Being hurt by broken glasses is an experience no one would ever want to encounter. The dangers imposed by pieces of broken glass imparted a lot of effort to manufacture the safest glass that we can use without worries. 

Could tempered glass be one of them? Exactly speaking, is tempered glass safe really? 

Tempered glasses are used in a variety of applications due to their safety and strength. They are stronger than ordinary glasses and can withstand blunt impacts that would shatter untempered glasses. If you manage to break them under a more intense impact, tempered glasses shatter into small pieces that cannot cause serious wounds even when you accidentally step on them.  

That said, the safety of tempered glasses lies in their ability to shatter into pieces under intense impact. But what gives them that trait? Here are some helpful facts you never knew about tempered glasses. 

Why does Tempered Glass Break in Small Cubes?

Strength is not the only thing that varies based on how glasses are made. There is another unusual characteristic that separates tempered glass from others – the way they break.

You have probably witnessed a car accident or watched a movie where a car gets smashed against something. Did you realize the glass in the car window didn’t break like the regular glass but instead, shattered into very tiny granular pieces? 

Why does that happen?

This trait is attributed to the chemical and mechanical process this type of glass undergoes during manufacturing. A glass, with nickel sulfide included, is tempered by heating at a high temperature then rapidly cooled to room temperature. 

They are crafted such that cooling takes place more rapidly at the center of the glass than on the surfaces. This causes contraction and tensile stresses at the center whereas compressive stresses are caused on the surface. The minimum surface compression is 10,000 PSI while the minimum edge compression is 9,700 PSI.

It is this compression stress that gives the tempered glasses the ability to break into pieces. The higher the stress, the smaller pieces that the tempered glass break into. 

Is Tempered Glass Easy to Break?

Due to the compression treatment these glasses undergo, they are not easy to break. Depending on the manufacturer, the force required to break tempered glass ranges between 20,000 to 24,000 PSI (or pounds per square inch). This means they are approximately four times stronger than a regular glass of the same thickness. 

In addition, tempered glasses are also treated with some chemicals such as hydrochloric acid during manufacturing to increase their strength. Due to this special treatment, tempered glass can withstand stress and bend further before finally breaking. 

That said, tempered glass is not easy to break, which is another safety feature. Think of it, you are driving home and your kid just through a golf ball hitting your windshield. If it were made of ordinary glass, it would shatter into sharp and dangerous pieces – exposing your kids to danger. But given that the windshield is made of tempered glass, it is unlikely to shatter into pieces – it may only develop cracks. 

 Are Broken Tempered Glasses Dangerous? 

Unfortunately, not all broken pieces of tempered glass are safe. Pieces of tempered glass can sometimes clump together when broken forming a cluster with abrasive and sharp edges. If these clumps of broken pieces of tempered glass scatter around, they can hurt and cause wounds if someone steps on them. 

In addition, it is also very possible to get cut by tempered glass with unfinished edges. I have witnessed this on a few occasions among installers at a fabrication shop near my workshop. They usually underestimate tempered glass’s ability to cut and would use their uncovered leg or arm to support the pane in place. Often I see a guy with his hand wrapped in gauze and if you inquire, he would confirm he has been cut by the glass – they usually deal with tempered glass. 

That said, when handling any type of glass during construction or installation, you should wear gloves recommended for handling glass. You can also wear protective sleeves to further protect your body. 

Is Tempered Glass Toxic?

Several studies have shown that some types of glasses contain potentially toxic levels of lead and cadmium. Most research on the toxicity of glasses is centered around tableware – drinking glasses and plates. 

Tempered glass as tableware does not contain lead and has no side effect on humans. Besides, tempered glasses are strong and are easy to clean since some are dishwasher friendly. Therefore, you can remove all the pollutants or any potentially toxic substance on the surface of the tempered glass tableware by washing. 

Is Tempered Glass the Same as Safety Glass?

Safety glass is a term used to describe a glass that is designed to cause less harm to individuals upon breaking. So, is tempered glass the same as safety glass? Yes, tempered glass can be used as a safety glass as well. 

I would say safety glass consists of two types: tempered glass and laminated glass (which can also be made by two tempered glasses). 

Tempered glass is a safety glass owing to the fact that it shatters into smaller pieces when broken. The smaller pieces are not as dangerous as the larger sharp pieces formed when an ordinary glass is broken. 

Tempered glass can also be laminated and used as safety glass. Laminated glass is two pieces of glass that are sandwiched and fused with a sheet of polyvinyl. If you were to hit this glass with an object, it would crack into something that looks like a spider web as shown in the picture, but not fall on the ground. 

With that said, tempered glass is mostly used in an environment where human safety is an issue.

What Are Some of The Applications of Tempered Glass?

As mentioned before, tempered glass is required as safety glazing in “Hazardous” application. Some of the applications include entrance doors, business buildings, racquetball courts, microwave ovens, showers, and tub enclosures, patio furniture, skylights, and lastly, side and rear windows of a vehicle. 

Liability is a big reason many people always choose tempered glass in the above-mentioned areas. A jewelry store would want to purchase display glasses made up of tempered glass so, in the unlikely event that the cases break, the tempered glass would protect the customers and the merchandise from injuries. Most consumers also prefer larger products be constructed with tempered glass because there is less of a chance that they would break during shipping.

The Bottomline

Tempered glass receives a special treatment during manufacturing resulting in a hardened thick glass. Upon breaking, it shatters into smaller pieces rather than large pieces. The idea is that the smaller granules of glass landing on exposed skin are likely to cause small knicks or superficial cuts. In comparison, non-tempered glasses tend to break into larger pieces and may slash your skin or cause a deeper cut if they accidentally land on exposed skin.