers just give you a vocabulary for what you're tasting when something is off.
301: Origin and Terroir
Terroir is a word perhaps most familiar from the wine domain. It means the combination of place-specific factors, altitude, soil, climate, rainfall, sunlight, ecology, that shape how a plant grows and what its fruit tastes like. Coffee has terroir the same way wine does.
The country name on the bag is a starting point, not the story. Two farms in the same country, even the same region, can produce cups that taste different.
What actually matters:
Altitude. Higher elevation means cooler nights, slower cherry maturation, denser beans. This tends to concentrate flavor compounds, adding depth and complexity. The majority of premium specialty coffee comes from farms at 1,000 meters (3280’) and above.
Soil composition. Volcanic soils (common in Central America, Ethiopia, Indonesia, & Hawai’i) tend to produce brighter, more nuanced cups. Clay-heavy soils tend toward fuller, chocolatier profiles. The mineral content the plant draws up from the soil ends up in the cup, in a very real way.
Climate and microclimate. Consistent rainfall, well-defined dry seasons, and moderate temperatures produce healthier trees and better-defined cherry ripening. Even within a single farm, individual plots often perform differently because of shade patterns, wind exposure, or slope.
Latitude. Coffee grows in a band roughly 25 degrees north to 25 degrees south of the equator, known as the "coffee belt." Everything else you taste in the cup exists inside those geographical limits. We do note, however, that there are some notable exceptions to this with some of the newer farming that’s occurring in California. We’ve not yet experimented with these coffees as overall yield is still relatively small.
When we describe a coffee as "Ethiopian" or "Colombian," we're describing a region large enough to contain enormous variation. When we describe a coffee as "from Fazenda Ambiental Fortaleza in São Paulo" or "from the Kaʻu region on the Big Island of Hawaii," we're naming something specific enough that the terroir becomes a real predictor of what you'll taste.
303: Varietals
There are over 120 distinct species of coffee in the world. Nearly all of them don’t produce large enough seeds and/or palatable flavors to turn into roasted coffee. These species do serve a purpose in the broader coffee world, contributing to research on new subvarietals and disease resistance. Almost all coffee traded in the world falls into only two species: Arabica and Robusta. There are some consumer versions of two other species called Excelsa and Highland Coffee but these represent around only 2% of commercial production.
Arabica accounts for about 60% of global coffee production, and nearly all of specialty coffee. It grows best at higher altitudes (1,000 meters and up), matures slowly, and produces cups with more nuance, sweetness, and clarity. Arabica is what specialty roasters like us work with almost exclusively.
Robusta accounts for the other 40%. It grows at lower altitudes, is more resistant to disease and heat, and yields more per plant. Robusta cups are more bitter, higher in caffeine, and less complex. Most commercial coffee, instant coffee, and some traditional Italian espresso blends contain Robusta. Rare specialty-grade Robusta exists, but it represents a tiny fraction of the market.
Within Arabica, hundreds of varietals exist, and the differences between them can be as significant as the differences between wine grapes. Rather than list them all, it's more useful to know how they group by region:
Ethiopia. The genetic homeland of coffee. Ethiopia has thousands of heirloom varietals, most unnamed and unclassified, often grouped simply as "Ethiopian heirloom" or by region (Yirgacheffe, Sidamo, Guji). These produce the floral, tea-like, wildly aromatic cups Ethiopia is famous for.
Central America and Colombia. Bourbon and Typica descendants dominate, along with modern hybrids like Caturra, Catuai, and Castillo. Gesha (originally Ethiopian, transplanted to Panama) is the region's most famous specialty varietal. Colombia has emerged as the current epicenter of experimental varietals like our Pink Bourbon.
Brazil. The world's largest producer. Bourbon, Mundo Novo, and Catuai are the workhorses. Heritage varietals like Java are finding a specialty home here through producers like FAF.
East Africa (Kenya, Rwanda, Burundi). SL28 and SL34, Kenyan-developed varietals, produce some of the most complex, blackcurrant-inflected cups in specialty. Rwanda and Burundi grow largely Bourbon.
Indonesia (Sumatra, Java, Sulawesi). Typica-derived varietals dominate, often processed with the region's signature "wet-hulled" method that produces heavy, earthy, low-acid cups.
