Every bag we sell carries an altitude figure, and most people read straight past it. It is the single number that tells you the most about how a coffee will taste before you ever open the bag.

Cherries ripen more slowly at altitude. Cool nights slow the plant down, sugars accumulate over a longer window, and the resulting seed is denser and harder. Density is what gives a roaster something to work with — it lets us push heat into the bean without flattening the acidity that makes it interesting.

Below about 1,200 metres you tend to get softer, rounder coffees with lower acidity. Between 1,600 and 1,900 metres the fruit starts to sharpen. Above 1,900 the acidity can become structural rather than decorative — it holds the whole cup together as it cools.

None of this makes high-grown coffee automatically better. It makes it different, and it makes it harder to roast. A dense Kenyan lot punishes an underdeveloped roast far more obviously than a soft Brazilian one ever will.