Guides

What the coffee-to-water ratio is, why it varies by brewing method, and how to use it to control strength.

How grind size affects extraction, and which grind range suits which brewing method.

What studies found when brewing temperature was varied, why the kettle and the brewer differ, and how cold brewing changes the drink.

Strength and extraction as two different things, what studies found about sour and bitter, unevenness, and what a filter holds back.

How steaming milk works, and why texture differs between drinks like cappuccino, latte and flat white.

How to keep each kind of coffee, what a freezer trial and the packaging studies measured, and where the usual advice is custom.

A starting point for diagnosing the most frequent brewing complaints, linking to detailed troubleshooting pages.

Why regular cleaning and descaling matters across every brewing method and machine, what maintenance symptoms actually mean, and when to stop and call a professional.

What actually happens to a coffee bean during roasting, from drying through first and second crack.

Why caffeine content varies so much between drinks, and how decaffeination actually works.

How country, region, producer, farm, lot, species, variety, process and roast relate to each other — and why none of them alone predicts flavour.

Instant coffee is brewed coffee with the water taken out: how the extract is made and dried, what the law lets it contain, and why humidity is what spoils it.

How caffeine is taken out of green coffee, what regulators say about the solvents, and how much caffeine a decaf still contains.

Bottled/canned coffee, cold-brew concentrate and coffee concentrate, explained — and how they differ from home-brewed cold coffee.

Chicory, roasted grain and other traditional coffee substitutes — what they are, whether they contain caffeine, and why people use them.

Mushroom coffee, butter coffee, collagen coffee and other trend products — what's marketing, and what has genuine (if often preliminary) evidence.

Aroma, acidity, body, balance and finish, explained in plain language — plus how professional cupping works and how to run a useful tasting at home.

How to tell a measured impact from a modelled footprint, a certified rule, a legal duty and a seller's own claim, with what one study of coffee's footprint found.

What the husk, pulp, mucilage, parchment, silverskin and spent grounds are, where each arises, and which uses for them are established or only proposed.

What cascara actually is, how it's brewed, its caffeine content, and how it differs from the unrelated herbal product "cascara sagrada."

There is no world grade for green coffee. What several national systems count, what a defect and a screen number are, and how far a physical grade predicts the cup.

Grams versus ounces, Celsius versus Fahrenheit, bar versus psi, and why a US cup, an imperial cup and a café serving size aren't the same volume.

How a coffee's price is made: the exchange contracts, the differential for a particular coffee, sales with the price fixed later, and what dated studies found reaches the farm.

What Fairtrade, Rainforest Alliance, organic, Bird Friendly and 4C each require, read from their own standards where those were opened, and what a certificate does not show.

What can go wrong between a real origin/variety/lot and what's printed on the bag — and what buyers can and can't verify themselves.

What dosing, distributing and tamping an espresso puck are for, which parts rest on a study and which on practice, and what none of it can fix.

Three-way valves, boilers, steam wands and baskets — the four machine characteristics that decide which espresso advice applies to you.

The trade's standard comparison protocol, why every part of it exists, and which parts a home taster can drop.

The six World Coffee Championships and the Cup of Excellence, from their 2026 rules: the format of each, what is judged, and what a result does not tell you.

What green coffee is, the steps between dried parchment and a shipped lot, what an assessment measures, how samples are used, and what lot and crop terms do and do not mean.

How green coffee gains and loses water in a warehouse and in a shipping container, what sacks and sealed liners do, and what studies of packaging found.

Who owns a coffee at each step between the farm and the roaster, what a contract fixes, what free on board means in the coffee trade, and where the risk sits.

How a coffee bar's day is usually organised, what each decision depends on, what food-safety rules require of milk, and what a machine's maker decides.

Why grinder choice matters more than most other equipment decisions, and what to look for.

What roast date, origin, process, roast level and certification labels actually tell you — and what they don't.

Espresso and milk terminology, drink sizes and ordering language vary by country — a practical guide to what to expect, without claiming one global standard.

What to buy, in what order, and what to leave until you have a problem it would solve.

How to set up and use a Sage or Breville Barista Express, Pro, Express Impress, Touch or Touch Impress: what every control does, baskets and buttons, grinding, the gauge, milk and cleaning.

How to set up and use a Sage or Breville Bambino or Bambino Plus: pairing it with a grinder, which baskets you have, the shot buttons, milk, cleaning, and how the two differ.

