The hard-water reference distinguishes mineral deposits from everyday smears. It describes diluted vinegar as one possible treatment for compatible glass because the acid can loosen those deposits. Working from the top downward helps control coverage and runoff during the process.

Mineral Marks Need a Different Response from Fingerprints

Compatibility still matters, particularly around protective coatings, stone, and metal fittings. Use an approved product where required and follow its contact-time directions. After treatment, remove the residue and dry the glass instead of allowing another layer of mineral-rich water to evaporate on it.

Hard-water deposits can remain on glass after ordinary surface dirt has been removed.