Science, Tech, Math › Science How to Make Fizzy Bath Bombs Share Flipboard Email Print altrendo images / Getty Images Science Chemistry Projects & Experiments Basics Chemical Laws Molecules Periodic Table Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated November 16, 2019 Use your chemistry skills to make a fizzy, scented bath bomb (bath ball). Make them for yourself or give them as gifts. It's pretty easy to make and takes only about 15 minutes. Fizzy Bath Bomb Chemistry Fizzy bath bombs or bath seltzers are an example of an acid-base reaction. The citric acid (weak acid) and baking soda (sodium bicarbonate, a weak base) react together to release carbon dioxide gas. This gas forms the bubbles. The citric acid and baking soda don't react until they are in an aqueous (water-based) solution. The cornstarch helps keep the bath bombs dry until you add them to the bath. You could substitute Epsom salts in place of the cornstarch if you prefer. What You Need for Bath Bombs 2 tablespoons citric acid2 tablespoons cornstarch1/4 cup baking soda1/4 teaspoon fragrance oil3 to 6 drops of food color3 tablespoons vegetable oil How to Make a Bath Bomb Mix all dry ingredients (citric acid, cornstarch, baking soda) in a bowl.In a different bowl or a small cup, mix the vegetable oil, fragrance, and coloring together.Slowly incorporate the oil mixture into the dry ingredients. Mix well.Roll clumps of the mixture into 1-inch balls and put them on waxed paper. They will be semi-hard within two to three hours, but allow 24 to 48 hours for them to fully dry before storing them.Store bath balls in a sealed container, away from moisture.Add a few to the bath and enjoy! For gift-giving, the balls may be placed in individual candy cups. Useful Tips Fragrance and/or coloring is optional.Suggested vegetable oils include coconut oil, avocado oil, apricot kernel oil, sweet almond oil, or olive oil, although any emollient oil will work.Use small molds to make three-dimensional fizzy bath shapes.