Everybody who’s ever been in a classroom or at a science fair knows about the classic “make your own volcano” experiment. Over 99.99 percent of the time, it is a fun, hands-on way to teach kids about chemistry. However, with the wrong materials and too much vinegar, these volcanoes can become a badly painted time bomb.  

A teacher and 59 students have been injured at Holy Family High School in the south Indian city of Kochi after a volcano model exploded and sprayed a shower of shrapnel, according to a report published by The Times Of India. Two of the kids had to be rushed to the hospital with injuries to their arms and eyes, although thankfully their condition is stable.

Unless you slept through elementary school, you know that the experiment uses a chemical reaction between baking soda and vinegar to create a vinegary foam that flies out of the top of a bottle like lava flinging out of a volcano.

Four students presented their model volcanos outside in the schoolyard. It’s believed that one of the students placed pebbles and tile pieces within their model to give the volcano a bit more authenticity. While the exact cause of the explosion is not known, it’s thought that pressure built up within the mud-covered model. The explosion then caused the tile and pebble pieces to burst out like a nail bomb.

“It is suspected that the mud cover was thick and it put pressure on the plastic bottle containing vinegar and baking soda. This might have led to the explosion,” headmistress of the school Sr Sany Jose told The Times Of India.

“We are yet to identify what triggered the explosion. We have sent the material collected from the site for chemical analysis. We will know what triggered the explosion only after getting a chemical analysis report,” added local police spokesperson Sony Mathai.

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