VisionMSD-Sliding-Door-Gridscape-SliderImagine taking a nice, hot shower after a busy workday. You feel so relieved as the water trickles down your body. But suddenly….BOOM! The shower glass door explodes spontaneously.

Or better still, imagine having a great night’s rest. Then at about 1 a.m., you hear an explosion come out from your bathroom. As you jump up from your bed to investigate the issue, you see that your shower glass door has fragmented into millions of pieces.

These scenarios have probably not happened to you. However, the problem of shower glass doors exploding undisturbed is well-documented. Even though it’s very unlikely to happen to you, knowing what causes it and what to do if it occurs is handy knowledge to have.

Understanding the Properties of Different Glass Types

The process of glass-making goes back to over 5,000 years. And since then, different techniques have been used in their production. Here are the two most common:

Annealed glass

During the manufacture of annealed glass, the glass is left to cool slowly. This makes the glass stronger, more durable, and less likely to break. However, when broken, it breaks into large, jagged edges, which can cause significant injury to people. Due to safety concerns, building codes prohibit their use in areas susceptible to human impacts, like in shower glass doors. This brings us to the second type of glass.

Tempered Glass

In tempered glass production, the glass is cooled very rapidly to increase the strength of the glass, making it four to five times as strong as an annealed glass. But more importantly, tempering changes the property of the glass so that when it breaks, it shatters into blunt smaller fragments, compared to the sharp shards associated with annealed glass. This makes them safer as they are less likely to causes injury – and that’s why they’re referred to as ‘safety glass.’ Hence, shower glass doors are typically made from tempered glass.

A Cause for Concern

Unfortunately, the production process of tempered glass also gives it an unwanted attribute: the ability to explode spontaneously! According to a Tempered Glass Safety Alert published in 2018 by the U.S. Consumer Products Safety Commission, there are about 500 cases of shower glass doors exploding annually.

When reports of this phenomenon started to surface, shower glass manufacturers acted in skepticism, believing the claims to be widely exaggerated. They believed that because of the small space in bathrooms, a falling glass sounded like an explosion. Therefore, what happened was that the shower glass fell and broke – not exploded spontaneously. However, this explanation could no longer hold water when eyewitness accounts were overwhelmingly in support of the ‘spontaneous explosion’ phenomenon.

Next, shower glass manufacturers blamed improper installation as the main reason for the explosion. But contractors, who were not ready to take the blame, pointed to the fact that the hinges and frames often remained in place and undamaged after such explosions occurred. Hence, the nature of tempered glass is to be blamed.

Why Shower Glass Door Explode Spontaneously

As it turns out, shower glass doors can explode due to the nature of the tempered glass itself, as well as improper installation.

Nickel Sulfide Inclusion

Nickel Sulfide inclusions are a known issue for toughened glass, resulting from the presence of nickel contaminants in the glass melt reacting with sulfur, most likely from the furnace fuel. With time, the inclusion can grow, and this can cause stress in the glass. As a result, external stresses like heat can cause the glass to explode.

It is for this reason that some glass manufacturers conduct heat-soaking on the manufactured glass. In this process, the glass is heated in a chamber to temperatures higher than what nickel sulfide can withstand. If the nickel sulfide contaminants are too much, the glass explodes and fails the test. Glasses that pass the test are unlikely to explode spontaneously. However, due to the high cost of this test, only a handful of manufacturers conduct it.

Susceptible Edges

As noted early, heat-treating is what gives tempered glass increased strength. However, this strength is mainly to withstand direct impact. That’s why your shower glass might not break even if you throw a baseball on its face.

However, tempering makes the glass more susceptible to side impact. Consequently, a small side-chip in the glass may drive the entire glass to shatter.

That’s why shower glass doors must be properly installed. If not, the door may slip out of its hinges or off its track when opened. Also, ensure that the hardware and frame are well-secured. But most importantly, regularly inspect the glass edges for cracks and chips that may result in spontaneous breakage.


Thankfully, spontaneous glass explosion occurs so rarely that you’re two times more likely to be struck by lightning. Therefore, that shouldn’t deter you from installing one. And even if it does occur, there’s no need for panic. All you need to handle the situation is a simple broom and dustpan.

If you’re in the Salt Lake City area, curious about glass shower doors, please don’t hesitate to reach out to us for more information. We look forward to hearing from you!

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