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| Classic meandering pattern of heat-related stress crack, accompanied by evidence of edge damage. In this case, the building had both: edge damage and underspecified glass. Reflective blinds and a South exposure combined to create a high frequency of this type of breakage. |
Glass Shower Doors Can Shatter Without Warning (Chicago): If your shower door is made of glass, you may endure injuries, a big clean up and thousands of dollars down the drain. CBS 2′s Dave Savini first exposed tempered-glass patio tables suddenly exploding. Now he found the same happening with shower doors. Dorothy Malinski’s shower door suddenly exploded while her mother was bathing. “I heard this big bang, this big boom,” said Malinski. “I couldn’t enter all the way because there’s glass all over the counter, in the sink, on the floor.” Her mother was cut on her hands and face.
Even though tempered-glass shower doors are supposed to break into small pieces — to prevent injuries from larger, sharper pieces of glass — they can break in bigger shards. That is what happened to Larry Kucharik, who was injured while cleaning up the shattered glass from his shower door.
“I just tapped the top of it and a chunk of it came down and hit my ankle,” said Kucharik, whose ankle is still scarred. “It started bleeding, and there was a lot of blood all over the floor.”
The U.S. Consumer Product Safety Commission reports more than 60 complaints of shower doors shattering for no reason — just suddenly exploding, causing lacerations and bleeding. People reported needing stitches and even surgery. Mark Meshulam, a glass and window consultant, reviewed the reports. “These are the types of injuries and situations that I would expect to see when something goes wrong with shower doors,” he says. He says a microscopic imperfection during the manufacturing process can grow and migrate, weakening the glass until it suddenly shatters. It can even shatter without it being touched. “I would say treat the doors gingerly,” Meshulam warns. “Do not bang them. Don’t allow children to hang on the towel bars.”
He also says look for chips near brackets, the towel bar and along the edges. Also, make sure the door only moves the way it is supposed to and is not loose on the track or hinges. In Larry Kucharik’s case, the manufacturer replaced his shower door at no cost. This has also been a problem at hotels. Meshulam says one reportedly had 50 doors shatter. He would like to see protective film on shower doors to catch breaking glass. This is a tempered glass problem, so it involves various door manufacturers and the ages of glass. If this happens to you, call the Consumer Product Safety Commission and the door manufacturer.
Also see here & here.
Chicago Window Expert - Mark Meshulam (pictured) is a consultant for glass breakage and expert witness for personal injury due to glass breakage. When tempered glass breaks, the energy retained in the glass due to internal tension/compression releases explosively and produces a breakage pattern sometimes called “cubes’.
Seeing a cubist breakage pattern does not tell you why the glass broke, it only tells you that the glass was tempered. Generally, there are three reasons tempered glass will break: impact, edge damage or inclusions. Inclusions are tiny impurities in the glass. The most well known are nickel sulfide, however there are also silica and gaseous inclusions which look like tiny bubbles.
Normally, when tempered glass breaks, it falls down into a pile of little cubes. Only the most patient window consultants with the most generous client would ever consider piecing the cubes together to determine the cause of breakage. That being said, I have personally spent many hours picking through the rubble looking for an important clue: a pair of adjacent hexagons, known as a butterfly pattern, that borders a nickel sulfide inclusion.
However, occasionally the pieces of broken tempered glass will stay in the opening, locked to each other like blocks in a masonry arch. And just like in a masonry arch, if you remove the keystone, the arch – or glass in this case – comes tumbling down. This picture above shows broken glass which was a part of a laminated unit. The PVB (polyvinyl butyrate) interlayer held the pieces in place, giving us an opportunity to observe that impact damage is visible, even in tempered glass.
Spontaneous Breakage in Tempered Glass: Glass, and especially tempered glass, sometimes breaks all by itself. This can be quite disconcerting when, as has happened in a public place which will go unnamed here in our great city, large, thick panes of tempered glass basically blew up fairly frequently. The unusual cause in this rare instance: the glazing contractor attempted to grind the edges of the glass after it was tempered, creating a series of time bombs. It is a very bad idea to modify glass after it is tempered!
A more well-known, but also quite rare cause of spontaneous breakage is nickel sulfide inclusions. If you read the previous post, you will already be down with the fact that glass is made from melted powders. A nickel sulfide inclusion is a tiny rock of unmelted material that remains in the glass. Below see an artists graphic representation of a nickel sulfide inclusion.
You can well imagine that a little rock embedded in a slab of glass which is under high tension/compression forces, could weaken the glass and eventually cause breakage. But the story gets worse. Nickel sulfide grows an additional 4% of its size over time, especially in the presence of heat. If it is located in the strata in the glass between tension and compression, and it grows, kaboom!
Exploding Glass Shower Doors: One of the scariest, yet somewhat common type of tempered glass spontaneous breakage is in glass shower doors. They are exposed to banging against bumpers, heat from the shower, wrenching action of through-mounted towel bars and of course, nickel sulfide inclusions. In hotels, multiply the risk factors by the number of rooms and the lack of care typically taken by a hotel patron. There can be a delay between impact and crack propagation in tempered glass, just like any other glass, and sometimes the time the glass finally explodes seems ironic and and Machiavellian. Quite often the perverted glass will explode while the unsuspecting victim is in the shower.
