Green coffee study at the intermediate level stalls when topics stay separate: contracts in one mental drawer, defect grading in another, cupping in a third. The practical angle here is to keep a single running example lot — name an origin, a process, a moisture reading, a defect list, and a contract type — and push it through every topic you study. Price it under a differential, grade its defects, predict its cup, then check your predictions. One note on logistics: administrative details such as exam format and scheduling belong to the SCA and its authorized trainers, so confirm them there rather than in study summaries.
Fixed price versus differential contracts: which number actually moves
A fixed-price contract sets the whole green price when you agree. A differential contract fixes only the premium or discount over a market reference, so the final invoice price still depends on when the reference price is set.
A differential is the premium or discount a specific lot earns above a market reference, reflecting origin reputation, quality, certification, and logistics. When a contract reads 'C plus thirty cents,' only the thirty cents is settled at negotiation; the reference component is fixed later on the fixing date the contract defines. The learning difficulty is that both numbers sit inside one written term, so learners read the whole expression as a total price rather than a fixed part plus a floating part.
Worked scenario: a roastery agrees to buy a washed lot at 'C + 30' with the price fixed before shipment. Later the reference market rises from an illustrative 170 to 190 cents per pound. The plausible mistake is worrying that the deal changed because 'the price moved' — the differential is still 30. The better decision is to name which term is fixed and which floats, then compute the invoice at 220 cents per pound equivalent using the fixing price. Same contract, different invoice: that is the mechanism worth drilling.
| Contract term | What it fixes | What stays open | Learner error to avoid |
|---|---|---|---|
| Fixed price | The full green price, agreed up front | Almost nothing price-related | Recalculating the price after market moves |
| Differential (market reference plus premium or discount) | Only the premium or discount over the reference | The reference price until the fixing date | Reading 'C + 30' as a total price of 30 |
| Price to be fixed (open) | Nothing yet; both sides defer pricing | Both the reference level and the timing | Assuming the differential itself changes with the market |
Green grading arithmetic: full defects versus partial defects
Green grading separates defects by severity. Full defects, such as black or sour beans, count one each; partial defects, such as broken or insect-damaged beans, count in groups, so similar-looking samples can grade very differently.
The distinction exists because severity tracks risk differently. Categories you will meet in training include full black, partial black, full sour, partial sour, dried cherry, fungus damage, foreign matter, broken and chipped beans, hulls, and insect damage. Full-severity defects convert directly into defect equivalents; partial-severity defects convert at a fraction, commonly taught as several partials equal to one full equivalent. Your course materials carry the current sample weight and conversion values, and those values drive the grade a sample earns.
Worked exercise on a 350 g practice sample, using assumed SCA-style values purely for illustration: 6 full black beans, 10 broken beans, and 15 insect-damaged beans. The plausible mistake is counting every bean once and reporting 31 defects. The better decision is to split by severity: 6 full defects from the black beans, 10 broken beans at five-to-one giving 2 equivalents, and 15 insect-damaged beans giving 3, for 11 defect equivalents. The black beans also raise a cupping flag, while broken beans mainly threaten physical uniformity. Verify current conversion values against your course protocol before relying on any count.
Moisture content versus water activity: one safe number is not enough
Moisture content measures how much water the bean holds. Water activity measures how available that water is to mold and chemical reactions, so a lot can pass a moisture test and still be unstable in storage.
These two measures answer different questions, and intermediate green coffee work expects you to keep them separate. Moisture content, commonly taught with targets around 11 percent for green coffee, describes the bean itself and affects density, roasting behavior, and traded weight. Water activity describes the freedom of that water and predicts storage stability, mold risk, and aging behavior. Two lots at the same moisture percentage can carry different water activity readings, and only the water activity number tells you how the lot will behave over time in a warehouse.
Consider an exporter whose lot reads 11.0 percent moisture after weeks beside a humid warehouse wall. The plausible mistake is releasing the lot on the moisture figure alone, because that reading was taken at intake. The better decision is to re-check both measures before shipment, especially for lots that sit in storage or travel through humid climates. If water activity has crept upward while moisture barely moved, the lot needs drying or faster dispatch. The scenario matters because shelf time is where stable-looking lots quietly deteriorate.
