How to prevent your glass lunchbox breaking in the microwave

Описание: A couple in Taishan District, New Taipei, made headlines recently for a very unusual workplace accident. They were warming up their lunch in the microwave, and the glass lunchbox broke in two! As long-time regular microwave users, they were baffled. We spoke to a physics teacher to find out what would cause a glass container to behave so strangely, and what you can do to prevent it.

Many people with busy schedules bring packed lunches into work in glass containers. They’re easy to heat up in a microwave. But at one factory in New Taipei, one couple were horrified to see their lunchbox crack in two.

Mr. Tu
Scooter parts factory owner
When I reached in to take the box out, only half of it came out, with all the rice in it. We thought it was really dangerous. Thankfully nothing happened while it was in the microwave. But we didn’t dare eat the food. We were afraid there might be shards of glass in the rice.

If you take a good look at the broken box, you can see how clean the split is. The couple made do with the food they’d packed in a different box that day, and the next day, still rattled, they ordered a takeaway. They had no idea why the box had suddenly broken, after having microwaved it exactly the same way many times before.

Mr. Tu
Scooter parts factory owner
The way I put it in the microwave was just like I normally did. I just microwave it for a few minutes. We heat the vegetables separately so they were fine. It was just the rice that broke.

Lee Feng
Physics teacher
It might be that beforehand the box got knocked somewhere, causing it to have some small cracks in the glass. So then when they heated it in the microwave, because the rice inside got hot, and the glass was still cold, there was a heat differential between the rice and glass, causing them to expand unevenly, and finally making the glass split open at the spot where the cracks were.

For physics teacher Mr. Lee, the glass cracking is easy to explain. University aptitude tests have featured questions on the exact same phenomenon.

Lee Feng
Physics teacher
The question was, “There’s a glass, you fill it with very hot water, and it splits apart. What is the principle behind it?” The principle is this difference in temperature between the inside and outside, causing this uneven expansion of the inside and outside.

Mr. Lee suggests that before using any glass or ceramic container, you should first check the temperature range it is made to handle. And before you put it in the microwave, check to see there are no cracks. Even the smallest crack should stop you from putting it in the machine. Don’t put piping-hot food straight into a container, or wash utensils roughly. All of those high-risk activities could make your box the next to break in half.