What Ingredients Do You Need to Make a Bath Bomb?
Every bath bomb starts with the same two non-negotiable ingredients: baking soda (sodium bicarbonate) and citric acid. These are what create the fizz. When they hit water, they trigger a carbon dioxide reaction that produces the effervescence people love. The standard ratio is 2 parts baking soda to 1 part citric acid by weight. From there, the remaining ingredients add moisture, structure, scent, and color:
- Baking soda — the alkaline base; makes up roughly 40-50% of your recipe
- Citric acid — reacts with baking soda to produce fizz; use at half the amount of baking soda by weight
- Carrier oil — sweet almond, coconut, and sunflower all work well; use at 5-10% for skin feel and binding
- Witch hazel or isopropyl alcohol — brings the dry mix to a damp-sand consistency without triggering the fizz reaction early
- Cornstarch — slows the fizzing reaction for a more even dissolve; adds a silkier feel in the water
- Epsom salt — mild skin-softening effect; adds hardness to the finished bomb
- Fragrance or essential oils — add scent at 1-3% of total recipe weight, but always verify with the fragrance calculator to be sure.
- Cosmetic-grade colorants — micas, lakes, or bath-safe dyes
- Polysorbate 80 (optional) — emulsifier at 1-2% that disperses oils into the bathwater and prevents a greasy tub ring
If you're selling or gifting your bombs, that last ingredient is worth including. It helps to prevent oils from floating on the surface of the bath water.
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