How to Make Bath Bombs: Easy DIY Recipe

Drop a homemade bath bomb into warm water and something almost magical happens. It fizzes, spins, and releases a cloud of colour and scent. An ordinary soak becomes a little ceremony. Here’s the best part: you can make a batch in your kitchen this afternoon for a fraction of what the shops charge.

Bath bombs are one of my favourite beginner workshops because the whole thing is forgiving, fast, and endlessly tweakable. A handful of cheap ingredients, a mixing bowl, twenty minutes. That’s it. Baking soda and citric acid react the moment they meet water, and the fizz you see is just that reaction happening in your tub instead of your mixing bowl. Master that, and you’ll never buy a bath bomb again.

Materials List

• Bicarbonate of soda (baking soda) — 200g. The base of every bomb. Cheap, and you probably have it already.
• Citric acid — 100g. This is the fizz-maker. Buy it as a powder online or from the home-brew aisle. Alternative: cream of tartar works in a pinch, though the fizz is gentler and the texture slightly softer.
• Cornflour (cornstarch) — 50g. Keeps things smooth and stops the mix being too crumbly. Alternative: arrowroot powder behaves almost identically.
• Epsom salts — 50g. Lovely for sore muscles. Alternative: fine sea salt, but skip it entirely if you have sensitive skin.
• Essential oils — around 10–15 drops total. Lavender for calm, peppermint for zing, orange for cheer. Alternative: fragrance oils designed for cosmetics, which hold their scent longer.
• Witch hazel — in a spray bottle. This is your binder. Alternative: water in a spray bottle, but witch hazel dries faster and reacts less with the powders.
• Food colouring or mica powder — a few drops. Mica gives richer colour; liquid food colouring is fine but use it sparingly. Alternative: a pinch of beetroot powder or spirulina for a natural tint.
• Polysorbate 80 — optional, 1 teaspoon. It helps colour and oil disperse in water instead of leaving a ring on the tub. Skip it if you don’t mind a quick rinse afterwards.
• Moulds — two-part metal bath bomb moulds are ideal. Alternative: silicone cupcake trays, ice cube trays, or even clean plastic baubles from a craft shop.

Step-by-Step

1. Weigh everything first. Get your bicarb, citric acid, cornflour, and salts into separate bowls before you start mixing. This recipe moves fast once the wet ingredients appear, and stopping to weigh mid-mix is how batches go wrong.
2. Sift the dry ingredients together. Tip the bicarb, citric acid, cornflour, and Epsom salts into a large bowl, then push them through a fine sieve. This takes an extra minute but removes every lump. Clumpy powder means crumbly bombs — trust me on this one.
3. Whisk thoroughly. Use a balloon whisk for a full thirty seconds until the mixture looks like soft, uniform snow. Any streaks of citric acid left unmixed will fizz in the wrong place later.
4. Add your colour. If you’re using mica, stir it in dry now. If you’re using liquid colouring, hold off — it goes in with the wet ingredients. Add a little at a time; you can always deepen the shade but you can’t take it back.
5. Combine the wet ingredients in a small cup. Measure your essential oils, add the polysorbate 80 if you’re using it, and stir. If you’re using liquid colouring, add a drop or two here as well.
6. Spritz, don’t pour. This is the single most important step. Spray your witch hazel over the dry mix two or three times, then whisk immediately. Repeat, spraying and whisking, until the mixture just holds together when you squeeze a handful. It should feel like slightly damp sand, not wet dough.
7. Add the oil mixture. Drizzle it in slowly while whisking, then spritz once more if the mix needs it. Stop the moment it clumps. If you hear or see fizzing, you’ve added too much liquid — work faster and add no more.
8. Test the squeeze. Grab a fistful and press. It should hold its shape when you open your hand, then crumble when you poke it. That’s your target texture. Too dry and it won’t hold; too wet and it will puff up and crack as it dries.
9. Pack your moulds firmly. Overfill each half of the mould, press the two halves together, and twist gently. Give it a firm squeeze to compact the mixture, then tap the outside. Don’t twist too hard — the seam is where most bombs break.
10. Unmould carefully. Wait a minute, then tap the mould and lift one half away. If the bomb sticks, leave it another minute. If it crumbles, the mix was too dry — return it to the bowl with a single extra spritz.
11. Dry for 24 hours. Set your bombs on baking parchment in a cool, dry room, away from radiators and windows. Humidity is the enemy here. After a full day they’ll feel hard and sound hollow when tapped.
12. Store properly. Wrap each bomb in cling film, or seal them in an airtight jar with a sachet of silica gel. Kept dry, they’ll stay fizzy for months.

