Some people are skeptical about using a glass pitcher for holding boiling water and hot beverages such as coffee or tea. It is a reasonable prerogative as many of us have experienced pouring hot liquid into a glass container and ended up breaking it. But this is not always the case.
Specifically made to withstand high temperatures, the best glass pitchers can hold hot drinks for a long time, and they will not crack. With extra care, you can even pour boiling water into these glass pitchers without shattering them.
Why Does Glass Crack with Hot Water?
A generic glass pitcher, made of ordinary glass, undergoes expansion when subject to heat. Once you pour boiling water into the glass, the inside part of the glass expands due to heat while the outer layer remains cool. The temperature difference will cause the inner layer to expand far greater than the outer part.
The discrepancy in the amount of expansion between the inner and outer parts will create stress, which at some point will exceed the glass’s tensile strength. Once exceeded and the glass can no longer contain the pressure, also known as thermal shock, it will start to crack.
Why Some Glass Pitchers Don’t Crack
To be on the safe side, always use heat-resistant glass pitchers for your hot beverages.
Typically constructed of borosilicate glass, which is known to have a very low thermal expansion coefficient, they are more resistant to thermal shock than other glassware. They will not break under extreme temperature changes.
The coefficient of thermal expansion indicates the rate at which the glass expands when exposed to heat. The higher it is, the greater the tendency of the glass to react to heat by expanding. With a low thermal expansion coefficient, borosilicate glass can withstand high temperatures without drastically changing its shape, area, volume, or density.
How to Prevent Glass Pitchers from Cracking
The effect of thermal shock is powerful and results in the cracking of glass. Even heat-resistant glasses like Pyrex can shatter when poured with boiling water incorrectly. To prevent the glass from cracking when exposed to boiling water, you should avoid extreme and abrupt changes in temperature. You can accomplish this in different ways.
Pour the boiling water gradually
By pouring the hot water into the glass pitcher gradually, you will allow the glass to adjust slowly to the water’s high temperature, reducing thermal shock.
Use a metal spoon
Metal is an excellent heat conductor. When you put a metal spoon in the glass pitcher and slowly pour the water over the spoon, it will absorb some heat. This helps cool down the water that contacts the glass’s inner layer, minimizing its temperature deviation from the outer layer.
Warm up the glass
Another effective way to prevent breaking your glass pitcher when putting boiling water into it is to warm it up first. Before filling the glass, rinse it with 50% tap water and 50% boiling water; the outer layer first, then the inside part. By exposing the outside to heat, you let it expand before pouring the entire boiling water into the bottle, which means less thermal shock.
Shatter-Free Glass Pitcher
Pouring boiling water into a glass pitcher can be tricky. The key is to reduce the temperature difference between the inner and outer layers. By minimizing thermal shock, you can enjoy a no-worry, shatter-free pour.
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