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How do bath bombs work? © Getty Images

How do bath bombs work?

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Bath bombs are made of quite simple ingredients that combine in water to make a fizzy bath time experience.

Asked by: John Mitchell, Glasgow

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The part that makes them fizz is the same as an Alka Seltzer or soluble aspirin tablet: sodium bicarbonate and citric acid. These chemicals are inert when they are dry powders, but in water they dissolve and the citric acid reacts with the sodium bicarbonate to form sodium citrate and carbon dioxide.

The sodium citrate stays in solution and you don’t really notice it, but the carbon dioxide bubbles out as a gas that helps the bath bomb break up. This lets the detergents, perfumes and oils that make up the rest of the bath bomb mix with the bathwater.

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Authors

luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.

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