Bath bombs fizz because of a reaction between an acid and a base. The acid is usually citric acid and the base is usually sodium bicarbonate (baking soda). When these two ingredients mix with water, they create carbon dioxide gas, which causes the fizzing effect.
This is like other fizzing products such as denture cleaner tablets and flavored tablets added to water to make a fizzy drink.
So, what is sodium bicarbonate?
Sodium bicarbonate (baking soda) is a white, crystalline powder that is commonly used as a leavening agent in baking and for cleaning. It can be produced by combining sodium carbonate (also known as washing soda) with carbon dioxide, or by mining it from natural deposits. The chemical formula for sodium bicarbonate is NaHCO3.
What is citric acid and how is it made?
Citric acid is a weak organic acid commonly used as a food preservative and flavor enhancer. It is found naturally in citrus fruits, especially lemons and limes, but it can also be produced commercially through the fermentation of sugar (glucose or sucrose). This process is called citric acid fermentation. It is used extensively in food and beverage products.
As a bath bomb maker your two main ingredients will be baking soda and citric acid. In fact, most bath bomb recipes use between 2 and 3 times more baking soda than citric acid. The other ingredients you will use include water, oil, fragrance and color. These will be in quite small amounts in comparison to the dry powders of baking soda and citric acid.
However, there are many types of bath bomb recipes. For example, some recipes use palm fat (a solid at room temperature) and cocoa butter (also a solid at room temperature) that create a rich moisturizing effect in the bath. These butters are evenly blended with the sodium bicarbonate and citric acid to create an amazing bath bomb experience. We have a recipe for this type of bath bomb in our Business Guide, which comes with each B-3 we sell.
When the bath bomb ingredients are mixed, the combined mixture will have the consistency of barely damp sand. It will clump slightly when squeezed in the hand. This is when it is pressed into a mold under force using a B-3 Bomber or a B-49 multi bath bomb press.