Direct contact with a heat source can cause glassware to shatter. This is why it's important to preheat your oven before putting a baking dish inside and never put it on a stovetop or open flame. It's also important to never let your hot glass cookware come in contact with something cold, and vice versa.
Most glass will not tolerate that much heat and will break. Unless you have a PYREX glass bowl or pot, don't use glass on a stove.
It's not advisable to put a glass jar directly on the stove to warm it. Most glass jars are not designed to withstand direct heat and can crack or shatter due to thermal shock. If you need to warm a glass jar, consider these safer alternatives:
What temperature will stove glass withstand? Schott Robax woodburner glass will withstand temperatures of up to 760 degrees Centigrade, however with coal and wood this temperature can be easily exceeded - so try not to add too much fuel and keep the intake vent half to three quarters open.
Check to see if there is a marked "Oven-Safe" symbol underneath the piece. Glass bowls made of borosilicate or tempered glass and marked as oven-safe can go in the oven and withstand high temperatures. Those made of non-tempered glass may not be suitable with heat resistance and withstanding temperature changes.
Like most materials, glass expands slightly when heated up and shrinks the same amount when it cools down. If one part shrinks or expands faster than the part next to it, then the two regions tug against each other. This pulling, called “tension” in engineering, can be strong enough to shatter glass.
Heat Resistance Test
Carefully apply a small amount of heat, such as from a lighter flame, to an inconspicuous area of the glass for a few seconds. Remove the heat and check if the glass surface cracked — if not, it's likely tempered.
At What Temperature Does Glass "Break"? Glass bottles and jars are usually not affected by ambient, refrigeration, or warm temperatures. However, high heat (>300°F) and excessive thermal variations can cause glass to shatter or break.
One of the main causes of damaged glass or cracks is overheating. If the stove is burning too hot, the temperature can become so high that it causes the glass cracks or even crazes. To prevent overheating, it's important to make sure that you're using the correct fuel, correct size log and correct load.
Shattered cooktops happen when heat is trapped between the lid and the glass stovetop, creating a strong vacuum seal. The air gets forcefully sucked out, causing the glass to shatter. While this kind of “exploding” stovetop might not happen often, it's better to be safe than sorry!
Cookware will experience thermal shock when it rapidly changes temperature. This shock will make metal warp and glass crack. Obviously, having cracked glass near freshly cooked food is an undesirable outcome for any cook.
Shattering can also occur if you use Pyrex with direct heat sources. Do not use Pyrex glassware on the stovetop (either an open flame or electric burner), under the broiler, in a toaster oven or on a grill.
We do not recommend baking in any size or shape of Ball or Kerr canning jars. The glass used for Ball and Kerr canning jars is not tempered for oven use and is not meant to be used as bakeware. The jars are safe to use for home canning recipes, cold or room temperature food storage, cold beverages, and crafting.
Mason jars are designed to withstand high heats when gradually warmed in an oven or pot of water. But dumping boiling water directly into a room temperature glass jar creates a sudden, drastic jump in temperature that the glass cannot handle.
Excessive Heat and Temperature Changes
A similar effect occurs when substances, such as enameled cookware or plastic utensils, melt onto the glass. Thermal shock occurs when cool glass is exposed to sudden heat. A common cause of cracks is when hot pots are placed onto a cold glass surface.
Tempered glass is stamped with an identifier, which can be found in the corner of the sheet of glass. The identifier will show the manufacturer name and the CPSC (Consumer Product Safety Commission) standards, e.g. “CPSC 16 CFR 1201 CAT II”. This proves if the glass is tempered or not.
Glass does not reflect heat, but instead heat passes most of it through glass, with only small amounts absorbed (why many thermometers still use glass). This is why the heat from the sun passes through a window and can be felt on the inside of a house.
Tempered Glass can withstand constant temperatures of up to 470 degrees Fahrenheit. Tempered glass is suitable for fireplace glass where the fire is not near the glass. When tempered glass is exposed to sustained temperatures of greater than 470 degrees F, the structure of the glass gradually weakens.
The temperature differential that borosilicate glass can withstand before fracturing is about 330 °F (180 °C), whereas soda–lime glass can withstand only about a 100 °F (55 °C) change in temperature.
It completely melts/liquifies at approximately 1400 C to 1600 C depending on the composition of glass. Glass is made from a variety of substances, depending on the intent of use. Mostly sand, lime and soda are what most glasses are made of.
Severity: The greater the temperature difference between the hot water and the glass, the greater the risk of the glass breaking. For example, pouring boiling water into a cold glass is riskier than pouring warm water.
When a window pane of ordinary float glass is first heated, it tends to crack when the glass reaches a temperature of about 150 - 200ºC. The first crack initiates from one of the edges.
Tempered glass usually comes in two varieties: annealed and heat-strengthened. Annealed can withstand temperatures up to 250°C (482°F), while heat-strengthened ones have a maximum temperature rating of 350°C (662°F).
1. Borosilicate glass: Borosilicate glass is a type of glass commonly used in laboratory equipment and other high temperature applications. Among other materials, it is made from a mixture of silica and boron trioxide, making it highly resistant to thermal shock.