Coffee Grinder Marker Test

The marker test is a burr-alignment check in which removable marker is applied to a burr’s contact surface and the burrs are brought into very light contact so the wipe pattern can be inspected. It can reveal uneven face contact, but it is only one diagnostic and should not be treated as proof that every aspect of grinder geometry is perfect.

What the wipe pattern shows

If marker is removed evenly around the burr face, the opposing burrs are making relatively even contact at that test position. If marker wipes from only one sector, one burr face may be tilted relative to the other, or the carrier, burr seating, debris, or mounting surface may be influencing contact.

What it does not prove

The marker test is most useful for checking face parallelism near burr touch. It does not fully measure radial concentricity, shaft runout, carrier play, burr manufacturing tolerances, or alignment under real grinding load. A grinder can show a respectable wipe pattern and still have other mechanical variables.

Test gently

Use a removable marker, keep the grinder free of beans, and approach burr contact carefully. Do not force the burrs together or run them hard against each other. Follow manufacturer-specific procedures because burr mounting and adjustment systems differ.

Before shimming

Clean burr seats and carriers first and confirm that burrs are installed flat and fasteners are tightened evenly. Unnecessary shimming can make a well-performing grinder worse. Alignment work makes the most sense when there is a real symptom—such as abnormal chirp, uneven wear, or inconsistent grinding—not simply because a grinder can be disassembled.

Watch: Espresso Outlet Marker Test and Burr Alignment

This Espresso Outlet walkthrough demonstrates the marker wipe test on a DF64 Gen 2 and shows how contact marks can be used to evaluate burr-face alignment.

See our Coffee Glossary and browse home coffee grinders for related grinder terminology.