That bottle of white vinegar under your sink can replace half your cleaning cabinet; cutting grease, dissolving hard-water stains, and leaving glass streak-free for pennies. But its acidity is a double-edged sword: use it wrong and you'll etch marble, dull hardwood, or strip your cast iron. Find out exactly which surfaces vinegar loves (taps, toilets, kettles, laundry) and which ones it can quietly ruin; plus easy tricks to banish that sharp smell for good.