Grinders are very sensitive tools, so you should make small changes when you adjust the grind setting. These changes are called micro-adjustments. Making regular micro-adjustments to compensate for slight shot time errors of 2 or 3 seconds is preferable to waiting until a significant problem becomes apparent and your shot times are as much as 10 or 15 seconds away from your target range. This approach is like guiding your car down the motorway; to stay on the road you need to make frequent, small adjustments to the steering.
Large adjustments of the grind setting, called macro-adjustments, are required when something major changes in the way you make your coffee. For example, you may begin using a completely different recipe or you may get a new blend or single-origin from your roaster. When major recipe changes are made, you risk wasting a huge amount of coffee.
The problem: When you ‘adjust’ your grinders, it is a ‘blind’ change. It’s not like steering a car, where you can see which way the car is pointing. Making large changes to the grind setting is difficult because you don’t know exactly what will happen until you have made the espresso and timed how long it took to brew.
The solution: Be sure to keep track of the finest and coarsest settings your grinder has been on in recent weeks. In the training room, you can use a marker pen or apply two stickers to identify the maximum and minimum grind setting so new baristas know where the outer markers are. This is analogous to painting the bright lines on the edge of a roadway that make it obvious to drivers when they are at risk of drifting off to the side.
Video: How to make macro- and micro-adjustments
Understanding Grind Retention
All grinder designs take a little time to dispense the coffee they have ground.