If you find you love the flavor of a specific varietal (Gesha, Java, Pacamara, or others), you can chase that varietal across origins and processes.
104: Coffee Storage
How you store your coffee shapes how long it stays at its best. Our bags are non-reactive, opaque, sealed, and feature a one-way CO2 valve, so they handle the basics for you. Stored in the bag at room temperature, your coffee will hold its character for ten to fourteen days with minimal loss. For longer storage, an airtight container with a vacuum seal extends that window.
Freezer storage isn't necessary, but it's not off-limits either. If you do freeze, use a fully airtight container. Coffee is porous and will pick up flavors from anything else in the freezer.
The four things that age coffee are worth knowing by name:
Air. Oxidation is the slow fade of the volatile compounds that define specialty cup quality.
Heat. Rapid temperature swings accelerate aging.
Light, especially direct sunlight.
Moisture.
An opaque container in a cool, dry, dark place handles all four without needing anything fancy.
We’re working on recommended storage solutions for our Hardware section so keep an eye on this or reach out if you want specifics in the meantime.
202: Water Chemistry
Water is a chemistry problem, and it's more nuanced than a single number. The 100 section said quality matters. Here's what's actually going on.
Two related but different metrics come up when people talk about brewing water: TDS and hardness.
TDS (total dissolved solids) measures everything dissolved in the water, in parts per million. Minerals, salts, organic compounds, all of it. TDS tells you how much is in your water. It doesn't tell you what kind.
Hardness specifically measures calcium and magnesium, typically reported as parts per million of calcium carbonate equivalent (CaCO3). Hardness is what scales up your equipment over time, and what most water filter manufacturers target.
This distinction matters because two waters with the same TDS can taste completely different depending on the mineral ratio. A water that's 150 ppm TDS dominated by calcium will brew a heavier, fuller cup than a water that's 150 ppm dominated by magnesium and bicarbonate. The Specialty Coffee Association's 150 ppm TDS guideline assumes a particular balance. Real water rarely matches it, so the number is a starting reference rather than a firm rule.
The minerals that actually shape the cup:
Calcium pulls out body and texture. More calcium, heavier mouthfeel.
Magnesium pulls out brightness and acidity. More magnesium, more sparkle in the cup.
Bicarbonate buffers acidity. Too much and the cup goes flat. Too little and acidity dominates.
The trade-off most home brewers run into:
Equipment loves soft water. Espresso machines especially can't tolerate hardness much beyond about 50 ppm CaCO3 over time without scaling up and eventually failing. If you brew espresso at home, an in-line hardness filter is essentially required, and you'll need to change it on a schedule based on your incoming water's hardness.
Flavor wants some mineral content. Pure water (zero TDS, zero hardness) struggles to extract well; the cup ends up flat and one-dimensional. Some minerals are what give the cup its body and brightness.
These two needs aren't opposed if you handle it right. A practical setup: filter your line down to a hardness level your espresso machine can live with (we filter to keep hardness under 50 ppm CaCO3 here at Duality, swapping the cartridge once it reaches that threshold), and use that same filtered water for all your other brew methods too. You give up a little flavor potential at the high end (a mineral-tuned brewing water might cup slightly differently), but the cup is still excellent and your equipment lasts.
Two paths beyond this if you want to dial in flavor further:
Commercial brewing water products. Pre-dosed sachets or bottled brewing water target specific mineral profiles in distilled water. This gives you a consistent and reliable starting point but also adds cost & can be cumbersome.
DIY brewing water. Home recipes (a few floating around coffee forums) let you mix your own from distilled water and a few household salts. Cheaper long-term, hands-on.
A note on Colorado specifically: tap water here runs hard. Significantly higher than the SCA's 150 ppm TDS reference, and well beyond what an espresso machine can tolerate over time. If you've ever wondered why your home cup tastes different from the same coffee brewed at a specialty cafe, water is probably half the answer.
204: The Freshness Window
104 covered the four things that age coffee. 204 is about what's actually happening when coffee is at its best, and how to find the freshness window for your batch.
Coffee has a stretch of time after roasting when it's at its peak. Roasters and writers love to chart it ("drink between day 7 and day 21," or similar), but those charts are looser than they admit. A light Ethiopian natural lives on a different timeline than a dark Sumatran. Filter behaves differently than espresso. The grinder matters. The water matters. Your morning matters.
