Bath bomb

Bath bombs are hard-packed mixture of dry ingredients which effervesces when wet. They are used to add essential oils, scent and colour to bathwater. They are a form of bath fizzies.

LUSH brand bath bombs on display in a shop.

Composition

Bath bombs' primary ingredients are a weak acid and a bicarbonate base. These are unreactive when dry, but react vigorously when dissolved in water to produce their characteristic fizzing over a period of several minutes; carbon dioxide bubbles on bathers' skin gives a tickling sensation some find pleasant. A common chemical mixture is citric acid and sodium bicarbonate:

C₅H₇O₅COOH + NaHCO₃ → C₅H₇O₅COO⁻Na⁺ + H₂O + CO₂

The other ingredients in bath bombs can vary considerably. Most have scented ingredients — such as essential oils — in their composition to impart a pleasant fragrance to the water, and some are brightly coloured. Solid objects, such as glitter, can be added. In Japan, there are usually bath balls, often called Bikkuri Tamago (びっくりたまご lit. "Surprise Egg"). When a Japanese bath ball is fully dissolved, a small object, usually a figure, is revealed. There are many anime-themed bath balls in Japan. In America, there are ring bath bombs, often called Pearl Bath Bombs. When a Pearl Bath Bomb is fully dissolved, a small pink pearl is revealed with a ring inside.

Production

Bath bombs are generally spherical but can be found in a variety of shapes, such as tablets or lumps. Shops offer a wide range of bombs, but they can also be made at home.