During the past three years we have been constantly working on high profile glass buildings that are suffering from heavy glass contamination which will not come clean with just a soapy wash. In our experience, this level of contamination will only occur on glass which doesn’t have regular cleans as part of a maintenance strategy, resulting in lime scale build-up, or is situated in the vicinity of a building site, heavy traffic or a train station and has been subject high levels of airborne contamination.

When contaminants remain on the outer surface of the glass it is possible that the contamination will etch the outer surface, possibly due to sodium ion deletion.  The building contamination may contain cementacious dust, most likely from local building works.  Cement/concrete contains lime which is alkaline; the surface of the glass will be etched as a result of long term exposure to an alkaline so a chemical clean will combat this build up.

The only option may be polishing of the glass surface to remove the pits and fissures, creating a smoother surface. If the surface of the glass has been etched then the surface is essentially ‘rougher’ than when first produced on the float line.  The various pits and fissures which have been formed increase the angles at which the light is refracted, which in turn can create a haze like appearance.

We have completed a number of notable chemical cleans on large glass buildings. In London The Shard, which suffered a concrete spill during construction, resulted in all 11,000 glass units needing a chemical clean. We also cleaned St Georges Tower, alongside the river Thames, The Walbrook building which is opposite a large inner city construction site and Cannon Street station. We have also completed a chemical clean at Snow Hill in Birmingham above a station.

We can complete the clean by abseil or using the house BMU. The only issue when using the BMU to complete a large amount of chemical cleaning is damage to the basket; using chemicals over an extensive period will result in significant corrosion to the basket.

Our rope access equipment has been thoroughly tested with the chemicals we use. The chemical does reduce the strength of webbing, which is why we destroy all harnesses and ropes at the end of each chemical clean contract we complete and we monitor the exposure of the equipment continually.

An abseil clean is quicker than using a BMU and does eliminate BMU reliability issues and chemical damage and leaves the plant available for any other maintenance works that may be required.

Our chemical has been tested by a specialist glass consultant and has now been used on Permasteelisa, Gartner and SBV projects without affecting the glass warranty which is as important as removing the contamination in the first place.

For extreme staining which has etched the glass surface beyond the point a chemical clean will suffice, we can offer our polishing service which incorporates the use of our cutting edge paste, which is not only infinitely cleaner than using a traditional cerium oxide (pumice powder) it also provides a better clean and has non-distortive capabilities avoiding optical dishing in the polished glass.

Before each clean we conduct a free trial to ensure the best solution possible is used to bring the glass back as close to the factory finish as possible.

The following pictures are taken from a full scale facade mock-up to find the best solution to remove a concrete spill.