Il Molino with the CoffeeMeister

Last week, you may recall, we started tackling the old Italian concept of the "four Ms" necessary to make espresso, with an introduction to la macchina. It's only fitting, then, that today we cozy up with la macchina's best buddy: il molino or la machinadosatore, the espresso grinder.

To put it in terms of that Neil Simon classic, "The Odd Couple," your grinder is to your espresso machine as Felix is to Oscar: It's precise, acute and fickle, while la macchina's less prone to acting than reacting.

Generally speaking, the espresso machine will do pretty much the same thing every time you turn it on: Push hot water through coffee at a certain amount of pressure. However, that isn't to say that the same thing will happen every time you give that water the green light. Why? Because the coffee's always changing.

That's where il molino comes in.

Roasted coffee is a very volatile ingredient, susceptible to even minor tweaks in temperature, moisture and light. Not only that, but it significantly changes as it ages (which is why fresh-roasted coffee is always worlds better than old stuff). All these things affect the way your ground coffee responds to the hot water forced through it by the espresso machine, with the flow slowing down or speeding up through the grounds depending on the changes in their makeup.

This is why high-quality espresso grinders are able to make practically limitless adjustments in the size of the particles they can create. To make those adjustments, a barista will turn a knob or rotate a metal collar on the grinder that either pushes the machine's burrs, the internal pair of razors that do all the chopping and grinding, closer together or pulls farther apart.

By making the grind setting finer, with the burrs sitting closer together, the barista can slow down the flow of water through the coffee. By making that grind coarser, she can speed it up. A barista may have to make these changes dozens (!) of times throughout the course of a shift, constantly chasing that elusive God shot.

Sadly, a startling number of baristas are told by a (well-meaning, I'm sure) boss, trainer or manager to never touch or make adjustments to the espresso grinder, even under threat of death. This "set it and forget it" tact, however, is contrary not only to the nature of the beans themselves, but also to the design of their dutiful grinder. (If the grinder wasn't meant to be adjusted, why would the burrs be movable at all?) The more fitting barista's adage might actually be "move it or lose it."

"But what about the coffee?" you're asking yourself. We'll find out next week, when we tackle the third "M" of the process.

Erin Meister trains baristas for North Carolina-based Counter Culture Coffee and sporadically maintains the blog Meet the Press Pot from her home in New York City. This is part of a series for the caffeine-addicted.