How To Make Bath Bombs Safely

Jessica Clifton

by Jessica Clifton

22nd July 2020

A warm, soothing, soapy bath after a long day at work is the ultimate in relaxation…and maybe more so if you know that you’re enjoying it with a bath bomb you’ve made.

Making your own bath bombs is fun, and can save you money – plus, you’ll get the exact scent you want. However, it’s important to make your own bath bombs safely and we explain how to do just that. 

How do bath bombs work?

The fizz or gas that is generated by bath bombs when they’re mixed with water is actually just carbon dioxide, the same gas you’ll find in soft drinks and champagne, and the same gas that we exhale. The fizz that bath bombs create when they’re mixed with water is the product of a chemical reaction.

Although there are several ingredients in bath bombs such as colour, bath salts and scents, bath bombs only have two main active ingredients that are responsible for the fizz. These active ingredients are baking soda (sodium bicarbonate) and citric acid, a basic substance and an acidic substance.

The chemical reaction in bath bombs is between citric acid and sodium carbonate, and the fizz is carbon dioxide

The chemical reaction in bath bombs is between citric acid and sodium carbonate, and the fizz is carbon dioxide

The two active ingredients are in solid (powder) form and are held together by an inert binder, usually corn starch. Once a bath bomb is put in water, the sodium bicarbonate and citric acid dissolve and react.

Many bath bombs also contain ingredients that are meant to improve the health of the skin such as milk or fruit extracts. As you’re making your own bath bombs, you can add other ingredients you love the smell of and completely personalise them to suit you. 

How do I make my own bath bombs safely?

Making bath bombs is relatively easy and safe. Their main ingredients, namely, baking soda and citric acid, are edible. You can use food colours as pigments, and bath bombs typically only take about 10 minutes to make (although you’ll need several hours of drying time).

Bath bomb ingredients

  • 1 cup of baking powder
  • 3 teaspoons of essential oil
  • 2 teaspoons of olive or almond oil
  • Food colouring of your choice
  • ½ cup of citric acid

Oil is used in bath bombs to combine the two active ingredients, which are both powders

Equipment you’ll need to make your own bath bombs

  • 2 glass or metal mixing bowls
  • A whisk
  • A pair of rubber gloves
  • A sieve
  • A bottle with a spray nozzle
  • Bath bomb moulds*

*If you don’t have moulds specifically for bath bombs, you can use other types of moulds such as chocolate moulds, bauble moulds, shot glasses, ice cube trays, muffin trays, etc.

Step-by-step instructions for making bath bombs

  • Step 1: Wear gloves and sieve the citric acid and baking powder into a mixing bowl. Whisk the two powders together.
  • Step 2: Use a separate mixing bowl to combine the liquid ingredients. Thoroughly mix the essential oil, olive oil or almond oil and the food colouring.
  • Step 3: Carefully add the liquid mixture to the powder mixture. To avoid clumping, stir the mixture at regular intervals.
  • Step 4: Once all the ingredients are thoroughly mixed, pack handfuls of the mixture into the moulds. At this stage, the bath bombs may crumble because they’re very dry. If that happens, spray a small amount of water onto the bath bombs while they’re in the moulds.
  • Step 5: When the bath bombs have taken the shape of the moulds, carefully remove them and let them dry under direct sunlight. It may take several hours before they are completely set.
You can use all kinds of different ingredients in bath bombs and make them to suit you

You can use all kinds of different ingredients in bath bombs and make them to suit you

The bath bomb chemical equation

Once the bath bombs dissolve in water, their active ingredients become aqueous solutions. The alkaline and acidic substances react. The chemical reaction in the water is summarised in this balanced chemical reaction equation:

3NaHCO3 + C6H8O7 🡺 3Na+ + (C6H5O7) 3- + 3H2O + 3CO2

Among the by-products are the ions of sodium and citric acid, which become sodium citrate (Na3HCO3) when the solution is dried. Water and carbon dioxide are also produced in the reaction process. The carbon dioxide is released as bubbles in the water.

What’s the chemical reaction in bath bombs?

The chemical reaction in bath bombs is between an acidic substance and an alkaline or basic substance – citric acid and sodium carbonate, respectively. An acid-base reaction is also called a neutralisation reaction.

This type of reaction usually produces salts and liberates gases. They are often exothermic reactions, or reactions that produce heat. In this case, however, the reaction is endothermic. The heat or thermal energy from the environment is absorbed.

Are bath bombs safe to use?

Bath bombs might be even safer than detergents, soaps, and shampoos because they contain edible ingredients. Even the acid ingredient, citric acid, is an edible acid present in citrus fruits. This acid is also used as a preservative. Of course, food colouring, baking powder, and cornstarch are all common food ingredients.

However, not all bath bombs meet the same quality and safety standards. It all depends on the added ingredients. Generally, most commercially available bath bombs have edible and non-toxic added ingredients like vitamin D, oatmeal, milk, and honey. The main danger is the possibility of an allergic reaction, so it’s crucial that you check the label if you’re purchasing a bath bomb. Of course, it might be safer to make your own!


All content published on the blog is for information only. The blog, its authors, and affiliates cannot be held responsible for any accident, injury or damage caused in part or directly from using the information provided. Additionally, we do not recommend using any chemical without reading the Material Safety Data Sheet (MSDS), which can be obtained from the manufacturer. You should also follow any safety advice and precautions listed on the product label. If you have health and safety related questions, visit