· Michael Blair
Middle Tennessee water leaves calcium behind as it evaporates. On glass that becomes a bonded deposit that detergent does not touch, and left long enough it etches the surface permanently.
Deposit or etching
Deposit sits on the surface and comes off with acid and dwell time. Etching is the glass itself having been attacked, and it cannot be cleaned off.
The test is simple: if a descaler applied and left improves it, it is deposit. If nothing changes, it is etched.
Removing deposit
An acidic descaler — citric, acetic or a purpose-made product — applied and left to dwell, then agitated with a non-scratch pad and rinsed.
It usually needs repeating on heavy build-up. Dwell time does more than scrubbing pressure, which risks scratching.
- Acid descaler with real dwell time, not more scrubbing
- Non-scratch pad only
- Repeat rather than increase pressure
- Protect frames and seals from the acid
- Squeegee after every shower to prevent recurrence
Etched glass
Professional polishing with cerium oxide can improve light etching. Deep etching is not recoverable and the panel needs replacing.
That is the argument for dealing with spotting early rather than living with it for years.
Preventing it
On shower glass, a squeegee after each use is by far the most effective habit — scale forms as water evaporates, so removing the water removes the mechanism.
On windows, redirect any sprinkler hitting the glass. A water softener addresses the source across the house.