Bath Bomb Recipe: A 200 g Batch (About 4 Bombs)
A bath bomb is baking soda and citric acid held in a shape. When they meet water, they fizz. The craft is keeping them from meeting until the bath. That means dry ingredients, a thin stream of liquid, firm packing and a dry day. This is the Classic Fizzy Bath Bomb formula, written for a 200 g batch that makes about four bombs of 50 g.
The formula (200 g, about 45 minutes)
| Phase | Ingredient | INCI | % | 200 g batch |
|---|---|---|---|---|
| A (dry) | Baking soda | Sodium Bicarbonate | 48 | 96 g |
| A (dry) | Citric acid | Citric Acid | 24 | 48 g |
| A (dry) | Cornstarch | Zea Mays Starch | 12 | 24 g |
| A (dry) | Epsom salt | Magnesium Sulfate | 8 | 16 g |
| B (liquid) | Sweet almond oil | Prunus Amygdalus Dulcis Oil | 4 | 8 g |
| B (liquid) | Polysorbate 80 | Polysorbate 80 | 3 | 6 g |
| B (liquid) | Sweet orange essential oil (optional) | Citrus Sinensis Peel Oil | 1 | 2 g |
| Total | 100 | 200 g |
If you skip the essential oil, add its 2 g to the cornstarch to keep the total at 100 %. You also need bath bomb moulds, a whisk, a sifter and a rack.
Method
- Sift all the dry ingredients together twice to remove lumps.
- Whisk the almond oil, polysorbate 80 and optional essential oil together in a separate bowl.
- Pour the liquid into the dry mix in a thin stream while whisking fast so it does not fizz.
- Pack the mix firmly into the mould halves, press them together and unmould after 2 hours.
- Dry on a rack for 24 hours, then store in a dry, airtight container or shrink wrap.
Why each ingredient is there
- Baking soda and citric acid are the fizz. Together they make up 72 % of the formula.
- Cornstarch is a filler that softens the feel of the water.
- Epsom salt is a mineral salt. Swap it for extra cornstarch if you want a smoother pack.
- Almond oil is the emollient. Sunflower or jojoba oil also work.
- Polysorbate 80 is a solubiliser, which spreads the oil through the bathwater instead of leaving a ring.
Troubleshooting
| Problem | Likely cause | What to try |
|---|---|---|
| Crumbles | Mix too dry | Add one or two sprays of witch hazel and re-test a small handful |
| Fizzes during mixing | Liquid added too fast | Use a thin stream and whisk fast |
| Soft after storage | Humidity | Wrap or seal them in an airtight container |
How long do bath bombs last?
The planned shelf life is 3 to 6 months, kept dry. Humidity is the enemy. Citric acid and baking soda react with any moisture in the air, so an open dish in the bathroom shortens their life quickly.
Safety
- Oils make the tub or shower floor slippery. Use a non-slip mat, wipe the tub after use and step out carefully.
- The formulary's guideline for bath bombs is 1 to 2 % total essential oil. Skip citrus oils for children.
- Avoid essential oils in products for babies and children, and when pregnant or nursing unless a qualified professional advises otherwise.
- Patch test the mix on your inner forearm for 24 hours, and stop if irritation appears.
Maximums for each product type are in the essential oil dilution chart.
Make a set
A box of bath bombs and a sugar scrub makes a ready gift. The sugar scrub recipe is a good partner, and homemade spa gifts has packaging ideas. For how long other kinds of product last, see how long homemade skincare lasts.
More in the book
The Natural Skincare Formulary includes this formula and a Cocoa Butter Bath Bomb, plus formulas for bath salts, bath melts, a chamomile and lavender bath tea and eucalyptus shower steamers. A bonus booklet lays out four themed spa nights with menus and timings.
