The Science of Bath Bombs and Shower Steamers

All my bath bombs and shower steamers have three key ingredients; Sodium bicarbonate (baking soda), citric acid, and witch hazel. To this, I add essential oils, natural fragrances, mica, and/or botanicals, and other additives. To make bath bombs or shower steamers I will mix the dry ingredients, then my essential or natural fragrance oil, and then I will add witch hazel until the mixture is thick and puddy like. Then the mix will be pressed into molds and left to dry for about two days.

Sodium Bicarbonate (NaHCO3)

Sodium bicarbonate (Sodium bicarb/Baking soda) is a mineral found dissolved in many mineral springs. It spontaneously reacts with acids to produce CO2. Even though it can react with bases as well as acids, it can not neutralize bases like it can acids.

Citric Acid (C6H8O7)

Citric acid is found in nearly every fruit and juice available. It is commonly used as a natural preservative and has a PH of between 3 and 6. Citric acid and baking soda react when in contact with water. The reaction produces sodium citrate, carbon dioxide gas, and water

NaHCO3 + C6H807 + H20 -> Na3C6H5O7 + H20 + CO2

Witch Hazel

Witch hazel as we know it today is a distilled liquid that is made from the leaves and bark of a witch hazel plant. It is commonly used as a less irritating and more natural alternative to rubbing alcohol. This is because the witch hazel itself already has a 14 percent alcohol content. When mixing the baking soda and citric acid, you obviously don't want to use water because that would trigger the chemical reaction, but you also don't want to use straight alcohol because it is very drying, irritating, and isn't the most natural thing you can use. As a result of this, many people opt to use witch hazel to dampen their mixture. While witch hazel can trigger the reaction between baking soda and citric acid if you use too much at one time, as long as it is used sparingly it will not trigger the reaction.