Barista foundations

What you will be able to do

• Weigh a dose and a brew and state the ratio between them
• Explain the difference between a strong cup and a well-extracted one
• Predict which direction a grind change will move the taste
• Tell from a roast date whether a coffee is too fresh, in its window, or fading
• Set up a station where a mistake is visible rather than hidden

Assumes: nothing. This is where the programme starts.

Why a barista weighs everything

CoffeeHQ explanation of the mechanism

Coffee is made from two ingredients, and the first professional habit is knowing how much of each went in. A scoop of dark roast weighs less than the same scoop of light roast, because dark beans are larger and less dense. A 'cup' of water is whatever the cup holds. Volume hides both variations; a scale removes them.

The dry coffee is the dose. The water you pour is the brew water. In espresso the liquid in the cup is weighed instead and called the yield, because some water always stays behind in the grounds. Timing is the third measurement: it does not tell you whether a coffee is good, but it tells you whether today's brew behaved like yesterday's.

None of this is about precision for its own sake. It is about being able to change one thing on purpose. Without a scale and a timer, two brews differ in ways you cannot name, and there is nothing to learn from comparing them.

In more depth: Digital scale · Coffee units and measurements

Ratio sets strength

Common convention — cafés and regions differ

The brew ratio is the weight of water for each gram of coffee, written 1:16 for sixteen grams of water per gram of coffee. A smaller second number means more coffee for the same water, and a stronger drink. Filter coffee is commonly brewed somewhere between about 1:15 and 1:17. Espresso is in a different range entirely, around 1:2, which is why it is so much more concentrated.

These are starting conventions. A ratio is not correct or incorrect; it is a decision about how concentrated you want the drink to be, and that depends on the coffee and on you.

In more depth: Coffee-to-water ratio · Ratio and strength calculator

Extraction sets flavour balance

CoffeeHQ explanation of the mechanism

Roughly a third of a roasted coffee bean can dissolve in water, and a good brew takes only part of that. Extraction is how much of each particle ended up in the cup. It is a separate question from strength: a cup can be strong and under-extracted, like a short espresso pulled too fast, or weak and over-extracted, like a little coffee steeped for far too long.

What dissolves changes as a brew goes on. Sharp, acidic compounds come out early, sweetness and body build through the middle, and bitter, drying compounds arrive late. That order is why an under-extracted cup is usually described as sour and thin and an over-extracted one as bitter and drying.

Almost all confused brewing advice comes from mixing these two ideas up. 'Brew it longer to make it stronger' changes extraction, not strength. Keep them apart and most problems become one question: is this cup the wrong strength, or the wrong balance?

In more depth: Extraction basics · Extraction science

Grind is the main control over extraction

CoffeeHQ explanation of the mechanism

Finer grounds have more surface for the same weight, so water dissolves more from them in the same time. In a brewer where water flows through the coffee, finer grounds also slow the flow, which lengthens contact. Both effects push the same way, so grind is the most powerful single adjustment you have.

Each method has a workable range, set by how long its water stays in contact with the coffee: fine for espresso's half-minute, medium for a few minutes of pour-over, coarse for a long steep. A burr grinder matters because it produces particles of similar size. A blade grinder produces dust and boulders together, which extract at different rates in the same brew.

In more depth: Grind size · Adjusting grind size

Freshness, water and a clean station

A typical tendency, not a guarantee

Roasted coffee releases carbon dioxide for days after roasting and loses aroma for weeks. Very fresh coffee can brew unevenly and unpredictably, particularly as espresso; old coffee tastes flat and offers little resistance to water. Many roasters suggest resting coffee for several days to a couple of weeks before espresso, and the best window depends on the roast. Look for a roast date, not a best-before date.

Brewed coffee is almost entirely water, so water that tastes of chlorine or is very hard will show in the cup. And coffee oils left on a basket, a shower screen or a jug turn rancid and flavour the next drink. A barista's station is clean for a practical reason: old coffee is an ingredient nobody chose.

In more depth: Bean freshness · Resting roasted coffee · Water chemistry and brewing

Practise with a tool

Exercise: The ratio ladder

See all practical exercises

Work it through: The second cup is always worse

Someone makes two mugs of filter coffee each morning using a scoop and the lines on the kettle. The first mug is usually fine. The second is often weak and sharp. Same coffee, same brewer.

Reasoning it out

1. Nothing is being measured, so the two brews could differ in dose, water or both.
2. A scoop varies by a gram or two each time, and more when the bag is nearly empty and the beans are broken.
3. The second brew is made in a hurry: less water in the kettle, cooler by the time it is poured, poured faster.
4. Weak and sharp together points at less coffee or less extraction, or both.

What to do

Weigh both doses and both pours for a week before changing anything else. If the second mug improves, the problem was never the coffee or the brewer; it was that the two brews were different recipes.

Coffee too weak

Check yourself

Answer in your head first. Nothing is scored and nothing you open here is recorded.

1. 1. You brew 15 g of coffee with 255 g of water. What is the ratio, and is it stronger or weaker than 1:16?

   Show the answer

   1:17, which is weaker than 1:16.

   255 ÷ 15 = 17. A larger second number means more water per gram of coffee, so a less concentrated drink.

   Back to “Ratio sets strength”

2. 2. A cup tastes thin and sour. Which is the better first move?

   • Add more coffee
   • Grind finer
   • Use cooler water
   Show the answer

   Grind finer.

   Sour and thin together suggests under-extraction. More coffee would make the cup stronger and still sour; a finer grind extracts more from each particle.

   Back to “Extraction sets flavour balance”

3. 3. Why does a scoop of dark roast weigh less than a scoop of light roast?

   Show the answer

   Dark-roasted beans are larger and less dense.

   Beans expand and lose mass as they roast, so the same volume holds less coffee by weight. Weighing removes the difference.

   Back to “Why a barista weighs everything”

4. 4. True or false: brewing for longer is a reliable way to make coffee stronger.

   Show the answer

   False.

   A longer brew extracts each particle further, changing the balance towards bitterness. Strength is set by the ratio.

   Back to “Extraction sets flavour balance”

Comparisons worth making now

• Kitchen scale or espresso scaleAny scale beats none; this explains when resolution and response time start to matter.
• Hand grinder or electricThe grinder decides how evenly your coffee extracts, more than the brewer does.

Reference for this level

• Water temperature
• Why coffee goes stale
• Choosing a grinder
• Grind-size guide
• Brewing variable explorer

Where the facts in this level come from

• SCA brewing and espresso standards — Specialty Coffee Association (SCA)
• UC Davis Coffee Center research — University of California, Davis — Coffee Center

Sections are labelled with the kind of claim they make. How CoffeeHQ uses sources, and what each one is relied on for, is set out in the source and evidence policy.