Homemade bath bombs for kids
Making homemade bath bombs with kids is a fun activity to do together and also a fantastic STEM activity! They are straightforward to make and bring some good fun to bath time. They are also a great homemade present for friends and family.
How they work – A simple summary
Making bath bombs uses ingredients that are safe for children to handle but will sting if it gets in their eyes. Baking soda is a mild alkaline substance (base), and citric acid is a mild acid.
If the two are mixed together, nothing happens. However, when baking soda and citric acid are combined with water, a reaction occurs, resulting in gas and sodium citrate. The release of the gas, carbon dioxide(CO2), causes the bubbles to form. Once this reaction takes place, it cannot be reversed. The sodium citrate looks similar to baking soda, but it doesn’t react (bubble) when combined with an acid.
What you need – homemade bath bombs for kids
- Baking soda (bicarbonate of soda) (100g or 3.5oz)
- Citric acid (50g or 1.75oz)
- Cornflour /Cornstarch (25g or .87oz )
- Epsom salt (25g or .87oz) (optional- *if you don’t use Epsom salt, add an extra 25g of cornflour)
- Vegetable oil such as sunflower, coconut or olive oil (2 tbsp). For a harder version use rubbing alcohol (see below).
- Essential oil (ex. Lavender, rose, chamomile, orange (several drops to ¼ tsp)
- A few drops of liquid food colouring (not gel)
- Rose petals, lavender, grated orange peel or glitter (optional)
- Mixing bowl & small bowl
- Moulds (e.g. ice cube tray, silicone cupcake cases, baby food pots, plastic cookie cutters (placed on a tray), yoghurt pots, etc.)
To start, combine the baking soda, citric acid, corn flour and Epsom salts in a mixing bowl then stir or whisk it until all of the ingredients are evenly mixed.
In a small bowl mix together the vegetable oil, essential oil, and add 3-10 drops of food colouring (depending on how colourful you want them to be).
Next, slowly add the oil mixture into the large bowl of dry ingredients. Add it little by little and whisk/stir thoroughly between each addition.
Once all the oil is mixed in well, add a few drops of water and whisk it again (this will cause a little bit of fizzing, so do it quickly). The mixture should clump together and hold its shape without being very wet.
If you are adding petals, lavender, glitter, etc. put them on the bottom of the mould. Then place the bath bomb mixture on top and press it down. You may want to smooth it out with your finger or a spoon.
Leave the bath bomb to dry overnight. It can take longer to dry if it is in cold and damp surroundings, and less time if the air is dry and hot.
***Instead of using oil, you can also use rubbing alcohol to moisten the mixture. Rubbing alcohol makes the bath bombs harder and more robust. However, it dries fast so it may not give children enough time to put it in moulds before it hardens. Another excellent option is to split it (e.g. 1 tbsp oil and 1 tbsp rubbing alcohol) depending what ingredients you have available.
Questions to ask
- What happens when you mix the ingredients?
- What happens when you put the bath bomb in the water? What do you notice?
- Does this remind you of any other experiments you’ve done?
- How is this similar to baking soda and vinegar experiments? And different?
- Is there anything else you would like to try?
What they get from it – Homemade bath bombs for kids
Making homemade bath bombs with children is a great way to build upon other experiments with basic chemical reactions such as baking soda and vinegar. They can explore the similarities and differences between these reactions and then think about why certain ingredients are useful for a bath bomb and not for the others. Following recipes is an excellent way for children to practice reading for a purpose and to practice measuring. Research shows that people learn best (information is stored best in long-term memory) through hands-on, practical experiences (Hearns, Miller & Nelson, 2009; Hillman, 2011; Ferri, B.H., Ferri, A.A., Majerich, D.M., Madden, A.G., 2016).
This activity can also be a stimulus for further investigations and experiments, including ones inspired by children’s questions (see below – take it further).
Take it further
Children can try experimenting with different chemical reactions. They could investigate the difference in responses when mixing vinegar, citric acid, kool-aid, lemon juice, etc. with baking soda. Children could also try adding different types of soap to see how that changes the reaction.
You may also want to see my posts such as Baking Soda and Vinegar Painting Experiment for Kids (coming soon), Explosive Baking Soda and Vinegar Experiment for Kids, Color pH Baking Soda and Vinegar Science Experiment, Bicarbonate of Soda and Vinegar Experiment and Turmeric pH Indicator Experiment.
Ferri, B.H., Ferri, A.A., Majerich, D.M., Madden, A.G. (2016). Effects of In-Class Hands-On Laboratories in a Large Enrollment, Multiple Section Blended Linear Circuits Course. Advances in Engineering Education, 5 (3). https://files.eric.ed.gov/fulltext/EJ1121997.pdf
Hearns, M.K., Miller, B.K. and Nelson, D.L. (2009). Hands-On Learning versus Learning by Demonstration at Three Recall Points in University Students. OTJR: Occupation, Participation and Health, 30 (4), 169-171. https://journals.sagepub.com/doi/10.3928/15394492-20090825-01
Hillman, C.N. (2011). The effects of hands-on learning versus learning by demonstration on memory in community dwelling older adults (Doctoral dissertation, The University of Toledo). Retrieved from https://pdfs.semanticscholar.org/6231/d55fc1c730ec086f012677c54141f466e18e.pdf