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Glass Restoration


By Dan Reynolds, PCM Estimator & Project Manager | March 12, 2015

Photo compliments of Presto Restoration Products.

Glass can be beautiful when clean and clear, and most property owners and managers will regularly have their windows washed using standard window cleaning materials (soap and water) and procedures to keep it this way. However, these individuals may at one point wonder why their standard window washing has become ineffective in cleaning their windows. Is it poor practices by the window washer? Possibly. However, it may likely be the case that their glass has become corroded or stained to a degree beyond standard cleaning solutions.

Glass Corrosion

What many do not know is that in time glass can corrode and leave behind stains, marks, and cloudiness that can be very displeasing to the eye and difficult to remove. The staining typically goes unnoticed at first because it takes time for the corrosion process to transpire, and can occur due to many factors. If left unsolved the problem can prove to be very costly in the end. Corrosion occurs when water is allowed to remain on glass for a short period of time. In short, WATER + GLASS = STAINING. When hydrogen (water) ions react with sodium ions from soda –lime-silica glasses, stage 1 corrosion occurs. The good news is staining from stage 1 corrosion can likely be cleaned with specialized treatments.  If this corrosion is allowed to continue for just a short time pH levels will increase and this increase in alkalinity can cause more damaging reactions. If the alkalinity reaches pH levels above 9, stage 2 corrosion occurs. This involves an attack on the silicate network of the glass and the breaking down of its molecular structure. If a white haze is left after stains have been removed, it is likely that glass is in stage 2 corrosion and glass replacement may be necessary.

The key to take from this:

  • Stage 1 Corrosion can typically be restored.
  • Stage 2 Corrosion is unlikely to be restored and replacement of glass may be necessary.

The main factors causing staining on glass/windows are:

  • Hard Water/Mineral Deposits
  • Oxidization
  • Acid Rain (Rain mixed with pollutants)

Hard water stains may appear as white teardrop shaped stains or streaks. They can occur by water running down the building façade and windows below, water deposits from sprinkler systems, and acid rain falling on windows. Staining from these sources may not be removable with standard window washing procedures. Oxidization occurs over time as metal around windows, such as frames, is exposed to water or humidity and deteriorates. The oxidization then runs over and infiltrates the windows causing staining and damage. It appears as hazing or a white etched look. With the use of specialized treatments and experience, glass with any of this type of staining may be restorable. However, please note that these treatments are not to be used on mirrored or tinted glass. It is important not to let the corrosion process go unchecked before the glass reaches a point of no return.

Essentially there are 3 options:

  • Do Nothing and Replace All Glass
  • Clean and Restore All Glass
  • Combination of Both Restoration and Replacement

The goal of glass restoration is to significantly save on the countless dollars that it would otherwise cost to replace windows. Upon completion of window restoration, it is important to consider protecting windows by applying a sealer which can delay or avoid similar stains from reappearing. There are many products available for this purpose, with varying durations of protection.

Do you have glass restoration needs? Give us a call at (301) 595-3700. We’ll send one of our experienced Exterior Building Services estimators out to give you a quote.