Mineral scale can narrow showerhead openings and make the spray uneven. Cleaning works best when the scale is softened before the holes are brushed, rather than forced through with a sharp object.
Remove or bag the head
If practical, remove the showerhead with a protected wrench. Otherwise fill a sturdy bag with white vinegar or a manufacturer-approved descaler and secure it around the head without stressing the pipe.
Soak and brush
Allow time for deposits to soften, then brush the face and openings with an old toothbrush. Do not enlarge the spray holes with a pin.
Rinse the plumbing
Rinse the head thoroughly and run water briefly to flush loosened material. Replace the washer if the connection leaks, and avoid overtightening.
Prevent repeat buildup
Wipe the face occasionally and inspect the screen or flow restrictor if pressure remains poor.