Homemade fizzy bath bombs are a simple science project that results in fun bath treats you can use or give as gifts. The recipe is easy enough that kids can help, plus you can teach (or learn) about acid-base reactions.
Fizzy Bath Bomb Ingredients
There are as many different recipes for homemade bath bombs as there are people who make them, so feel free to adjust ingredients to suit your needs. The key ingredients you need for the fizzing action are an acid (usually citric acid) and a base (usually baking soda or sodium bicarbonate), plus an oil to help hold the active ingredients together. It’s up to you whether to add Epsom salts or sea salt, which are a nice addition to the bath and add sparkle, corn starch, which helps the shape stick together more smoothly and makes the bath water feel silky, scented oils, food coloring, glitter, or dried flowers. Experiment and have fun!
For 6-10 bath bombs (depending on size) you need:
- 1 1⁄2 cups baking soda (sodium bicarbonate
- 1⁄2 cup citric acid powder (usually sold with home canning supplies)
- 2 teaspoons oil (good choices are coconut oil, sweet almond oil, jojoba oil, or olive oil)
Consider adding any or all of the following:
- corn starch (cut baking soda down to 3/4 cup and add 3/4 cup corn starch)
- few drops essential oil (e.g., lavender, chamomile)
- dried flowers or herbs (e.g., lavender, rose petals, rosemary)
- 1/2 cup Epsom salt
- or 1/2 cup sea salt
- 1/2 teaspoon to 1 teaspoon of borax (natural disinfectant)
Assemble the Fizzy Bath Bombs
- In separate bowls, mix the dry ingredients and the liquid ingredients.
- Add liquid ingredients a bit at a time to the dry ingredients to get a shape you can mold.
- You can press the mixture into candy molds or roll it out to cut with small cookie cutters. Another option is to shake the ingredients into a plastic bag and use as fizzy bath salts. If you do this, I recommend adding Epsom salts, because they are pretty and therapeutic.
- Let the bath bombs dry at least a day so they won’t fall apart.
- Wrap the bath bombs in plastic wrap to seal them from air. Humidity in air will ruin your bath bombs, which is why bath bombs lose their power over time.
- Spray candy molds or cookie cutters with non-stick cooking spray or coat them with your oil of choice before adding the mixture, to keep the bath bomb from sticking.
- Dissolve bath bombs in warm or hot water rather than cold water for the best fizzing action.
- Consider using flower petals for color and omitting food coloring. Food coloring has a tendency to fade, plus it adds water to the mixture, which reacts a bit of your baking soda and acid mixture. A few drops won’t hurt anything, but don’t get carried away with this ingredient.
How Fizzy Bath Bombs Work
When you drop a bath bomb in water, the baking soda (base) and citric acid (acid) react to form carbon dioxide. The carbon dioxide molecules stick together to form bubbles.