Scientists have derived the formula for the perfect espresso

It's about the physics of the brewing process.

Details

When brewing espresso, pressurised water passes through a layer of tamped coffee - the so-called "pak".

It is this process that determines the flavour of the drink.

Scientists decided to find out what the passage of water through this layer depends on.

To do this, they:

• ground the coffee to different sizes
• packed it at different densities
• created 3D models of the coffee structure using X-ray scanning
• modelled the movement of water inside

It turned out that a key role was played by:

• coffee particle size
• packing density
• the number of "connected" voids between the particles
• total surface area

From this, the researchers derived an equation that allows them to predict how the water will pass through - and therefore how the drink will turn out.

Why it matters

Today, espresso making is largely built on experience and constant tweaking of parameters.

The scientists note:

• the new model could reduce the number of experiments
• help baristas fine-tune grinds and pressures
• could be used in "smart" coffee machines

It's not about a "one-size-fits-all recipe," but a more accurate understanding of the process.

Background

The process of a liquid passing through a porous medium has been studied in physics - it's called filtration theory.

Now these principles have been applied to coffee.

Source

The study is based on analysing the structure of ground coffee using X-ray tomography and modelling fluid movement. The work has been published in Royal Society Open Science (2026).