Here’s the easiest test in the world: Fill a clear glass with that cloudy water and wait. If the water clears from the bottom up after a minute or two — like a fog lifting over a tiny lake — you’re dealing with plain old air bubbles. If it stays cloudy forever, then we can start worrying about actual particles.
I once did this test with a glass of water so cloudy I thought I’d accidentally poured a latte. I set it on the counter, stared at it for ten seconds, and by the time I blinked, it was crystal clear. I felt like a magician who had just performed a trick on myself.
