When the glass suddenly breaks: why it happens and how to be safe

SINGAPORE: Chinese New Year is just around the corner and hot pots will be a popular option on dining tables.

People who recall an incident last year, however, might be more careful with the team than before. A “steamboat” dinner with friends made headlines last January after a glass-topped table broke 30 minutes into the meal.

It’s one of several home glass breakage incidents that have circulated on social media, including one in 2018 after a shower glass door broke on a young child.

Most recently, social media user Joshua Lim escaped with minor injuries when a glass pot exploded on his stove.

She was boiling water to sterilize her baby’s milk bottles, but had left the pot unattended. When he returned, the water level was low. Then he poured tap water, “and then boom.”

“Everything was shattered,” he said. “I spent a good five minutes frozen on the spot. Like what just happened? How am I going to clean this up? Fortunately, the baby was outside. “

His family had used the pot for years, for example, to make stews. So he didn’t see this mishap coming.

But glass can break when you least expect it, so the Talking Point program finds out why and what can be done about it.

GLASS KITCHEN

In Lim’s case, materials science expert Leonard Loh from the Nanyang Polytechnic School of Engineering can shed light on what happened.

“Glass is brittle and it is also a poor conductor of heat,” he said. “A sudden change in temperature puts stresses on the glass and that can cause the glass to fail.”

To demonstrate this, the senior course director heated a glass beaker to 300 ° Celsius and added tap water, which was around 25 ° Celsius. The glass cracked and shattered, in what is called a thermal shock.

Still, this is unlikely to happen at home, as glassware doesn’t tend to heat up at such high temperatures, he noted. Most glass cookware is also made from borosilicate glass, which doesn’t expand or contract as much as regular glass.

In addition to borosilicate, glass cookware in Singapore is made from tempered soda lime glass or a glass-ceramic blend, also designed to withstand changes in temperature.

So why did Lim’s pot break? Another factor could have been at play: if your glass cookware has micro cracks or small chips, it may not need such an extreme and sudden temperature change to break.

GLASS PANELS

Microcracks, so small that they are invisible to the naked eye, can also spread over time in glass panels.

Over the past decade, it was reported that at least 530 exterior glass panes in residential and commercial developments were broken. That doesn’t even include the shower glass panels.

Talking Point glass installers spoke to estimate that 50 percent of glass breakages are due to improper handling and installation.

This includes installing the wrong size glass pieces for the support frame and being careless during the transfer and installation process.

“You have to be very careful with the edges … the weakest part of the glass,” said glass specialist Don Tay of Grab Glass.

“In the case of a slight bump, (the edges) can come off. It can break all the glass. “

When your workers handle glass panels, they never place the edges directly on any hard surface.

When a panel is attached to its metal frame, the edges are permanently cushioned by placement blocks to prevent rubbing against the metal; otherwise the constant friction will chip the edges.

However, according to Tay, customers have no way of checking whether a glass panel is installed correctly.

“Please go to professionals rather than general contractors, as professionals are the experts in handling glass and ensuring glass quality,” he advised.

TEMPERED GLASS

Both glass cookware and glass panels can be made from tempered glass, classified as safety glass because it breaks into small pieces with rounded edges and is therefore less likely to hurt people when broken. .

Point out why Lim escaped with a cut on his finger and a small hole in his shorts. If your planter was made of regular glass, it would have been broken into pieces with sharp edges.

Tempered glass is made by heating normal glass in an oven that is between 650 ° and 700 ° Celsius. This softens the glass.

Then cold air is blown to cool the outside of the glass faster than the inside, thereby compressing the surface and creating tension inside. Glass becomes four to five times stronger than normal glass and its breakage pattern changes.

CLOCK: Why even tempered glass breaks (3:09)

However, starting in 2011, the authorities tightened regulations for the use of tempered glass for safety barriers and at heights of 2.4 meters or more.

It turns out that the process of tempering the glass can cause spontaneous breakage.

“Normal glass contains impurities. And most of the impurities in the glass itself are safe, except for one type of impurity, which we refer to as nickel sulfide, ”said Quality Assurance Manager Chua Teck Huat of Singapore Safety Glass.

Unfortunately, nickel sulfide only affects tempered glass. The tempering process makes nickel sulfide unsafe.

If the impurity is present, it will be trapped as the glass cools quickly. Over time, nickel sulfide can expand and form microcracks that can cause glass to break without warning.

Singapore Safety Glass can test its products for nickel sulfide, Chua said. But you can’t monitor mishandling, neither during transportation nor during installation, in the same way.

LAMINATED GLASS

However, there is an alternative to tempered glass: laminated glass, which is formed by joining two pieces of glass with a piece of plastic, known as polyvinyl butyral, in the middle.

If one piece of the glass breaks, the other piece can hold the whole assembly in place, preventing it from falling and injuring people.

Singapore National Security Council Vice President Fong Kim Choy recommends the use of laminated glass as shower panels and doors. But it costs about twice as much as tempered glass.

“Let’s say it is too expensive for them to trade this for laminated glass; they can simply put a security film on both sides. That will also keep the broken shards or the broken pieces of glass together, ”he said.

For safe handling of glass at home, he cautioned against stacking glassware as that can chip the edges. But if necessary, cushion each piece with cardboard or fabric.

Also, breakage of tempered glass shelves in the refrigerator is “common,” so do not place hot items on them.

“First cool the food a bit before putting it in, and remember not to drop heavy containers like stews,” he advised.

EARLY DETECTION

To prevent more accidents, one person helping to design robots that can clean and scan glass panels for cracks is Mohan Rajesh Elara, assistant professor of engineering product development at Singapore University of Technology and Design.

The idea is that these robots warn end users in advance so they can take action like replacing a pane of glass.

The robots use artificial intelligence to detect and classify cracks. But there are limitations at the moment: glass is transparent, so robots can mistake elements in the surrounding environment for a crack.

To combat this, Mohan is working to add acoustic and thermal sensors, as the cracks reflect sound differently and retain more heat. This means that robots should be able to see, hear and feel.

“With robots doing the work, they can do it 24 hours a day, 7 days a week … which will be difficult if done as a manual process,” he said.

However, it will be about two years before these robots can be commercially deployed. In the meantime, increased safety awareness may be needed, even if not all the reasons why glass suddenly breaks are under our control.

“The best we can do is take note of the type of glass we are using and how we are using it,” said Talking Point host Steven Chia. “If you also notice chips or cracks in them, replace them.”

Check out this episode of Talking Point here. The program is broadcast on Channel 5 every Thursday at 9:30 p.m.