Complaints to glass suppliers relating to scratched glass are common and claims are made that suggest that toughened glass scratches more easily than annealed glass. Frequently, the cause is found to be inappropriate cleaning of the glass. Also it is common for glass to be damaged because the builder has not taken adequate steps to protect the glass during construction. This article give some general advice on correct glass cleaning procedures. Specific advice on the cleaning of glass should always be sought from a reputable glazier or professional window cleaner before any glass cleaning is undertaken. Professional glass cleaners have significant experience and access to equipment, materials and methods which the general public may not.

Guidelines for glass cleaning
It is recommended that glass be protected from contamination caused by building materials and methods during construction as this will greatly simplify the glass cleaning task at the end of the project. If the glass is not protected during construction then the glass and frames should be cleaned frequently during construction.
Construction dust, leached from concrete and rusting from steel can contribute to the formation of mild chemicals, which may stain or otherwise damage the glass.
Glass should be cleaned using only cleaning materials which are free of grit and debris (to avoid scratching and marking of the glass surface).
Only detergents and cleaning solutions which are recommended for cleaning glass should be used. Mild detergents are preferable.
Extra care is necessary where high performance and special products such as self-cleaning and reflective glasses are installed. The coated surface can be susceptible to stains and scratches and therefore requires vigilance during the full construction process and require specific cleaning procedures. Refer to the manufacturers web site or product literature.
Temporary screens should be installed if welding, sandblasting, floor sanding, cuffing or other potentially damaging construction practices takes place near the glass.
Glass installations which are adjacent to concrete (e.g. concrete slab floors) require extra care and cleaning due to the abrasive nature of concrete dust.
All tradesmen should be advised to be aware of damaging glass and windows and to leave in place any materials protecting the window or glass.

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

What not to do?
Do not use cleaners which contain Hydrofluoric or Phosphoric acid as they are corrosive to the glass surface.
Do not clean the glass when the glass is hot or in direct sunlight.
Do not allow cleaning solutions to contact the edges of Laminated glass, Insulating Glass Units or Mirrors.
Do not store or place other material in contact with the glass. (This can damage the glass or create a heat trap leading to thermal breakage).
Abrasive cleaners, powder based cleaners, scouring pads or other harsh materials should not be used to clean windows or other glass products. Some tapes or adhesives can stain or damage glass surfaces. Avoid using such materials unless they are known to be easily removed.

If damage occurs!
If glass is damaged or broken on-site, ensure that experienced glaziers are engaged to rectify the situation. Glass can be a safety hazard if not handled properly.

Advice for Painters!
Paint spots have been traditionally removed using a sharp razor blade. The use of a blade can in some cases cause damage to the glass. As an alternative, investigate solvents or graffiti removal materials, ensuring that they will not damage the glass. If a blade or scraper is used then the risk of damage can be reduced by using a scraper which has a clean edge and is held at an angle of 30 degrees to the glass. However, surface coated, modified or tinted glass requires special care. Seek cleaning advice from your local glass merchant.

Care of mirrors
Mirrors require special care in cleaning. To clean mirrors, simply wipe over the surface with a few drops of methylated spirits on a damp cloth. Polish surface dry with a lint free cloth. Some proprietary glass cleaners, if used to excess, can cause damage to the silvering as can excessive amounts of water. Make certain when cleaning the face of the mirror that there is no contact with the silver backing, particularly at the edge of the glass and be careful to keep any moisture away from the paint backing of the mirror. Do everything possible to ensure that the cleaning cloths used are free of any abrasives.

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