Citric acid with sodium bicarbonate form the basis of our explosive bath bombs. When added to the water, this creates carbon dioxide and causes a bubbling, fizzing action. Many colours, fragrances, essential oils, flowers and herbs can be added to make uniquely fragrant ballistics. As they break down in the water, the effect of the essential oils is heightened.
Alchemists were aware of the acid as early as 700AD. It was first isolated in 1784 (from crystallised lemon juice) by a Swedish chemist, Carl Wilhelm Scheele. Citric acid is a naturally occurring fruit acid. In lemons and limes, it can account for up to 8% of the dry weight and has a very acidic taste.
Lush buys citric acid from European suppliers, who produce it from non-genetically modified vegetables and the molasses extracted from them. The molasses are crushed, mixed with lime and stacked in trays; the mix is then sprayed with a natural mould spore, allowing the fermenting mix to turn grey and fuzzy, becoming citric acid.
The mould used is called Aspergillus Niger, and is not present in the finished raw citric acid, thanks to an active carbon treatment and crystallisation, which are part of the highly controlled manufacturing process.