Care of Toughened Glass

Scratching of Toughened Glass

For some years sporadic complaints have been received from window fabricators, builders and homeowners regarding scratching of glass in new housing.

Typically the scratching is associated with the initial clean carried out at, or prior to, hand over of new houses and is most obvious on toughened glass. Many of the instances are anecdotal and refer to replacements required for toughened glass only with normal annealed glass unaffected. This has led to a popular view that toughened glass is softer than annealed glass.  

This issue is gaining more importance due to the recent changes making double-glazing mandatory. This is increasing the replacement costs for damaged glass by a factor of three or more, resulting in Builders looking harder at the issue and associated liability.

Members receiving complaints relating to scratched toughened glass need to be aware of the following issues when fielding any of these enquiry’s:

• The surface hardness of glass is unaffected by the toughening process.
• The following extract discusses the issue of roller pick up:
• “TOUGHENED GLASS: The cleaning of toughened glass requires special care. The glass surface opposite the standards compliance stamp may, as a consequence of the manufacturing process, have ‘pickup’ on the surface. ‘Pickup’ is a deposit of very small particles of glass which are fused to the glass surface. A cleaning method which does not dislodge these particles should be employed otherwise scratching of the glass surface may result. Blades or scrapers have been known to dislodge ‘pickup’ from the glass surface. A soft cloth, which will not dislodge 'pickup’, should be used. It is suggested that professional cleaners consult with their suppliers as to the suitability of available cleaning equipment, materials and methods.”
• The amount of complaints where toughened glass has been badly scratched and where annealed glass in the same house is lightly or unaffected has suggested to some that there is a significant difference in the cleaning methodology required. This conclusion overlooks the fact that the toughened glass in the houselot is invariably in the larger windows which tend to have different cleaning techniques and equipment used when compared with the annealed glass used in the smaller windows typically in sashes and overlights. E.g. smaller higher windows will have less pressure applied and may not have squeegee blades used on them compared with lower level large picture windows.
• Most examples of scratching seem to be coming from the final Trade Clean process ie. Professional cleaners not home owners. Further investigation of these instances have found examples of poor practise and lack of training.
• It appears that most professional cleaners are not aware of appropriate techniques to use in these circumstances, commonly employing scrapers and blades, or even the existence of “pick up” in toughened glass.

Trade customers should be aware of the issues above and check that appropriate techniques are being used for the cleaning of glass.