Meticulous x Lance Hedrick - Onboarding Part 3 of 6 - Coffee Puck Integrity & Resistance

In Part 3 of this onboarding series, Lance Hedrick moves from practical shot-pulling into the science behind espresso extraction. This video breaks down the core variables — flow, pressure, and resistance — and how grind size, roast level, and the coffee itself shape every shot. What you'll learn: -Flow vs. Pressure: How these two variables interact, and why pressure builds as flow rate drops early in a shot. -The Over-Pressure Valve (OPV): How a traditional 9-bar pump system works, and the OPV's role in capping pressure. -Why Resistance Changes Over a Shot: Why puck resistance steadily decreases as extraction progresses, creating the classic pressure dip-and-recovery curve. -Grind Size and Puck Integrity: How finer grinds increase resistance, and what "choking" the machine looks like on the graph. -Roast Level and Resistance: How roast level affects fines production and puck integrity, and how fines migration can build resistance late in a shot. -The Coffee Itself: How density and solubility differences between coffees (e.g. Ethiopian heirloom vs. Pacamara) affect grind requirements. By the end of this video, you'll have a solid grasp of the fundamentals behind espresso extraction. Filming Credit: @dennis.cobarrubias 00:00 Introduction 00:42 Traditional Espresso Basics 02:23 Pressure, flow, and resistance 07:10 Effects on the coffee puck and extraction 08:44 Grind effects on resistance 09:52 Roast level effects on resistance 12:29 Effects of the coffee itself on resistance 13:39 Wrapping up