The honest version: there are two loose bookends, and between them the window is wider than any single chart can tell you.
The front edge: outgassing.
Fresh-roasted coffee is outgassing carbon dioxide. For the first few days off-roast, there's enough CO2 still coming out of the bean from the roasting process that brewing can be inconsistent and unpredictable. The bloom is dramatic, extraction is uneven, the cup can taste flat or weirdly sharp. This is the period some of us experience as "fresh coffee that somehow falls short of great." It's worth resting through.
The back edge: staleness.
The volatile compounds that make specialty coffee taste like fruit, flowers, chocolate, and everything else specialty drinkers care about fade slowly over days and weeks. Eventually the cup feels hollow. Not undrinkable. Just thin. That's a stale coffee.
Between those two edges, past the outgassing and before the fade, is the window.
Inside that stretch, no chart can tell you where your peak is. The peak of any bag is the cup in front of the person drinking it. Try the same coffee at day five, day twelve, day twenty-five. You'll have a preference. That preference is more accurate than anything we could write down for you, because your palate has more information about your coffee setup, your brew method, and your morning than any guide ever will.
This is why roast-to-order matters in a way that's different from how it usually sounds. The grocery-store model is structurally indifferent to where on the curve you open the bag. Roast-to-order isn't a promise of a perfect cup. It's a promise of something more useful: the start of the window arrives in your hands. From there, the choice is yours. We’ve even made a printable chart for you to track your tasting by day as a helpful tool. Check it out HERE.
300: Why the Bean Before the Cup Matters
Section 100 covers the basics to prepare and brew consistent and tasty coffee. Section 200 covers chemistry and deeper understanding of the what, how and the why. 300 is about everything that happens before the coffee bean/seed reaches you.
Origin. Farm. Varietal. Processing. Roast profile. How the coffee moved from a tree to an airtight container to your kitchen. All of it shapes what's in your cup, sometimes more than anything you do at the grinder or brewer.
This is the layer for readers who want to think about coffee the way the industry does. Terroir, processing, sourcing, grading. Some of it becomes practical for how you shop for coffee. Some of it stays purely fascinating. Both are worth the time.
What follows below may not change your brew technique or daily practice… It may change your perspective of the coffee that you make, however.
302: Processing Methods
Once a coffee cherry is picked, what happens next shapes the final cup more than many people realize. Processing is the set of steps that turns fresh cherries into green coffee ready to be roasted, and the choices made at this stage produce dramatically different flavors from the same varietal grown on the same farm. Many roasters note the processing method right on the bag, sometimes in the big print. What does it all mean though?
Five main processes matter:
Washed (also called "wet-processed"). The cherry flesh is stripped off, and the beans are fermented in water tanks to remove any remaining mucilage before drying. Washed processing produces the cleanest, most transparent cups, with the varietal and terroir characteristics coming through clearly. This is the most common, modern processing method for both mass and specialty coffee.
Natural (also called "dry-processed"). The cherries are dried whole, with the flesh still attached to the bean. The bean absorbs sugars and flavors from the fruit as it dries. Natural processing produces sweeter, fruitier, more intense cups. It's the oldest processing method (Ethiopia has been doing it for centuries), and it's been enjoying a specialty renaissance for the last decade. It also takes more time & space to complete so that’s why you may see a price difference between a washed and natural processed coffee from the same farm.
Honey processing. A middle path between washed and natural; some or most of the cherry flesh is removed, but the sticky mucilage layer stays on during drying. Honey processing produces cups with body and sweetness in between the two extremes. It’s named for the sticky "honey" coating, not for any honey flavor or actual honey added to the process.
Anaerobic fermentation. A newer specialty technique where cherries or beans are sealed in oxygen-free tanks for a controlled period before drying. The fermentation environment produces distinctive, sometimes intense flavors: tropical fruit, wine, spice, floral notes. Anaerobic fermentation is behind many of the most talked-about specialty lots of the last few years. Our Brazil Java from FAF is a 36-hour anaerobic natural, which is where those jasmine and light chocolate notes come from.
