Roast Card
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 the Roast Card is
A Roast Card is a compact record of how a coffee was roasted, designed to be 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. The transition between phases is marked on the timeline beneath the curve, so it is visible 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 both 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 of the roast 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.
The first is the Product Page Roast Card. This is the reference roast — the target approach Glass uses when roasting that coffee. It answers the question of how a given coffee is roasted, and it sits on the product page as a stable reference alongside the origin data. The title format itself reflects that purpose: coffee name, roast type, and the date the reference profile was set — so the card reads as an established target, not a one-off record.
The card carries the target roast duration, the target internal bean end temperature, the turning point, first crack (timestamp and temperature) marked on the curve, and the three phases — drying, yellowing, and development — each shown with its own duration and percentage. Where the data supports it, the card also shows roast colour as two separate readings: ground and bean, on the medium-to-ultra-light scale.
Product Page - Roast Profiles
What the product page card deliberately leaves out is batch-level operational data: batch ID, roast date, roast time of day, operator. Including those on the product page would turn it into a roast log. The product page is about intent.
Email - Batch Trace
The second is the Email Roast Card. This one 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 that the product page card 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 suggest a measurement that was not necessarily taken for that specific batch.
The distinction between the two is deliberate. The product page says: this is how we roast this coffee. The email says: this is how your coffee was actually roasted. One sets the expectation. The other delivers against it. The naming of the operator on the email card is part of that delivery — a roast arrives with a person attached to it, not only a number.
Why we are doing this
A customer should be able to understand what they are consuming. 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. Source transparency is now reasonably common in specialty 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 transparency loop that is open at one end: a customer can learn where their coffee came from but not what was done to it between the green and the bag.
Specialty coffee is also a comparatively small world at the green stage. The same handful of producers, farms, and varietals appear on bag after bag across the industry, and Glass shares some of them with peer roasters we admire. What gives a roaster their character, in many cases, is the roast itself — and that is precisely the part that usually stays inside the roastery. Without it, 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. The Roast Card is one way of making the part of the difference that lives in the roastery visible at the point of sale.
For most customers, that visibility is a meaningful influence on cup outcome. The same green, roasted two different ways, will taste like two different coffees. Leaving that decision invisible is a quiet gap in the story.
The reason that precision is worth publishing in the first place is that, in our roastery, small numbers can carry meaningful differences. 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. Neither is necessarily wrong, and 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. But for most coffees, there is a small target where the cup tends to land best. We roast within tight tolerances — typically within a degree of release temperature — to keep our roasts on that target, and the Roast Card publishes both the target we aim for and the actual roast that was achieved, so the distance between the two is visible to anyone looking.
The Roast Card is our answer to the gap in the story. It does not dramatise roasting; it documents it. It applies the standard we already apply to origin data — specificity over suggestion, evidence over claim — to a step that lives at the intersection of craft and measurement.
How it connects to the rest of the page
On the product page, the Roast Card sits between the origin section above and the tasting notes, 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 that sits in the middle: what we did to the coffee in the roastery.
In time, the Roast Card will be joined by a Flavour Map — a complementary section we are working on, which will translate the technical roast target into sensory language. The two together 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 reveals
At the level of 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 do not 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 recognition is part of the point. It 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.
That is the level of transparency we intend to build toward across the menu - milk, tea, salt, and every other ingredient we serve. The Roast Card is where it starts for coffee.