Safe Cleaning Methods for Low-E Glass and Hard-Water Residue

What cleaning routine do you use for low-E glass, particularly when the coating may be on an exposed interior surface?

I’m trying to separate ordinary residue from actual coating or insulating-glass damage. For example, a white mineral film from hard water may need more than a standard glass cleaner, but I’m concerned that vinegar, ammonia-based cleaner, a razor blade, abrasive pad, or melamine sponge could scratch the glass or affect a low-E coating. Labels and adhesive residue raise a similar question, especially if a new window still has manufacturer stickers on the glass.

The details seem important:

- Is the unit double-pane or triple-pane?
- Which surface has the residue: room side, exterior side, or between the panes?
- Was the glass cleaned with a commercial glass cleaner, diluted vinegar, dish detergent, or something stronger?
- Was a scraper, steel wool, abrasive sponge, or other tool used?

My starting point would be a soft microfiber cloth, clean water, and a small amount of mild, non-abrasive detergent, followed by rinsing and drying with another clean cloth. I’d avoid scraping unless the glass manufacturer specifically permits it. I also wouldn’t assume that haze between the panes means the argon escaped or that the insulating-glass seal has failed. Condensation or residue on an exposed surface can look similar.

What signs distinguish removable mineral deposits from scratches, coating damage, or seal failure? If the haze remains between the panes, or if the coating appears blotchy or discolored after cleaning, is that normally a glass-unit replacement issue rather than a cleaning issue?