You will need:
- A Mould or small container (plastic medicine cups are great!)
- A bowl
- Paper towel (or cleaning cloth)
- Stirring stick
- Food colouring
- Bicarb soda
- Citric Acid
- Corn Flour
- Fragrance (kid safe oils and potpourri leaves)
Step 1: Mix 1 cup of bicarb soda with 1/3 cup of citric acid, 1/3 cup of corn flour and a sprinkle of potpourri leaves and then stir well.
Step 2: In a small bowl, combine 2-3 drops of kid safe perfumed oils or your choice, 1/2 teaspoon of water and 3-4 drops of food colouring. Place this solution into the first mixture and stir quickly with a stirring stick. If it starts to foam, stir quicker!
Step 3: Using disposable gloves, continue to combine the ingredients with your fingertips until it starts to clump together when compressed in your hand. Do this with your fingers, not a spoon, so the liquid is distributed evenly. The mix is now ready to go into a mould.
Step 4: Pack the mixture firmly into a mould and leave it to set overnight! To get your bath bomb out of the mould, tap it gently on each side and ease it out. You can make as many as you like!
STOP & THINK
When you combined the liquid ingredients with the solid ingredients it was important to stir very quickly so the bulk of the liquid doesn’t sit in one spot for too long? Why is this so and why does the bath bomb fizz when it is dropped into the bath?
There are two active ingredients in the bath bombs that react with each other in the presence of water. Bicarb soda is a base and Citric Acid is an acid. When they react, we get a neutralisation reaction which produces Carbon Dioxide (CO2) as a by-product. That’s why your bath bombs fizz so well under water.
Note: This is a Street Science Original Activity and may be used only in publications with written permission of the Street Science Executive. For non-profit use only.