The art of the glass detective

Featured Article
20 Dec 2018

As Featured in GGP Magazine - 2016

Phil Brown, European regulatory marketing manager at Pilkington United Kingdom Limited, part of the NSG Group, looks at the origins of glass breakages and best practice for identifying causes and providing solutions.

Television viewers love detective shows.  Victorian murder mysteries, brooding Scandi noir and gritty American thrillers – the popularity of crime drama as a genre remains as high as ever.

Investigating a glass breakage may not be as gripping, but it is important for customers, clients and building occupants that the cause is identified and a solution found.

The glass detective may work alone – whereas many modern day TV sleuths tend to operate in pairs – but he has a bag of tricks that helps make solving the mystery easier.  Generally, in addition to appropriate PPE for construction sites or buildings, a kit for inspections may include a laser gauge, coating detector, tape measure, steel rule, camera, magnifying lens, compass, feeler gauge, penknife, pen and notepad.

Finding the culprit

Like any good detective, it pays to ask lots of questions about the background to the problem.  Knowledge of activities taking place in or near to the glass, any recent unusual events or changes, and remedial or maintenance work on site can all paint a picture as to what may have occurred.

Locating the origin of the breakage is vital, as it will contain crucial evidence.  It’s almost the equivalent of finding a fingerprint at the scene of the crime!  The glass should be examined from both its surface and its edge to gather as many clues as possible.

A magnifying glass is essential for examining the glass, both on the surface and looking through the edge. The break pattern should be inspected to hone in on the failure origin, following the branching of the crack, for example, often leads back here. 

Inspecting the fracture area

From the surface, the source of a fracture or breakage can sometimes be found by identifying the point of branching - occasionally seen as cat’s eyes (two characteristically shaped pieces of glass).  Keep an eye out for these cat’s eyes, as they are a tell-tale sign of the origin.

The fracture area should be inspected, searching for rib marks and hackle lines, which should lead back to the failure origin.  When looking at the edge around the fracture, the presence of a highly polished mirror region can provide an estimate of the stress level in the glass at the time of fracture. 

If the glass that has broken is toughened, then the glass detective may be unfortunate in finding that most of the fragments have fallen from the frame and ended up on the floor.  In some instances, if the detective is very unlucky, a cleaner may have swept them away and with it the all-important evidence.  If the fragments are still present, then it’s a case of getting down on your hands and knees to search for the fragments containing the origin.

Causes of glass fracturing

There could be a number of causes of glass fracture, including impact damage (deliberate or accidental), edge damage before installation (during handling), poor installation (e.g. tight glazing, missing setting blocks), poor design (e.g. insufficient clearances, structural movement), inclusions in the glass and thermal breakage.

Some fractures are easier to detect than others.  For example, thermal breaks typically run from, and are perpendicular to, the edge of the glass. Others may be more difficult to identify without viewing under a microscope in a laboratory and, if an inclusion is suspected, may require subsequent chemical analysis.

The mysterious case of the glass breakage is unlikely to feature in a box set any time soon, although I would happily subscribe to it!  However, the clued-up glass detective can help to establish the likely cause of fracture which can play an important role in settling disputes in the supply chain and agreeing solutions.