Learn about coffee - Roasting – Sandbox Coffee Roasters

STEP 4 OF 5 - ROASTING

Brown is the new green

A green coffee bean has no aroma, no color, and none of the flavor we associate with coffee. It smells faintly of cut grass and has the texture of a pebble. Roasting is the transformation — and every decision made in those 10 to 15 minutes is a trade-off between what to preserve and what to develop.

Growing

Harvest

Processing

Roasting

Brewing

THE SCIENCE

What happens inside the bean

As the bean heats up, a sequence of chemical reactions transforms everything about it — color, density, aroma, and flavor. Three of them matter most.

Maillard reaction

Amino acids and sugars react under heat, creating hundreds of new aroma and flavor compounds. Responsible for the rich, complex, roasted character we associate with coffee.

Caramelisation

Sugars break down and transform. This is where sweetness, body, and darker, more bitter notes develop — and where the balance between them tips depending on how long the roast runs.

CO₂ development

The bean releases carbon dioxide during and after roasting. Freshly roasted coffee needs to degas before brewing — too much CO₂ interferes with extraction. It's why rest time after roasting matters.

ROAST LEVEL

The spectrum from light to dark

Roast level describes how far the transformation is taken — how long the bean stays in the drum, and how much heat it absorbs. It is the most visible variable in roasting, and the one most people are familiar with. But it is only half the story.

Light

~196–205°C

The bean's origin character is front and centre. Floral, fruity, and tea-like notes are preserved. Higher acidity, lighter body. The roaster's job is to get out of the way and let the green bean speak.

Balanced
Sweet
Versatile

Medium

~210–220°C

Balance between origin character and roast development. Sweetness comes forward, acidity softens, body increases. The most approachable range — and the most common in specialty.

High acidity
Light body
Origin-forward

Medium-Dark

~225–230°C

Roast flavors begin to dominate. Chocolate, caramel, and nut notes take over from origin character. Lower acidity, fuller body. Often preferred for espresso and milk-based drinks.

Low acidity
Full body
Espresso-friendly

Dark

~235°C+

The roast is the flavor. Origin character is largely gone — replaced by bitter, smoky, and charred notes. At this level, the quality of the green bean matters very little. It's a style choice, not a quality signal.

Bitter
Smoky
Roast-forward

Gradient of roasted coffee beans from light to dark brown.

ROAST PROFILE

The journey matters as much as the destination

Roast level tells you where a roast ended. Roast profile tells you how it got there — and that is where the roaster's craft actually lives. Two coffees roasted to the same final temperature can taste completely different depending on the rate of temperature rise, when heat was applied, and when it was pulled back.

Rate of rise

Speed of heating

How quickly the bean temperature climbs through each phase of the roast. A steep rate of rise builds momentum early — too steep and the outside develops faster than the inside. Too shallow and the roast stalls, producing flat, baked flavors with no clarity.

First crack

~196°C

Around 196°C, the bean expands rapidly and audibly cracks — releasing steam and CO₂ as internal pressure builds. This marks the start of light roast territory and the beginning of the most critical phase of the roast. Everything from here is a deliberate decision.

Development time

Post first crack

The window between first crack and the end of the roast. Too short and the coffee tastes underdeveloped — grassy, sharp, hollow. Too long and it goes flat and baked. Most specialty roasters aim for development time to be around 20–25% of the total roast duration.

Second crack

~225°C+

A second, quieter series of cracks as the bean's cell structure begins to break down under continued heat. This is the entry point into medium-dark and dark roast territory. Oils start migrating to the surface. Pushing past second crack means trading origin character for roast character — a line most specialty roasters don't cross.

SANDBOX APPROACH

Omniroast

Sandbox standard

At Sandbox, roasting is a transparent step. Not the moment where flavor is added, but where the flavor already present in the green bean is carefully unlocked. That means staying light, staying close to origin character — and having enough confidence in the coffee to not engineer it twice.

Most roasters produce two versions of the same bean: a lighter profile for filter, a darker one for espresso. We don't. Every coffee in the Sandbox lineup is roasted once, to a single profile that works across both. Not because it's easier, but because if a coffee needs to be pushed darker to function as espresso, we'd rather find a better coffee.