Let’s count the problems: 1. The victim is naked. 2. There are sharp cubes of glass projectiles flying around. 3. The victim is bare footed. 4. The victim must walk barefooted over a field of freshly shattered glass shards. So here’s a tip for readers who actually do take showers: If your shower door shatters, stand still for a moment and take stock of the situation. Hopefully you are not cut too badly. Without moving your feet too much, look for a towel. Try to grab it and lay it down on the glass so you can walk out. Then get the hell out and never shower again.
Stress Cracks (see head picture): A “stress crack” will usually only happen in annealed or heat strengthened glass. Stress cracks emanate from the edge of the glass and meander about apparently without purpose. But there is a purpose: to relieve stress. However, the term “stress crack” can be misleading. If annealed glass is subjected to thermal fluctuations beyond its capabilities, it will break in a way that will relieve the stresses induced by thermal changes. This type of failure is a design issue. Heat strengthened glass should have been specified for the application. However, there can be a near-identical breakage pattern which emanates from damage in the glass edge that fails as stresses, such as thermal, are applied.
To tell the difference between a true stress crack and a crack due to edge damage, look at the edge of the glass for a chip, which we window linguists call an “oyster”. You might have to look hard because the oyster could be buried in the primary seal on the #2 or #3 surface. Another clue would be the distribution of glass breakage in the building. It would be normal to find stress-like cracks on elevations with greater temperature swings. But does the breakage also coincide with the use of reflective interior blinds, especially in a partially opened position? That would be indicative of a true stress crack, rather than a crack induced by edge damage.
Seeing a cubist breakage pattern does not tell you why the glass broke, it only tells you that the glass was tempered. Generally, there are three reasons tempered glass will break: impact, edge damage or inclusions. Inclusions are tiny impurities in the glass. The most well known are nickel sulfide, however there are also silica and gaseous inclusions which look like tiny bubbles.
Normally, when tempered glass breaks, it falls down into a pile of little cubes. Only the most patient window consultants with the most generous client would ever consider piecing the cubes together to determine the cause of breakage. That being said, I have personally spent many hours picking through the rubble looking for an important clue: a pair of adjacent hexagons, known as a butterfly pattern, that borders a nickel sulfide inclusion.
 |
| If you look closely, you can see the point of impact on this tempered glass. A laminated interlayer holds the cubes in place. |
Spontaneous Breakage in Tempered Glass: Glass, and especially tempered glass, sometimes breaks all by itself. This can be quite disconcerting when, as has happened in a public place which will go unnamed here in our great city, large, thick panes of tempered glass basically blew up fairly frequently. The unusual cause in this rare instance: the glazing contractor attempted to grind the edges of the glass after it was tempered, creating a series of time bombs. It is a very bad idea to modify glass after it is tempered!
A more well-known, but also quite rare cause of spontaneous breakage is nickel sulfide inclusions. If you read the previous post, you will already be down with the fact that glass is made from melted powders. A nickel sulfide inclusion is a tiny rock of unmelted material that remains in the glass. Below see an artists graphic representation of a nickel sulfide inclusion.
 |
| Artists representation of nickel sulfide inclusion. |
Exploding Glass Shower Doors: One of the scariest, yet somewhat common type of tempered glass spontaneous breakage is in glass shower doors. They are exposed to banging against bumpers, heat from the shower, wrenching action of through-mounted towel bars and of course, nickel sulfide inclusions. In hotels, multiply the risk factors by the number of rooms and the lack of care typically taken by a hotel patron. There can be a delay between impact and crack propagation in tempered glass, just like any other glass, and sometimes the time the glass finally explodes seems ironic and and Machiavellian. Quite often the perverted glass will explode while the unsuspecting victim is in the shower.
Let’s count the problems: 1. The victim is naked. 2. There are sharp cubes of glass projectiles flying around. 3. The victim is bare footed. 4. The victim must walk barefooted over a field of freshly shattered glass shards. So here’s a tip for readers who actually do take showers: If your shower door shatters, stand still for a moment and take stock of the situation. Hopefully you are not cut too badly. Without moving your feet too much, look for a towel. Try to grab it and lay it down on the glass so you can walk out. Then get the hell out and never shower again.
Stress Cracks (see head picture): A “stress crack” will usually only happen in annealed or heat strengthened glass. Stress cracks emanate from the edge of the glass and meander about apparently without purpose. But there is a purpose: to relieve stress. However, the term “stress crack” can be misleading. If annealed glass is subjected to thermal fluctuations beyond its capabilities, it will break in a way that will relieve the stresses induced by thermal changes. This type of failure is a design issue. Heat strengthened glass should have been specified for the application. However, there can be a near-identical breakage pattern which emanates from damage in the glass edge that fails as stresses, such as thermal, are applied.
To tell the difference between a true stress crack and a crack due to edge damage, look at the edge of the glass for a chip, which we window linguists call an “oyster”. You might have to look hard because the oyster could be buried in the primary seal on the #2 or #3 surface. Another clue would be the distribution of glass breakage in the building. It would be normal to find stress-like cracks on elevations with greater temperature swings. But does the breakage also coincide with the use of reflective interior blinds, especially in a partially opened position? That would be indicative of a true stress crack, rather than a crack induced by edge damage.
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