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Supported by Rolls-Royce

Butcher, baker, bath bomb maker

Look into the chemistry of clean and make some brilliant bath bombs from bicarb.
Plan a session with this activity

You will need

  • Ingredients (see recipe card)
  • Access to water
  • Kitchen scales
  • Mixing bowls
  • Cups or beakers
  • Whisks
  • Measuring spoons
  • Bath bomb moulds like empty yoghurt pots, ice cube trays or leftover Easter egg packaging
Recipe card (Brilliant bath bombs)
PDF – 229.2KB

Before you begin

  • You could run this activity as one of two or more bases. This allows everyone to work together and save resources. If you’re doing more than one experiment, make sure you have enough adult supervision for each one and that all the necessary equipment is ready.
  • Bath bombs need time to dry before they can be tested. The group could prepare their own in one session and take them home to try out themselves. You could prepare some beforehand to show them what’ll happen and explain the science while they’re waiting for theirs to dry.
  • Double-check to see whether anyone has an allergy or sensitivity to any of the ingredients.
  • Let everyone know about this activity beforehand and encourage everyone to bring something along that they can use for a mould. Silicon trays or cupcake cases work well, as do yoghurt pots or plastic biscuit cutters. Bring some along for those who can’t find anything.

Make your bath bombs

  1. Everyone should split into pairs or small groups. Give each group a ‘Recipe card (Brilliant bath bombs)’ and all the ingredients and equipment they’ll need.
  2. There are instructions to tick off on the recipe card. Start by weighing out and adding the bicarbonate of soda, citric acid, corn flour and Epsom salt to a mixing bowl. Whisk the ingredients together.
  3. Use teaspoons and tablespoons to measure out the correct quantities of oil, essential oil and food colouring in a cup or beaker. Mix these together too.
  4. Slowly add the oil mixture to the dry ingredients bowl. Do this a little bit at a time and keep mixing.
  5. When all of the oil has been added, add a few drops of water so that the mix clumps together and keeps its shape when pressed.
  1. Take the mould and add any decorations to the bottom of it. Pack the mixture from the bowl on top and press it down into the mould. Smooth the top with a teaspoon.
  2. Put the filled mould somewhere it can dry for the next couple of hours (or pack them up to take home).
  3. While waiting for bath bombs to set, everyone should come together and discuss the science of bath bomb reactions. Everyone will need a bath bomb to test. They can either use their own if you made them in a previous session, or a pre-prepared example.
  4. Fill a sink or bowl with water and take turns dropping in bath bombs. See if anyone knows why the bath bomb reaction takes place.
  1.  Everyone should say what they can see, hear and smell while the bath bomb reacts.


Everyone worked together to craft their individual bath bombs. All of them probably turned out slightly different, as groups will have followed the recipe in their own way and used different decorations, oils and food colourings. Was it easier to make the bath bomb working together with others? Which parts might’ve been tough to do alone?


All activities must be safely managed. Use the safety checklist to help you plan and risk assess your activity. Do a risk assessment and take appropriate steps to reduce risk. Always get approval for the activity and have suitable supervision and an InTouch process.


Supervise young people, and only do science activities that are advised and age appropriate for your section. Test activities first, to make sure you’re confident you can lead them safely. Use protective clothing where necessary.


Check for allergies before you begin and read the guidance on food safety. Make sure you have suitable areas for storing and preparing food and avoid cross contamination of different foods.