Volume 35, Number 3, March 2000
Guess What? Glass Breaks!
while it is obvious to those in the glass industry, the consumer is harder to convince
by Dez Farnady
A few months ago I commented on the need to develop a healthy respect for glass. While it is a wonderful asset to our life and architecture, it can pose a variety of dangers we tend to ignore. The most obvious danger is the horrible cuts it can inflict when it breaks.
For those of us in the glass business, glass breakage is a fact of life due to the frequency and quantity of glass we handle.
While it is obvious to us, the extent to which the general public continues to ignore the reality of the fragility of glass continues to amaze me. I suppose we can consider it as yet another compliment to how well we have learned to make it.
The reason why breaks occur have changed. The latest discovery in the construction business is low-level thermal-stress breakage: Energy performance glass products are susceptible to this type of breakage which occurs when the temperature differential in a piece of glass becomes excessive. Performance tinted glass products limit heat gain by absorbing heat energy. Additionally, unusual shading patterns on the glass can create temperature differentials causing breakageusually in the form of long cracks perpendicular to the glass edge. This increased use of tinted energy performance products and lack of proper heat treatment cause breakage in commercial buildings for what appears to be no reason. Of course, the glass people are immediately accused of providing defective product, but thats another story.
Tempered glass is four times stronger than annealed glass. It still breaks from serious impact and will also break at what appears to be random unexplained moments only identified as that famous spontaneous breakage. Not only is the break spontaneous, but it is breaking into a jillion little pieces, so we still have not achieved perfection. We have, nevertheless, made the glass much more difficult to break and have prevented thousands of major injuries.
The places where breaks occur have changed. The most common breakage, and the most dramatic, is the impact break so ably illustrated in every chase movie in which the bad guy runs his car through a large lite of storefront glass. The old example of the neighbor boy putting a baseball through the kitchen window is no longer appropriate because boys no longer play baseball in the street. More likely, it is adults on a golf course who have broken the window on the house overlooking the eighteenth green. But the eternal home of impact breakage is still the abandoned warehouse where vandalism runs rampant.
The scariest break, for me at least, is the one where the shower door breaks. Although these incidents have been reduced by the requirement of tempered glass, one sure way to cause shower door breakage is with a bottle. For example, if you drink too much of what is not good for you, you will fall down in the shower and knock the door off its track or slam it against the frame. The mess caused by a bad mixture of alcohol, blood and water will look like a war broke out. Fortunately, the tempered glass cuts will look nastier than they are but will make a big enough mess to scare the perpetrator sober. The sober way to break a shower door only requires carelessness. Worn or missing bumpers leaving exposed metal to glass contact on frameless glass shower doors is one way to pop a piece of tempered glass.
The safety glazing laws passed a couple of decades ago have eliminated many dangerous glazing conditions that the horror stories of the past barely are remembered. Fortunately, the glass processing and installation techniques have also improved to the point where we almost dont even remember that it can break, so when it does we are taken by surprise. Nevertheless it still does break.
Dez Farnady is manager of architectural products for ACI Distribution in Santa Clara, CA. His column appears monthly.
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