Why a clean grinder matters
Coffee is oily, and old oil goes rancid. When stale grounds and oil build up inside a grinder, every fresh dose picks up a flat, slightly rank note that no bean can overcome. You paid for good coffee; the grinder is feeding it through last month's residue.
Cleaning also keeps the burrs cutting cleanly. Grind consistency is the single biggest lever you have over taste, and gummed-up burrs grind unevenly.
A simple cleaning routine
1. Unplug the grinder and empty the hopper of beans.
2. Run it briefly to clear remaining beans from the burr chamber.
3. Remove the upper burr if your model allows, following the manual.
4. Brush out loose grounds with a stiff dry brush. Never use water on the burrs.
5. For a deeper clean, run grinder cleaning tablets through, then grind a small dose of beans to clear residue before your next brew.
How often to clean
A quick brush-out every week or two keeps most home grinders happy. Do the deeper tablet clean every one to three months. If you grind oily dark roasts, lean toward monthly, because they leave residue much faster than light roasts do.
Switching between very different beans? A quick clean in between stops the old flavour carrying into the new bag.
Signs your grinder is overdue
Stale smells from the burr chamber. Caked grounds around the burrs. Grind times creeping up. A flat, papery taste in coffee you know is fresh. All of these point to built-up oils and fines.
None of them mean the grinder is dying. In almost every case a proper clean brings it back, which makes cleaning the cheapest upgrade you can give your coffee.
What about rice?
You'll see uncooked rice suggested as a cheap substitute for cleaning tablets. Skip it. Rice is much harder than roasted coffee, it strains the motor, and some grinder makers void warranties over it. Tablets cost a few dollars per clean and are made to crumble like coffee while soaking up the oils.
A dry brush and the occasional tablet run is all a home burr grinder really needs.