Processing method changes what you see and how you classify a lot
Washed, natural, and honey processing leave different fingerprints on the green bean, so classification inputs such as appearance, defects, screen size, and density should be read with the process behind the lot in mind.
Naturals dry inside the whole fruit, so the green bean shows more color variation, more dried-cherry and sour-style defect risk, and a generally less uniform appearance than washed coffee, which dries as protected parchment. Honey processing sits between them. Screen size and density grading apply the same way across processes, but the distributions you expect differ: a natural that looks uneven is not automatically defective, while a washed lot showing the same variation deserves closer inspection. Interpreting appearance without process context produces wrong conclusions in both directions.
Apply this by sorting samples by process before you judge them. Take one washed and one natural sample with similar visual variation and write down, for each, whether the variation is typical for the process or a defect signal. Then cup both. This trains a decision that matters throughout the module: classification is not a fixed checklist applied blindly, because the same physical evidence earns different interpretations depending on what the lot went through after harvest.
Linking green evidence to cup predictions, then testing the link
Each green attribute predicts specific flavor risks: defect severity, processing style, and moisture each point toward particular cup outcomes. Grading and cupping work best when each checks the other rather than standing alone.
Black and sour defects carry the clearest flavor warnings, which is part of why they count as full defects. Dried cherry in naturals suggests fermented or winey notes that may or may not suit the buyer. Floaters hint at uneven density and inconsistent roasting. Broken beans roast unevenly even when they taste clean. An intermediate learner should be able to look at a graded sample, name the dominant cup risk before the table is poured, and then use the cupping table to confirm or challenge that call.
Practice the link as a prediction game on your running example lot. After grading, write one sentence: 'This lot should taste X, and its main risk is Y.' Cup the sample and compare. When the prediction fails, treat the failure as information: either your defect reading missed something, or your cupping calibration drifted. Repeated prediction-and-check cycles build exactly the two-way fluency between the green table and the cupping table that connects this module's topics.
A repeatable self-check exercise with a scoring rubric
Run one two-part exercise repeatedly: price a practice lot under a differential contract, then grade a practice sample and predict its cup. Score yourself on contract logic, defect arithmetic, and prediction quality.
Set up the exercise with three cards. Card one: a contract line, for example 'C + 25, fixed before shipment,' plus a hypothetical fixing price of 185 cents per pound. Card two: a sample description with a defect list mixing full and partial categories. Card three: a process and moisture profile. Work all three cards in a single sitting: compute the invoice price, convert the defects to equivalents, and write a one-line cup prediction naming its main risk. Then check every answer against your course materials and adjust the cards for the next run.
Score each run out of nine, three points per card. Contract card: three points if you state which number is fixed, which floats, and the correct invoice at the given fixing price. Defect card: three points for the correct full-versus-partial split and equivalent count. Cup card: three points if your prediction names the right dominant risk category. These are learning milestones, not pass predictions. Expected early observations: partial defects get counted as full defects, and the fixing step gets skipped in favor of recomputing the whole price.
An adaptable preparation sequence and concrete readiness checks
Study in five blocks — contracts, defect arithmetic, moisture and water activity, processing and classification, then integration — and finish when you can price, grade, and predict one running example lot from memory.
Give each block a few sessions. Block one, contracts: fix the vocabulary and compute invoices at several fixing prices. Block two, defect arithmetic: drill full-versus-partial conversions until the split is automatic. Block three, moisture and water activity: define both measures in your own words and write when each should trigger a decision. Block four, processing and classification: sort mixed samples by process before judging them. Block five, integration: run the three-card exercise from the previous section until two consecutive runs score eight or higher.
Check readiness with four concrete tests. One: compute invoice prices at two different fixing prices without notes. Two: grade two samples a week apart and get equivalent counts within a small margin of each other, which shows your counting is stable. Three: predict the dominant cup risk for three samples and land on the correct risk category across repeated runs. Four: explain fixed price versus differential to a colleague in plain language. For exam format, scheduling, and current protocol values, rely on the SCA's education pages and your authorized trainer rather than on summaries like this one.
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.