Hard-water stains on glass: what causes them & how to remove them

What is a hard water stain?

While they may look like dirt on the glass, hard water stains are mineral deposits of calcium or magnesium left behind when water hits the glass and evaporates. Every drop that hits your windows can leave solids behind.

Why washing doesn't touch it

Soap and water clean dirt and oils off glass. Mineral deposits are different. They bond to the glass itself, so washing a pane with hard water stains won't actually remove the stains on its own.

When is the damage irreversible?

Left untreated for too long, mineral deposits can etch into the glass itself, causing irreversible damage. At that point, the only solution is replacing the pane. It takes years of wetting and drying, adding more hard water each year. Before it gets to that point, the mineral deposit sits on top of the window and can be removed. We happily treat hard water spots on windows.

What we do about hard water stains

• We start by test-treating a small area to see how deep the deposit goes
• We use specialized treatments and tools
• Once the stain comes out, we wash and dry your window completely so nothing new is deposited following our clean

Stop stains from coming back

Turn sprinklers away from your windows and schedule regular cleanings to avoid hard water stains from leaving a permanent mark on your glass.