How to set up and use a Sage or Breville Oracle, Oracle Touch, Oracle Jet or Oracle Dual Boiler: what the automation controls, what it leaves to you, grind, milk and cleaning.

Hardness and alkalinity are different properties of water: what a controlled tasting found each does to coffee, and what each does to equipment.

A deeper look at what 'extraction' physically means, beyond the practical sour/bitter heuristic.

Why milk foams and steams the way it does, at a level beneath the practical steaming technique.

What was measured as roasted coffee ages: gas leaving over weeks, aroma compounds escaping or reacting, and what grinding and packaging change.

Drying, browning, first crack and development — the chemistry behind roast character, at the depth that changes what a roaster does.

How heat reaches the bean by contact, moving air and radiation, how drum and air roasters differ, and what the amount of air has been shown to do.

What a roast curve records, what rate of rise measures, why curves do not transfer between machines, and how much of the advice about their shape has been tested.

Baked, scorched and underdeveloped: what one laboratory found when it made roast faults on purpose, and why the names are looser than they sound.

What ferments when coffee is processed, which microbes do it, and what published trials found when they changed the time or chose the yeast.

How coffee is dried after processing: three phases, the moisture and water activity limits in international guidance, surfaces, turning and rewetting.

Anaerobic, carbonic maceration, thermal shock, co-fermented and infused: what each word is taken to mean, and how little has been published about most of them.

What a coffee refractometer reads, how extraction yield is calculated from it, where the errors come from, and why no reading guarantees a good cup.

How pressure and flow relate in an espresso puck, what one study found when flow was varied, and which familiar rules are convention more than finding.

What a green coffee seed contains, what roasting breaks down and builds, what dissolves into the cup, and why knowing the compounds does not yet explain the taste.

How a coffee tree roots, what sets off its flowering, how it is pollinated and the stages a cherry passes through between blossom and harvest.

The temperature, rainfall and dry season arabica and robusta are reported to need, what frost and wind do, and why altitude matters without higher being better.

What shade trees are reported to do for coffee and what they cost in yield, why planting density has no single answer, and where irrigation changes the crop.

Why cherries on one branch ripen at different times, the four ways coffee is picked, and what slope and the cost of labour decide.

Leaf rust, coffee berry disease, the berry borer, wilt and nematodes: what each organism is, what it does to the tree, where it occurs and how it is managed in principle.

What models project for the land that suits arabica, what has been observed, what is proposed in response, and what is not known.

Where arabica came from, why it has so little genetic diversity, what the Timor Hybrid added, why arabica and robusta are bred in opposite ways, and what F1 hybrids, pyramiding and genomic selection have been shown to do.

What an unroasted coffee seed contains and how much: cell-wall polysaccharides, sucrose, oil and its diterpenes, protein, chlorogenic acids and caffeine, what calling something a flavour precursor claims, and what changes in storage.

What soil does for a coffee tree and what coffee does to its soil: acidity under long monoculture, one field trial of nitrogen, phosphorus and the two species, root fungi, nitrogen-fixing shade trees, and what is and is not known about soil and flavour.

The espresso bed as a porous medium: permeability, why flow stops rising with pressure, wetting and swelling, fines, why extraction falls at very fine grinds, five meanings of channelling, and how little evidence stands behind tamping force.

What roasting does to each part of a coffee seed: water, sucrose, cell-wall polysaccharides, chlorogenic acids, trigonelline, caffeine and oil; where the carbon dioxide comes from; and what Maillard, Strecker, caramelisation and pyrolysis each claim.

The classes of volatile compound in roasted coffee (furans, pyrazines, aldehydes, ketones, sulphur compounds, phenols, pyridines, esters), how the ones that smell are identified, and the steps between a molecule in the cup and a word in a tasting note: thresholds, mixtures, the liquid and the taster.

Nine controlled comparisons a reader can run with a scale, a timer and a thermometer: water alkalinity, filter material, sieved fines, espresso flow, tamping force, needle distribution, resting, frozen beans and milk temperature, each with its controls, what to record and what the result cannot show.

Sorting the equipment that changes how coffee tastes from the equipment that changes how much mess you make — and being honest about which is which.

Caffeine, milk drinks and shared café equipment — the places a coffee drinker genuinely meets matcha, and where CoffeeHQ stops.