Repairing damaged glass: Glass passes for new

Discovery of damage to installed glass during the final stages of construction presents a serious problem, adding costs and delays to handover. Scratching is common as a result of operatives manoeuvring equipment, vandalism, and careless cleaning of glass coated with grit and dust generated by the construction process. Spatter from cutting with an angle grinder or welding operations is another routine way for glass to become damaged. Surface staining caused by calcite deposits on the glass as a result of water run off from concrete and stone surfaces also requires specialist treatment for removal.

Due to lack of awareness many construction managers still believe they have no choice but to replace damaged panes in order to achieve practical completion or face financial penalties imposed by clients. However, a scratch removal technique pioneered 15 years ago by glass renovation specialists Reface has been gaining ground in the UK.

There are a variety of techniques on the market but the underlying method is to grind the area surrounding the scratch down to the scratch’s depth and then to polish the surface to restore an optimum level of clarity. Normally, accidental scratches are less than 0.05mm in depth, but can be much deeper. Using a scratch removal technique is feasible when the scratch depth is of a sufficiently small proportion to the overall pane thickness so as not to compromise the strength of the glass when the technique has been carried out.

The leading company in the market is Reface Ltd. Reface was formed 15 years ago, the process was carried out by hand using ultra-hard grinding compounds for scratch removal, this was an effective method, but costly, since the grinding and polishing was done manually. It could take a single technician an entire day to treat an area of glass measuring as little as 300mm by 300mm. In 2002, however, Reface researched and developed a mechanised process that enabled a technician to treat up to 10 times more surface area in a day than previously.

The advantage of Reface’s technique, according the MD Nick Covey, is that while speeding up the process with mechanisation, the firm retains the manual control of the technique that ensures a higher quality finish. Other mechanised techniques involve machines that attach to the pane through suction. These require an operative only for directional manipulation. Covey believes the disadvantage of this technique is the higher incidence of visible distortion (or bending of light) caused by the “dish”

or concavity introduced into the glass surface where it has been ground away to the depth of the scratch. Unskilled operatives do not have the necessary experience required to graduate the concavity, consequently distortion is introduced which is more noticeable than the original damage.

As members of the Glass and Glazing Federation Reface work to the GGF standards for visual quality in respect of surface faults. For flat glass units this means inspection from 2m for float glass and 3m for processed glass such as toughened and laminated. Scratches visible from these distances require treatment. Reface however will fully remove surface damage, not just reduce it to a level that cannot be observed.

To achieve their high standard of finish, Reface uses a sophisticated technique, their technicians receive a minimum of three month’s training to become proficient in the process. The process is two stages, the first step is a course of staged grinding, progressing from coarser abrasives to finer ones. The second step is polishing, using a powered, optical polishing machine and their proprietary polishing compound. A key part of the technician’s skill is judging how to vary the grinding and polishing stages to match the unique conditions of the glass surrounding the scratch.

The Reface process can be used on any type of flat glass, including toughened, float, plate, laminated and other specialized glass. The process can be used on internal and external faces of curved glass, as well. As the technique is based on re-surfacing the glass, the process cannot be applied to textured or frosted glass, or glass with a coating on the damaged side.

As a result of the Reface process, there is no detectable loss of strength or change in the fracture properties of the glass. Importantly, to date, all manufacturers of renovated glass have maintained their existing warranties following scratch removal.

Discovering scratches or other damage can constitute an emergency. Reface aims to carry out a survey within 48 hours of the call. An estimate will follow the next day and they endeavour to start within five days of receiving the order. Reface will offer a project price or can provide technicians on a day-rate basis to work under the client’s direction. Reface can organize its own access requirements if required. Its technicians are IPAF licensed for cherry pickers and scissor lifts, and PASMA licensed for erecting light alloy towers. Reface is also insured to work at any height externally.

With a client base including the biggest main contractors and developers in the country, Reface is growing quickly, having doubled its turnover and staff levels in the last three years. It will undertake work anywhere in the UK and Ireland and has also carried out projects in Europe and the United States. n