Given the amount of stress the average safety glass rear window is under at all times, it can shatter suddenly if there's even minor damage to the edges or interior of the glass. From the outside, however, the damage appears to occur for no reason whatsoever.
Spontaneous glass breakage is an extremely rare occurrence, however it is a possibility. There are a few reasons that glass would break without impact and the two main ones are nickel sulphide inclusions or thermal shock (also known and thermal stress).
Thermal Stress:
Because glass is a poor conductor of heat, thermal stress can cause it to shatter by itself. It expands and contracts at a slower rate than the air around it.
A cracked mirror can be based on temperature and humidity changes. The severe temperature change could also make a hairline crack cause failure. Happens to lots of old windshields in the winter.
In some cases, a windshield may shatter seemingly without cause; but there is always a reason. Sometimes, a windshield may have a small crack or chip which can grow due to extreme temperatures or mechanical stress. If these issues are not repaired, a windshield may shatter – seemingly out of nowhere.
Considerable stress can build around chips, cracks, or other imperfections in the edges of a tempered glass window. Over time, environmental stressors like temperature, wind, and road vibrations can put those glass imperfections under even more stress, which triggers spontaneous breakage.
During extreme temperature fluctuations, these layers expand or contract at various speeds. This produces tension within the windshield, which might lead to a windshield crack. This is more likely to happen in very hot or cold temperatures. You are especially vulnerable if you turn on the heat or air conditioning.
Excessive pressure on the mirror, especially its edges or corners, can lead to cracks. It might happen while moving, installing, or placing heavy objects near or against the mirror. Temperature Changes. Sudden or extreme changes in temperature can cause the mirror to expand or contract, leading to cracks.
Extreme Temperatures
The glass may expand and contract to a breaking point in extreme temperatures, such as in freezing weather or scorching heat. For example, tempered glass can withstand up to 480 degrees Fahrenheit before shattering.
A broken mirror in house is not considered good. According to Vastu, breaking a mirror is often considered a negative omen. Here's what it signifies: Negative Energy: Mirrors are believed to reflect energy, and a broken mirror may signify the presence of negative energy or an imbalance in the home.
If glass isn't installed properly with a sturdy, supportive framework and sealed to avoid moisture and airflow, it's prone to breaking on its own. Excessive weight from the glass itself or pressure from wind and weather can also stress the glass beyond its breaking point.
Spontaneous glass breakage doesn't happen often, but because it is unpredictable and there may be other hard-to-determine contributing factors such as poor edge fitting or quality, it is not usually something that glass manufacturers cover under warranty.
A very uncommon reason why a glass table might shatter for no reason is due to Nickel Sulphide particles becoming trapped in the glass. Over time, this can cause them to expand, resulting in the table breaking. Sudden temperature changes can expand the chipped glass and break the glass.
Stress from temperature changes.
If you live in an area where the temperature can change quickly, it could cause your rear window to shatter. If you are exposed to extremely hot or cold temperatures, it can cause the class to expand and contract.
Rapid swings from cold to hot (or vice versa) can cause a windshield to crack.
On average, you can expect to pay an average cost of $100 to $400 to replace your windshield, a side window, or rear car window. Classic and exotic vehicles will be more expensive. Small, triangular side windows can also be more expensive due to the difficulty of installation.
Is Spontaneous Glass Breakage Normal? While rare, spontaneous glass breakage does happen sometimes in double-paned windows, due to the pressurized gas between the panes. It can also happen to tempered glass, which is a tougher type of glass that has been treated with heat and chemicals to withstand high impacts.
Under specific circumstances, yes, your windshield could shatter if it has a crack that compromises its integrity. However, it won't shatter and spray tiny shards of glass all over the inside of your vehicle because windshields are made from laminated glass.
The exact temperature at which glass will break varies depending on the type of glass and its thickness. It also depends on the rate at which the temperature changes and the structural integrity of the glass itself. Generally, thin, regular glass starts to crack when heated at about 302°F (150°C).
If you are using mirror glass behind a heat source (an oven or fire for example) it must be toughened. Mirror glass that is exposed to heat will crack if it is not toughened.
Epoxying is considered to be the most effective in repairing a glass crack thanks to its two-part resin and hardening solution, but simpler methods like plastic, nylon, tape, and polish can get you by. For large cracks, you'll want to replace the window entirely.
Temperature fluctuations are one of the main reasons windshields crack overnight. A significant drop at night and then a rapid rise around noon can cause the glass to expand and contract, resulting in cracks.
Car windows can shatter for no apparent reason or due to thermal contraction/expansion stresses. It is also caused by manufacturing defects and “object hits.” However, the spontaneous shattering of a car window can be unnerving. This is especially unnerving if it happens while you are driving.
Comprehensive coverage on a car insurance policy may help pay to repair or replace your windshield if it's cracked or shattered by a rock. Another coverage, called full glass coverage, may also be available to help protect you against the cost of fixing or replacing a windshield.