Have you ever worked really hard to try and shatter safety glass so you would prove your point that nothing should be taken at face value? When he unveiled the Cybertruck, Tesla’s CEO and product architect Elon Musk was practically giddy to demonstrate the toughness of this show-worthy-futuristic-looking vehicle.

  • A 9mm bullet shot at the body won’t make a dent: check
  • A sledgehammer repeatedly struck at the body won’t make a dent: check
  • The truck can tow a 1,400 lbs. charge: check
  • A steel ball won’t break the metal windows… oops!

One explanation Musk graciously offered is that the sequence of events was off: the sledgehammer stunt compromised the integrity of the glass. The edges were cracked, which weakened the rest of the glass panel and rendered it prone to breakage.

If you pay attention, however, you will notice the windows shatter in a spider web-like pattern typical of safety glass, adding the necessary security dimension to daily life as opposed to breaking into small, sharp and dangerous pieces. Should tempered glass break, it will do so in small pebble-like pieces that are easier to sweep up than shards of regular glass.

In this article, we’ll briefly describe how tempered glass is produced, and why it matters when you choose sliding glass doors for security and safety.

Patio with frameless glass doors

The Science Behind Tempered Glass (a.k.a. Toughened Glass)

The concept of glass tempering traces back to 1874, when Francois Barthelemy Alfred Royer de la Bastie submerged nearly molten glass in a bath of cooler oil. The patented process (England, 1874) may have inspired chemists and engineers to experiment with other types of lamination and techniques to strengthen glass and expand its uses in a more secure and safe way. Whomever we should credit with the invention, it boils down to enhancing glass’s strength properties through thermal treatment.

Today, the process consists of placing the panels of glass on a roller table, submitting it to extreme high heat (1,047°F or above), and following that with a quick cool down. The shock of the temperature change creates tension and has a “locking effect” on resistance and durability, making tempered glass the preferred material for applications that demand heightened security:

  • Car windows
  • Sliding and patio doors
  • Shower doors and bathroom windows
  • Swimming pools and other athletic venues
  • Public areas such as exhibition venues
  • Common household items (table tops, shelves, cabinets, fireplace screens, etc.)

Frameless Glass Door Security and Safety: The Cover Glass Commitment

Building codes across the United States require tempered glass be used in specific scenarios, taking into consideration the distance from the floor, the room in which it is used, etc.

Cover Glass is committed to offering the strongest sliding glass doors on the market in respect for its clients’ security and safety, regardless of location in the house. Because we want our clients to receive all the benefits of our frameless sliding glass doors without worrying about potential weak points, we opted for the Rolls Royce of toughened glass panels (sorry, Tesla!).

Laminated glass sandwich two tempered panels via the SentryGlas™ process, developed to withstand hurricane might. The make-up is referred to as tempered and laminated glass, resulting in a 1/2” inch-thick product that is 5x stronger than standard tempered glass.

Because tempered glass cannot be cut, each sliding panel is produced to order, ensuring utmost strength on its own and in combination with other sliding panels, in any configuration that suits our clients’ needs. 

If many go by the motto “better safe than sorry” (and so do we), we’d like to add “better secure than sorry.” Adding to the strength and resistance of our frameless glass doors – be it natural event or malicious purpose – we add a locking system on the inside of the top and bottom of the first panel. It is virtually impossible to tamper with our tempered sliding doors and windows!

Untitled design (9)-1

How Can You Tell Tempered Glass From Standard Glass?

How do you tell a koala bear from a panda bear? Short of grabbing a baseball bat and whacking the window (an activity we do not recommend), there are noticeable differences between tempered glass and standard glass.

  • The edges of tempered glass are smooth and clean, where the edges of standard glass may look and feel scuffed. One usually receives sliding glass doors or windows already in their frame, which makes examining the edges a tad tricky. Cover Glass offers true frameless sliding doors, so checking the temper characteristic is a breeze and you won’t have to try any of the following tricks.
  • Scoring annealed glass will create a clean line. In fact, scoring deeply then snapping along the score is how you cut ordinary glass. If you score toughened glass, the line will be slightly chipped, flaky and uneven. As mentioned above, you cannot cut tempered glass panels, unless you submit them to high heat, which removes the temper (and defeats the purpose).
  • Safety glass must be identified as such with a discreet etching (known as “the bug” in glazier’s jargon) on at least one corner of each panel. 
  • The high-pressure tempering process leaves dark lines on the glass that are indiscernible to the naked eye. If you look through polarized glasses, you will notice those marks, which are the result of the panel going through the rolling table.

When you go through the process of beautifying your home with glass doors, you don’t want to choose between aesthetics and security. You are entitled to both style and peace of mind, regardless of use, no matter the room’s location or its accessibility to intruders or exposure to extreme weather. 

Cover Glass proudly presents the best sliding glass doors for security, safety, and dramatic effect.


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