Hard Water Spotting

When hard water dries on glass, the water leaves and the dissolved minerals do not. What remains is a chalky deposit bonded to the surface — visible as cloudy rings or a general haze that survives repeated washing.

Why washing does not remove it

Ordinary glass cleaning removes material sitting on the surface. Mineral deposits are chemically bonded to the glass, so detergent and a squeegee pass straight over them. This is the most common reason a window looks no better after being cleaned, and it is usually mistaken for poor workmanship.

Removing established deposits takes a mineral-specific approach rather than more effort with the same cleaner.

The part that is not reversible

Left long enough, the deposits etch into the glass itself. At that point the damage is physically in the pane, not on it, and no cleaning process will restore clarity — the only remedy is replacing the glass. How long that takes depends on water hardness, sun exposure, and how often the glass gets wet, but it is a matter of seasons and years rather than weeks.

This is the reason hard water spotting is worth addressing early rather than tolerating.

Where it comes from

Lawn sprinklers hitting windows are the leading cause, and the easiest to fix — adjusting the spray pattern solves it outright. Runoff from concrete, stucco, or masonry above a window carries dissolved minerals down the glass. Well water is typically harder than municipal supply. And in this area, winter road salt spray adds its own version of the same problem on roadside properties.

If you have spots that keep coming back after cleaning, the useful conversation is about what is wetting the glass, not about the cleaning method.