Beginner Tips

Let’s talk about the mistakes I see in every single workshop, so you can skip straight past them.

Don’t add water straight from a jug. Ever. A tablespoon of water poured in will activate your citric acid on the spot and your batch will fizz in the bowl. Always spritz. If you must use water, use a spray bottle set to the finest mist you own.

Don’t skip the sieving. It feels fussy. It isn’t. Lumpy citric acid creates pockets of fizz that break bombs apart from the inside.

Don’t over-wet the mix. Slightly too dry is always better than slightly too wet. A dry mix can be rescued with another spritz. A wet mix is already fizzing and there’s no going back.

Don’t unmould too early. Give it a full minute. Patience here saves you from a bowl of crumbs.

And here’s a counter-intuitive one: don’t aim for a perfectly smooth, shiny, shop-bought-looking bomb on your first go. Slightly rustic bombs with a bit of texture work just as well in the tub. Chasing perfection is what makes beginners over-handle the mix, and over-handling is what breaks it. Rough edges are fine.

Creative Variation

Once you’ve nailed the basic recipe, the fun part begins: layering colours. Split your dry mix into two or three bowls before you add any wet ingredients. Colour each bowl separately, bind each one, then pack your mould with alternating spoonfuls — a scoop of lavender, a scoop of pink, a scoop of yellow. Press gently between layers so they hold together, but don’t stir. When the bomb hits the water, the colours unfurl in ribbons.

You can also hide a tiny surprise inside: a few dried flower petals, a small toy for the kids, or a pinch of extra-fine glitter (biodegradable, please). Just pop it in the centre when you’re halfway through packing the mould.

Troubleshooting

My mix started fizzing in the bowl. Too much liquid, too fast. Work quickly — pack it into moulds immediately, even if it’s already reacting. The bombs will be less fizzy in the tub but still usable. Next time, spritz less and whisk more.

My bombs crumble when I unmould them. The mix was too dry. Tip it back into the bowl, add one spritz of witch hazel, whisk, and try again. Also check you’re packing firmly — loose packing is the other common culprit.

My bombs are cracking on top. Classic sign of too much moisture. They’ll still work, but they’ll look a bit rough. Leave them to dry longer and reduce your liquid next batch.

My bombs puffed up and split at the seam. Overfilled moulds. Use slightly less mixture per half and press the halves together more firmly.

They’re not fizzing much in the bath. Either your citric acid is old, or you lost too much fizz during making. Buy fresh citric acid — it does degrade over time — and be stingier with the witch hazel.

The colour stained my tub. That’s a liquid food colouring problem. Switch to mica powder, or add a teaspoon of polysorbate 80 to your wet ingredients next time.

They’ve gone soft in storage. Moisture got in. Wrap them individually and store them somewhere genuinely dry. A bathroom cupboard is the worst possible place for them, however tempting it is.

Making bath bombs is one of those rare crafts where the ingredients cost pennies, the learning curve is gentle, and the results feel genuinely luxurious. Your first batch might be a little lumpy. Your second will be better. By your third, you’ll be handing them out to friends and pretending it was harder than it was. Grab your bicarb, clear a corner of the kitchen, and give it a go this weekend — your bath is waiting.