Start with a pumice stone before the acid.

Yes — for light calcium scale on hard, smooth surfaces like glass tile or ceramic, a pumice stone is the safest and most effective first step. Wet the stone, scrub gently, and the scale comes off without etching the tile.

For heavier scale, muriatic acid (diluted 1:10 with water in a plastic bucket) is the go-to. Apply with a sponge or sprayer, let it sit 30–60 seconds, then scrub with a nylon brush. Do not use a wire brush. Rinse thoroughly with a hose and neutralize with baking soda afterward. Wear rubber gloves, goggles, and old clothes — acid burns are no joke.

Avoid acid on natural stone, colored grout, or any surface you’re not sure about. Test in an inconspicuous spot first. The commercial “scale removers” are usually just buffered acid blends — they’re gentler but cost more. They work fine if you’re nervous about mixing chemicals.

For scale on plaster or pebble finishes, leave it to a pro. One wrong acid wash and you’ve got a textured moon surface.