Co-fermentation. The frontier of specialty processing right now. Producers introduce other fruits (mango, passion fruit, strawberry), spices, or specific yeasts into the fermentation vessel alongside the coffee cherries. The result is cups with intense, sometimes unexpected flavors that echo the added ingredient without literally tasting like it. Co-fermentation genuinely divides the specialty world. Some purists argue the added flavors aren't authentically from the coffee. Producers and roasters chasing new expressions are pushing the technique forward regardless.
The takeaway: "washed," "natural," "anaerobic," "co-ferment" on a bag isn't decoration... it's a predictor of what the cup will taste like, sometimes more than the country of origin.
304: Roast Profiles
Roasting is where green coffee (which tastes grassy and sour if you were to brew it) becomes the aromatic, complex beverage we recognize. The decisions each roaster makes during the process carry significant impact on the final cup. Roasting is part science, part art. It’s the final step in the whole production process before you get to enjoy your coffee!
The three broad categories most people know are based on the final color of the roasted bean/seed which you can specifically measure. We also measure it with the amount of mass loss during the roasting process. The darker the roast, the more mass loss from green.
Light roast. Shortens the final development phase of the roast to preserve the maximum of the bean's origin character: acidity, floral notes, fruit, complexity. The cup tastes most like where the coffee came from. Best suited to pour-over and other manual brewing methods but becoming more common with espresso enthusiasts.
Medium roast. Beans/seeds remain in the development phase of the roast primarily to balance origin character with the caramelized sugars that come from further roasting. More body, more chocolate and nut notes, less acidity. Works across most brew methods.
Dark roast. Development continues into or past second crack. The roasting process itself becomes the dominant flavor: caramelization, char, roast character. Origin character fades. Body increases. Since we don’t blend and offer only origin roasts, our approach to dark roast coffee differs from what you will find elsewhere in the market. Our dark roast profiles, like all our coffee, are meant to accentuate the nature of the origin, not homogenize it.
The light/medium/dark labels are helpful but blunt. Which roast level is right for a given coffee depends on the specific bean, its origin character, and what the roaster is trying to bring out.
305: How Specialty Coffee Is Graded, Traded, and Valued
The last piece of the 300 story is the supply chain: How coffee moves from farm to roastery, how quality gets certified along the way, and how prices actually get set. This is where terms like "specialty," "fair trade," "direct trade," and "Q grade" live.
Specialty coffee. A technical grade set by the Specialty Coffee Association (SCA). Coffee is cupped and scored by certified professionals; anything scoring 80 or higher out of 100 qualifies as specialty. Below 80 is commercial-grade coffee. All Duality coffees are specialty grade.
Q grades. The specific numerical score assigned during cupping. 80 to 84 is specialty. 85 to 87 is exceptional. 88 and above is rare microlot territory. 90+ is very rare and often auction-priced. The system is useful for green buyers making sourcing decisions. Less useful for consumers deciding what to drink. We have a separate note on why we don't put Q grades on our product pages, elsewhere on the site.
Fair trade. A certification scheme designed to guarantee farmers a minimum price and better working conditions. Well-intentioned. In practice, fair-trade certification often locks farmers into commercial-grade production because the certification premium is small and the specialty market pays much more. Most specialty roasters don't rely on fair-trade certification, but that doesn't mean they don't care about sourcing ethics.
Direct trade. Not a certification. A relationship. The roastery buys directly from a specific farm or cooperative, sometimes with multi-year agreements, negotiated prices well above commodity or fair-trade rates, and personal knowledge of the farm's practices. Direct trade produces the highest-quality coffees and the most sustainable economics for producers, but it requires roasters to do the work of building and maintaining producer relationships.
Traceability. How specifically the coffee's origin can be identified. A commercial coffee might be labeled "Brazil, blend of many farms." A specialty coffee is typically traceable to a specific region and often a specific farm. A direct-trade lot is traceable to the specific lot, harvest, and processing batch.
At Duality, we’re focused on developing direct-trade partners around the world. This is the best way to guarantee that we get both the highest quality product while supporting sustainable and innovative farms/producers. Our commitment to specialty grade is table stakes. The direct-trade choice is where the actual sourcing ethics live. We’re thrilled about the direction and evolution of coffee and love to be a part of pushing that bright future.