Not just where it came from. How it was roasted.
We have spent much of the past year making the origin side of our coffee easier to understand. The roast is the other half of the story. This is how we intend to make it visible.
Most of what is known about a bag of Glass coffee lives on the product page before you place an order. Variety, altitude, harvest dates, processing method, lot detail, the producer behind it. A customer who wants that information can see it without asking, and a customer who does not can still recognise a cleanly sourced coffee when they see one.
Product data does not end at origin, though. Between the green coffee arriving at the roastery and the bag leaving it, a number of decisions are made - target temperature, development time, the shape of the curve, the colour we aim for - and those decisions shape a large part of how the cup tastes. In most of the industry, that step is invisible to the customer. The Roast Card is how we intend to close that gap.
What's on the card
A Roast Card is a compact record of how a coffee was roasted: readable without specialist knowledge, with detail there for anyone who wants to go deeper.
At its centre is the roast curve. Four temperatures are plotted across the same axis — hot air, drum surface, bean surface, and internal bean — and the curve is divided into three colour-shaded phases: drying, yellowing, and development. Each phase transition is marked on the timeline beneath the curve, so you can see where one phase ends and the next begins.
Below the curve sit the values that define the roast: target roast duration and target end temperature; turning point and first crack, each with a timestamp and a temperature; and the duration and percentage of each of the three phases. Where the data supports it, the card also carries a roast colour reading — taken separately for the ground bean and the whole bean, on a scale from medium through light to ultra light.
Rather than reduce the roast to a single label — light, medium, dark — the card gives a specific, technical picture of how the coffee was taken through the roastery: how hot, how long, and where each phase occurred.
A reference Roast Card: hot air, drum surface, bean surface, and internal bean temperatures tracked across the drying, yellowing, and development phases, with the key events of the roast — turning point, first crack, target end — visible against the curve.
Two cards, two jobs
We have designed two versions of the Roast Card, because they answer different questions. One sets the expectation. The other delivers against it.
The product page card is the reference roast — the target approach Glass uses when roasting that coffee. It answers a single question: how is this coffee roasted? It sits on the product page as a stable reference alongside the origin data, and its title says so — coffee name, roast type, and the date the reference profile was set, so the card reads as an established target rather than a one-off record.
It carries the target roast duration, the target internal bean end temperature, the turning point, and first crack (timestamp and temperature) marked on the curve, along with the three phases — drying, yellowing, and development — each shown with its own duration and percentage. Where the data supports it, it also shows roast colour as two readings, ground and bean, on the medium-to-ultra-light scale.
What it deliberately leaves out is batch-level operational data: batch ID, roast date, roast time of day, operator. Including those would turn the product page into a roast log. The product page is about intent.
Product page: the reference roast
Email: the batch behind your bag
The email card ships with the order and shows the actual roast event used for that specific bag. It carries the same curve and phase visualisation as the product page card, populated with what actually happened: actual roast length, actual end temperature, actual turning point, actual first crack.
Alongside the curve, it carries the operational record the product page leaves out — batch ID, batch size, roast date, roast time of day, and the name of the operator who pulled that batch. It does not show roast colour: colour is held as a reference standard for a coffee rather than a per-batch reading, so it lives on the product page, where it can be set against the target, not on the email, where it would imply a measurement that was not necessarily taken for that batch.
The distinction is deliberate. The product page says: this is how we roast this coffee. The email says: this is how your coffee was actually roasted. Naming the operator is part of that delivery — a roast arrives with a person attached to it, not only a number.
Why the roast belongs on the page
A customer should be able to understand what they are consuming, and that understanding should not depend on insider knowledge, specialist language, or trust in brand voice. It should be available at the point of sale, in a form specific enough to be credible. We already hold origin data to that standard. The roast should be no different.
The transparency loop is open at one end. Source transparency is now reasonably common in speciality coffee — a number of companies will tell you the farm, the variety, and the altitude. Far fewer will tell you how the green was roasted. The result is a customer who can learn where their coffee came from but not what was done to it between the green and the bag.
Much of a roaster's character lives in the roast. Speciality coffee is a small world at the green stage. The same handful of producers, farms, and varietals appear on bag after bag across the industry, and we share some of them with peer roasters we admire. What distinguishes one roaster from another, in many cases, is the roast itself — and that is precisely the part that usually stays inside the roastery. Two coffees can share a producer, a varietal, and a process and still arrive in the cup as quite different things, with little visible explanation of why.
Small numbers carry the difference, which is why they are worth publishing. The same green coffee, roasted two ways, can taste like two different coffees. Across varieties, processes, and densities, we have come to observe narrow windows — sometimes as tight as fifteen seconds at the end of a roast — where the cup tends to land in a different place. A washed Geisha released at 7:35 and the same coffee released at 7:50 are not always the same coffee in the cup, even at a very similar end temperature. For most coffees there is a small target where the cup lands best, and we roast within tight tolerances — typically within a degree of release temperature — to stay on it. The card publishes both the target we aim for and the actual roast achieved, so the distance between the two is visible to anyone looking.
We are not always right, and we don't pretend to be. We are sometimes surprised by what falls outside the window we were aiming for; some of our best results have come from those surprises and gone on to shift the recipe. The card records that honestly rather than tidying it away.
What the card proves, and what it doesn't. The Roast Card shows roast intention and the result achieved against it. It does not claim to guarantee a flavour. It does not dramatise roasting; it documents it — applying the standard we already apply to origin data, specificity over suggestion and evidence over claim, to a step that sits at the intersection of craft and measurement.
Where it sits: the hinge between origin and cup
On the product page, the Roast Card sits between the origin section above and the tasting, resting, and brewing notes below. It is the hinge between the sourcing story and the cup. Above the card, the page covers where the coffee came from. Below it, the page covers what the coffee should taste like and how to make it. The Roast Card answers the question in the middle: what we did to the coffee in the roastery.
In time, it will be joined by a Flavour Map — a complementary section we are working on, which will translate the technical roast target into sensory language. Together they will form a fuller account of what Glass does with each coffee after it arrives. For now, the Roast Card is the part of that account that is live.
What it changes
At the level of the product, the Roast Card makes roast decisions available to anyone who wants to look at them. It gives customers who care about roast data a way to read it, and customers who don't a clean visual that still carries useful information — a curve, a phase shape, a development percentage, a colour reading. The email version extends that into the order itself, naming the batch and the person who pulled it.
Over time, the card becomes a reference of its own. The more Roast Cards a customer sees, the easier it becomes to recognise the shapes they prefer — the curves that produce the cups they like, the development phases that suit their taste, the roasters whose approach matches their own. That is how a customer moves from trusting a label to recognising a style.
At the level of the company, the Roast Card is a position on where transparency should go. Demanding traceability at source is important, but it is not the whole job. The roaster's decisions shape the cup as much as the producer's, and a company that asks customers to trust its sourcing standard has no good reason to leave its roasting standard unstated.