Without knowing what caused the ring, it's a bit of a wild guess. White cleaning vinegar would clean a ring from scale (lime or other water impurities) as well as something caused by algae or fungus.
Use a Scrub Daddy sponge to work vinegar into the ring and rinse away afterwards.
Every time I clean my mirrors, they end up having tons of streaks and almost look worse than before I started. What could I use to clean them that won't leave streaks...
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Ive tried using a pressure washer, but all that did was damage the pavers. I’m guessing a 10% solution of hydrochloride acid, then hosing off, but then how to apply...
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Maybe with a rag dipped in bleach.
try a Mr. Clean magic eraser
Without knowing what caused the ring, it's a bit of a wild guess. White cleaning vinegar would clean a ring from scale (lime or other water impurities) as well as something caused by algae or fungus.
Use a Scrub Daddy sponge to work vinegar into the ring and rinse away afterwards.
Do not use anything abrasive as it will scratch the fiberglass. Krud Kutter on a microfiber rag should work.