Hot Pots And Glass Surfaces: A Cautionary Tale

Whether you can put hot pots on top of glass is a highly debated topic. Some people claim that they have put hot pots on their glass cooktops without any issues, while others warn that it can cause the glass to crack or shatter. The concern is that the sudden heat from a hot pot on a cold stove could damage the glass. Additionally, scratches on the glass surface, which can be caused by placing hot pots directly on the glass, can weaken the glass and lead to possible cracking. To avoid potential damage, it is recommended to use a trivet, potholder, or towel between the hot pot and the glass surface.

Tempered glass may shatter with hot pots

Tempered glass is more durable than regular glass, but it can still shatter. When tempered glass shatters, it is usually due to one of the following reasons:

Spontaneous Breakage

Spontaneous breakage can occur when the edge of the glass has been previously damaged. Over time, as the glass is exposed to different temperatures and elements, it will expand and contract, and the stress from this movement can cause the glass to shatter. While this may happen suddenly, the root cause is usually minor damage to the edges of the glass.

Binding in the Frame

Frame-related breakage is common and usually occurs when the glass is subjected to spontaneous shattering. As the glass expands and contracts, if there isn't enough space within the frame, the resulting stress will cause the glass to shatter.

Internal Stress from Nickel Sulfide Inclusions

Nickel sulfide stones can form during the glassmaking and handling process when using stainless-steel machines. Over time, these stones can change structure, causing internal stress that surpasses the strength of the tempered glass, leading to breakage.

Defective Tempered Glass

Defective tempered glass may have pre-existing cracks and scratches that weaken the glass. While tempered glass doesn't break easily, a strong enough impact can create cracks and scratches, eventually leading to breakage.

Thermal Stress

Glass is a poor conductor of heat, and when exposed to sudden temperature changes, different parts of the glass will expand and contract at different rates. This creates stress points that can cause the glass to crack or shatter. For example, placing a hot pot on a cold glass surface can cause the inside of the glass to expand rapidly while the outside remains cool, resulting in stress points that lead to cracking or shattering.

Therefore, while it may be tempting to place a hot pot on a glass surface, it is important to consider the risks of doing so. The convenience of placing a hot pot directly on a glass surface may not be worth the potential hazard of shattered glass. It is recommended to use protective measures, such as placing a trivet or hot pad between the hot pot and the glass surface, to prevent potential damage and ensure the safety of those nearby.

Pyrex and borosilicate glass can handle temperature gradients

Borosilicate glass is made up of about 15% boron trioxide, which is the ingredient that makes it resistant to thermal shock. It has a much higher proportion of silicon dioxide in comparison to regular soda-lime glass (80% vs. 69%), which makes it even less susceptible to fractures. This means that it can go straight from the freezer to an oven rack without cracking. For example, you can pour boiling hot water into borosilicate glass to steep tea or coffee without worrying about shattering or cracking the glass.

Pyrex was initially made from borosilicate glass when it was introduced in 1915. Since then, borosilicate glass and Pyrex have been used interchangeably. However, it is important to note that today, not all Pyrex is made of borosilicate glass. Some Pyrex products have switched to using soda-lime glass, which is more cost-effective but less resistant to thermal shock.

Scratches on glass may cause cracks and other issues

There are three main categories of scratches: superficial scratches, surface scratches, and sub-surface scratches. Superficial scratches are challenging to see and are usually only visible from certain angles. These can be repaired at home using DIY methods. Surface scratches are more noticeable and can be felt with a fingernail. These scratches require the attention of a local glass repair professional.

Sub-surface scratches are the most severe type and can easily be felt with your fingertips. These scratches often lead to window cracking and severe breaks, so it is imperative to hire a glass professional to address them. If you ignore deep scratches or cracks, the entire glass item can rapidly break, increasing the risk of injury to yourself or others.

To prevent scratches from becoming cracks, it is important to address them promptly. Several DIY methods can be used to repair light scratches, such as using toothpaste, pumice soap, nail polish, baking soda, or glass polishing products. However, for more severe scratches, it is best to consult a professional glass repair service.

In addition to causing cracks, scratches on glass can also affect the structural integrity of the glass. This is especially important to consider when dealing with window glass or other types of glass that are responsible for providing support or protection. Over time, scratches can weaken the glass, making it more susceptible to breakage or deformation.

Furthermore, scratches can also impact the optical properties of the glass. This is particularly relevant for applications where clarity and transparency are crucial, such as windows, eyeglasses, or camera lenses. Scratches can cause distortions or refractions in the light passing through the glass, affecting visibility and potentially compromising the functionality of the glass.

Aluminium may leave particles on the glass surface

Aluminium is a chemical element with a great affinity for oxygen, which means it readily forms a protective layer of oxide on its surface when exposed to air. This oxide layer is what makes aluminium generally resistant to corrosion. However, this oxide layer can be destroyed by contact with mercury or with salts of some electropositive metals.

When aluminium is heated and comes into contact with most non-metals, it can form compounds such as aluminium nitride (AlN), aluminium sulfide (Al2S3), and aluminium halides (AlX3). Aluminium also has a high chemical affinity for oxygen, which makes it suitable for use as a reducing agent in the thermite reaction.

If aluminium is heated and comes into contact with glass, it is possible that particles of aluminium oxide could be left on the glass surface. This could occur if the glass has a crack or imperfection that exposes it to air, allowing the formation of aluminium oxide. Additionally, if the glass is at a high enough temperature, it could cause the aluminium to melt and stick to its surface, potentially leaving aluminium particles behind.

It is important to note that the risk of aluminium leaving particles on a glass surface will depend on various factors, such as the temperature of the glass and aluminium, the duration of contact, and the specific type of glass and aluminium involved.

Trivets can be used to prevent scratches and cracks

Trivets are an effective way to prevent scratches and cracks on glass surfaces, especially when dealing with hot cookware. Trivets are heat-resistant pads or stands that act as a barrier between the hot item and the glass surface. By using a trivet, you can avoid direct contact between the hot pot or pan and the glass, reducing the risk of scratches, cracks, and other types of damage.

When choosing a trivet to protect your glass surfaces, it is important to select the right material. Soft materials like silicone or cork are ideal as they provide a cushioning effect and are less likely to scratch the glass. These materials are also heat-resistant, ensuring that they can withstand high temperatures without causing damage to the glass. Avoid using hard materials such as cast iron or steel, as these can potentially scratch or damage the glass.

In addition to material, consider the size of the trivet. It should be large enough to accommodate the pots and pans you typically use. Placing a hot item on a trivet that is too small can cause heat to transfer to the surrounding glass and potentially lead to cracks or damage. A trivet with a non-slip surface is also beneficial, as it provides stability and prevents the hot item from sliding or tipping over.

When using a trivet, follow these additional tips to prevent scratches and cracks:

• Avoid sliding or dragging pots and pans on the glass surface. Lift them away and set them down gently on the trivet.
• Keep the glass surface clean and free of debris. Use a soft cloth or sponge and mild soap or glass cleaner to wipe away any spills or grease. Avoid abrasive cleaners or scrubbers that can scratch the glass.
• Regularly scrub the bottoms of your pots and pans to remove any grease or burnt food that could transfer to the glass.

By using trivets and following these precautions, you can effectively prevent scratches and cracks on your glass surfaces while enjoying the convenience of placing hot items on your counters or stovetop.

Frequently asked questions