Æ 1.07 Recap & Glossary

Recap

• Extraction in espresso occurs only at the surface of particles  — this is called erosion
• This means a fine grind is required, and the smallest particles are especially important in extraction
• Grinders exert two kinds of force on coffee: compression and shear
• Different grinder types apply these forces in different ways
• The grind size from any grinder isn’t uniform, but a distribution of different sized particles
• Small particles contribute a disproportionate amount of the surface area for extraction, while larger particles play an important role in allowing sufficient flow through the puck
• Grind shape also plays a role in extraction that is not yet well understood
• Grind size distributions are measured in the laboratory using laser diffractometry
• Baristas can measure grind size distributions directly using the new Barista Hustle app