If you mean the dark/black ring or buildup around a bathroom or kitchen faucet, it’s usually caused by hard-water deposits, soap residue, mildew, or grime.
Try this first
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Soak a cloth or paper towel in white vinegar.
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Wrap it around the dark area and leave it for 15–30 minutes.
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Remove the cloth and gently scrub with an old toothbrush or soft sponge.
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Rinse thoroughly and dry with a microfiber cloth.
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For stubborn mineral buildup, make a paste of baking soda + a little water, gently scrub, then rinse.
Important: Don’t use vinegar on natural stone countertops (such as marble or granite) because acid can damage the surface. Also, never mix vinegar with bleach.
If you tell me whether the faucet is on stainless steel, ceramic, granite, marble, or another surface, I can give you the safest method for that material.
