Have you ever stopped to wonder what causes glass to shatter? Glass is everywhere, in our homes, cars, electronics, and even our furniture. And while it’s often tough and resilient, it’s also a material with surprising fragility under the wrong conditions.
Certain types of glass, such as toughened and laminated glass, are specifically designed to be impact resistant. These types of glass undergo specific processes to enhance their strength, making them more capable of withstanding significant impacts without shattering into dangerous shards, thus offering enhanced safety benefits. In this blog, we’ll break down the science behind glass, explore the common causes of shattering, and give you tips on how to prevent it from happening unexpectedly.
What is Glass?
To understand what causes glass to shatter, you first need to know what glass is.
Glass is a solid, non-crystalline material made primarily of silica (sand), along with other ingredients like soda ash and limestone. Unlike metals or plastics, glass doesn’t have a regular internal structure. It’s an “amorphous solid,” meaning its molecules are arranged more like a liquid frozen in place.
What Causes Broken Glass?
Sudden Impact
Let’s start with the most obvious cause- impact.
When an object hits glass with enough force, it creates a shockwave that spreads through the material. If the force exceeds the internal strength of the glass, it breaks. Surface damage from these impacts can create stress points that lead to glass shattering.
Thermal Stress
Have you ever poured hot water into a cold glass and seen it crack instantly?
That’s due to thermal stress — when one part of the glass heats or cools faster than the other. This causes uneven expansion or contraction, putting stress on the glass. When glass cools too quickly, it can lead to internal stresses that may result in spontaneous breakage.
Common scenarios include:
- Pouring boiling water into a cold glass or mug, causing the glass to expand and contract unevenly.
- Leaving a glass tabletop in direct sunlight, where different temperature zones can create stress points.
- Oven doors or glass cookware breaking after being removed from high heat, as the glass cools and contracts rapidly.
Defects
Sometimes, glass breaks for no apparent reason. You might wake up to a shattered shower door or see a glass table suddenly explode. When that happens, manufacturing defects are often to blame. This is why choosing a reputable manufacturer like us at UKO Glass is important.
Here’s what might go wrong:
- Nickel Sulfide Inclusions: Tiny particles trapped inside tempered glass during production can slowly expand over time, eventually causing spontaneous shattering.
- Internal Stresses: Glass that wasn’t cooled evenly during the tempering process may have built-in internal stresses.
- Scratches or chips from the factory or during transport can weaken the structure.
The annealing process can lead to variations in the chemical composition within the glass, creating internal tension that may cause the glass to crack or shatter over time.
Tempered glass, which is designed to shatter into small, less dangerous pieces, is especially prone to spontaneous breakage if any flaws are present.
Structural Pressure
Even without a sudden impact, glass can break if it’s under constant stress from its surroundings.
Examples include:
- Window panes installed too tightly in frames.
- Uneven weight distribution on a glass shelf.
- Wind pressure on large windows or glass facades.
- Warped frames or incorrect installation.
Over time, the tension builds up, creating tensile stress within the glass. This compressive stress on the surface and tensile stress in the centre, is crucial for the glass’s strength. However, if the stresses exceed the inherent strength of the glass, it can eventually lead to breakage. This can happen weeks, months, or even years after installation.
Spontaneous Breakage
Spontaneous breakage, also known as spontaneous glass breakage, is a phenomenon where glass breaks without any apparent reason or external force. This can be alarming and dangerous, but this is where choosing the right glass comes in.
When choosing the right glass for your needs, consider using safety glass, such as laminated glass. Toughened glass is heat-treated to be stronger and shatter into small, less harmful pieces, while laminated glass consists of layers that hold together when shattered, providing enhanced safety for both architectural and automotive applications.
How to Prevent Glass from Breaking
To prevent glass from breaking, it’s important to be mindful of sudden temperature changes. For instance, avoid pouring boiling water into a cold glass, as the rapid change in temperature can cause the glass to expand too quickly and result in cracks or even shattering. Similarly, when using oven-safe glassware, always let it cool down gradually before washing. Exposing hot glass to cold water creates significant thermal stress, which weakens the structure and may cause it to break.
Environmental factors also play a role in glass durability. When installing glass in frames, it’s essential to leave adequate space for expansion. This prevents tensile stress from building up as the glass responds to temperature changes, especially from the heat generated during manufacturing or from seasonal fluctuations.
Never place heavy objects on unsupported glass surfaces, as this can introduce internal tension. If the stress surpasses the glass’s natural strength, it may result in cracking or breakage. For added protection during installation, always use rubber padding or spacers. These materials help absorb pressure, reduce vibration, and allow for slight movement, minimising the chance of damage.
What Causes Glass to Shatter?
Glass shatters when internal stress or external factors cause it to break. That stress can come from a sudden impact, rapid temperature change, manufacturing flaws, improper installation, or even long-term wear and tear. By understanding causes and taking preventive steps, you can protect your home, your belongings, and yourself from the stress of unexpected glass breakage.
At UKO Glass, we offer an unbeatable range of glass products, including tempered glass for safety, and quality double or triple glazed units for windows and doors. Whether you’re looking for safety glass or oversized glass units UKO Glass has the perfect solution for you. For more information email us on theteam@ukoglass.co.uk or call 01422 861116.