Pouring Boiling Water Into Glass Dishes: How To Avoid Breakage

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Many people are skeptical about pouring boiling water or hot tea straight into a glass dish — and rightfully so. Poor-quality and non-tempered glass often tends to shatter and break when subjected to high heat. But that’s not always the case, and with a few tips, you can safely pour boiling water into a glass dish or container.

To avoid breaking a glass container or jar when pouring boiling water into it, you need to avoid a sudden change in temperature that could cause thermal shock. You can do that by pouring the water slowly, using a metal utensil to absorb some heat, and warming up the glass beforehand.

Let’s take a closer look at which types of glass are safe for boiling water and consider some tips to prevent the glass from shattering. We’ll also discuss why glass tends to crack from hot water.

Can You Put Boiling Water in a Glass Container? 

Pouring hot water from thermos into glass

You can put boiling water in a glass container made with tempered glass since it’s strengthened to handle the stress of rapid and sudden temperature change. But it’s still better to take a few precautions to reduce the chances of it shattering.  

Even something as heat-resistant as Pyrex (on Amazon) can crack or shatter if boiling water is poured incorrectly.

To prevent that from happening, you need to avoid a sudden change in temperature. Here are a few ways you can do that:

Pour the Water Slowly

When you pour hot water into the glass slowly, you give it the chance to adjust to the high temperature of the water. This reduces thermal shock. 

Use a Metal Utensil

Metal is a good conductor of heat, so when you put a metal utensil like a spoon or a knife in the glass and then pour water over it slowly, it’ll absorb some of the heat. 

As a result, the water that makes contact with the inner layer of the glass cools down, reducing the difference in temperature between the inner and outer layers.

Warm Up the Glass

You can also prevent your glass from breaking by warming it up first. To do that, rinse the glass with half boiling water and half tap water.

Do the outer layer first and then the inner layer. This way, the outer layer will expand before you pour the hot water into it, reducing thermal shock.

Can You Put Boiling Water in a Mason Jar? 

Pouring tea on blue background on blue wooden table with sugar and sweets

Yes, you can pour boiling water into a mason jar, and you can even put it in a pot filled with boiling water to sterilize it. Just make sure that the jar is at least at room temperature before placing it in the water. 

It’s even better if you let the jar heat up along with the water, instead of putting boiling water straight into a cold jar. If the jar is very cold, it might break if you put it into boiling water.

Why Does Glass Crack From Hot Water? 

When you put boiling water in a glass at room temperature, the inner layer will absorb heat and expand. And since glass is a poor heat conductor, heat conduction through the glass is slow. As a result, the inner layer becomes hot while the outer layer stays comparatively cold.

This difference in temperature causes the inner layer of the glass to expand much more than the outer layer. As a result of the difference in the expansion, the outer layer will experience a lot of pressure, and if it’s unable to handle that pressure, it will crack.

The sudden change in temperature, known as thermal shock, also causes internal stress on the material, which can ultimately break the glass.

Why Some Glass Doesn’t Break

Some glass, like borosilicate glass, doesn’t break from thermal shock. The glass is known for its low thermal expansion coefficient, which is why it’s able to withstand thermal shock better than other glassware and it doesn’t break when exposed to rapid and sudden temperature changes.

The thermal expansion coefficient is basically the rate at which the glass tends to expand when subjected to heat. The higher the coefficient, the more the glass will react to the heat and expand.  

But since borosilicate has a low expansion coefficient, it can handle high temperatures without drastically changing its density, volume, area, and shape.

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