What is a bath bomb?
A bath bomb is made of a dry, compressed, combination of ingredients that fizz and bubble when they touch water. A simple one contains, more often than not, baking soda, corn starch, citric acid, and water as a binder. While this will give you the expected fizz, it won’t provide you with any scents, colors, or added moisturizing benefits which most people enjoy.
Therefore most companies that sell them, such as Lush or Bath and Body Works (and your home DIYer) add additional ingredients. These include essential oils for scents, coconut oil, almond oil, epsom salt to moisturize the skin. Additionally, they will add dyes and other additives such as glitter or dried flowers which get mixed into or float in a bath.
Can Bath Bombs Expire?
As with food products, bath bombs too have ingredients with an expiration date and a recommended shelf life. The shelf life of bath bombs refers to how long you can store them, and they still maintain full effectiveness. A bath bomb has an average shelf life of about six months.
Common bath bomb ingredients include citric acid and sodium bicarbonate (baking soda). While baking soda and citric acid both have long shelf lives, citric acid starts losing its potency as time passes. However, you can easily preserve the potency of the citric acid by storing it in a tightly sealed container.
When they are exposed to water or moisture, bath bombs tend to create an acid-base reaction. If they are exposed too much to the moisture in the air, they might not fizz anymore and would begin to lose their effective properties.
The fresher your bath bomb is, the faster they fizz, and the better they work. You can utilize tight bulk bath bomb containers to store your fizzies for a long time, and they'll still be usable, but they cannot work effectively as compared to fresh ones.
You should store bath bombs in a cool and dry place such as basements or cupboards. If you like in a humid environment, you can ensure your bath bombs are properly stored with a dehumidifier.
How Does it Work?
The “bomb” aspect of a bath bomb is the fizziness. But what’s going on in those spheres that make them so fizzy? Two of the key ingredients to a bath bomb are citric acid and sodium bicarbonate. You might also know sodium bicarbonate by its more common name, baking soda. These two ingredients are what cause the impressive and delightful fizz when the bath bomb enters the water.
When sodium bicarbonate (NaHCO3) comes in contact with water, the sodium (Na) molecules break off from the bicarbonate (HCO3). At the same time, the citric acid is dissolving, with a single hydrogen ion (H+) separating from the rest of the molecule. When the released hydrogen ion from the citric acid encounters the bicarbonate from the baking soda another reaction happens! This time, carbon dioxide (CO2) gas is released as one of the end products. The carbon dioxide forms bubbles in the soap and bath water, and rushes to the surface with a delightful fizz.