How to Make Bath Bombs (Instructable that was moved)
As I’ve noted before, Instructables has changed their business model, reducing access to content to non-paid visitors. Since all of my work was published under a Creative Commons non-commercial license, I’ve removed it from Instructables and am republishing it here, so the content stays free. Keeping in mind folks with data stream limits, I’ve used smaller images, but you can click through them to larger versions if you wish, or you may see the entire project folder here for super large images.
How to make bath bombs:
Everybody loves bath bombs. It is like taking a bath in champagne, only without the show tunes and chorus boys. They are fairly simple to make, keeping in mind that the strangest things can make a batch go weird; humidity, room temperature, oil viscosity, the moon rising in the seventh house of Aquarius . . . they are a mysterious wonder.
For this recipe, I am using ingredients that are pretty common, or easy to find in most areas. Essential oils can be found in small amounts at places like health food stores and craft stores often carry essentials and fragrances. Just make sure, if you buy fragrance oil, that you are buying “body safe” oils and not stuff for candles or oil warmers. Citric Acid can be found at health food stores, brewer’s stores, and online at various retailers.
So, let’s start with a basic recipe in two parts.
Dry ingredients: (By Weight, as measured on a scale.)
- Baking Soda – 8 ounces
- Citric Acid – 4 ounces
- Corn Starch – 4 ounces
- Salts – 4 ounces ( in these pictures, I used Dead Sea Salts, but mineral salts work too, and are easier to find and significantly less expensive.)
Wet Ingredients:
- Water – .75 tbsp
- Essential or Fragrance Oil – 2 tsp (for these I used a Ginger Peach.)
- Oil – 2.5 tbsp (I used cherry kernel, but any light vegetable oil will work.)
- Food coloring – 1 or 2 drops. (Your color will look very dark in the emulsion, but will be light in the fizzies, so as to not leave rings around the tub. For this batch I used one drop red and two drops yellow. The final result will be very light peach.)
step 1 – Blend the Dry Ingredients
Begin by putting all of your dry ingredients into a big bowl. Glass is best because it is non-reactive. Whisk or pestle those pesky clumps out. You want a fairly smooth consistency throughout the entire mix.
step 2 – Mix liquid and blend dry and liquids together
Blend your wet ingredients together. I usually use a small jar and shake it up. Don’t worry about separation too much, you are not going to get a full emulsion. Then, while whisking, slowly add small amounts of the liquid to your dry ingredients. Here we see my faithful Igor prepare to pour.
step 3 – Try to avoid creating volcanoes
If the mixture starts to foam, you are adding the liquid too fast. Quickly whisk the reacting ingredients into the nonreactive part and you should be able to stop the reaction. I add about a teaspoon at a time. When all of the wet ingredients have been added, you should have a mixture with the consistency of slightly damp sand. It should clump together when you squish it.
step 4 – Mold quickly
Once your mixture is together, you have a pretty limited amount of time in which to get it into molds. To create the giant Soapy Hollow ball of bath doom, I use round christmas tree ornaments that were designed to be filled with goodies. To do a three-dimensional bomb like these, you pack each side, then overfill a tad at the center and press the two sides together.
It takes a little practice to get a feel for how much filling you need, so don’t get discouraged if your first couple fall apart. Here we see Igor holding a filled ball and wondering about child labor laws.
step 5 – Unmold and let dry
You don’t need to leave them in the mold for very long, and in fact can tap them out as soon as you fill them. These are four bombs we made with this batch.
You can use all sorts of things to make your bombs; muffin tins, ice cube trays, candy molds, Aunt Magnolia’s denture case . . . whatever makes you happy.
This batch didn’t make quite enough for five bombs, and the humidity levels made the batch start to puff up, so I quickly stuffed what was left of the batch into my “bath cookies” mold. Note: When using things like silicon trays that surround the seltzer mix, or any mold with a lot of details, the mix must stay in the mold until dry, or it will crumble when you try to take it out.
Once they are completely dry, store bath bombs in an airtight container or bag. High humidity will make them activate. Because we used oil and water and no preservatives, you want to use them within about 6 months. Assuming you can keep them for that long. Igor demands payment in immediate fizzy baths, but you may have better luck actually getting to *use* yours.
When you’re ready to use one, just drop it into a warm bath, and relax.
Feel free to ping me if you run into any trouble, and I’ll be happy to help you troubleshoot!
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I have made 4 different batches of these and I cannot get them to dry hard.. Every batch has been firm but will crumble if touched too hard even after 2 days of drying.. I have sifted my ingredients, not sifted my ingredients, added a spritz of witch hazel.. any ideas??
Bath bombs are so finicky. When I’ve reviewed my batch logs; I’ve discovered that if my humidity levels are really high, they tend to pre-activate, or get really crumbly. Also, you have to pack them super hard. Some of the best bombs I’ve made are when I’ve used ice cube type trays, and just smooshed the mix in with a pestle.
Here’s what I would try: 1st, try adding a little more corn starch to your mix…that will help if it’s a humidity issue. 2nd; If that doesn’t work, try using a spray bottle to dampen the mixture instead of pouring it in. If you’re still having trouble, as strange as this sounds, try using a different essential oil or fragrance oil. Some fragrances are really problematic, and if you’re using something that has an alcohol base, that may be throwing off your recipe.
If none of those work, let me know, and we’ll try troubleshooting step by step and see if we can get it where you want it! Good luck! Just keep in mind that bath bombs are the souffle of the soap universe; they are finicky, and even when you do everything right, sometimes they just misbehave. It’s not you, I promise…it’s just sort of a tricky craft because the environment plays such a huge role in success.
Oh…also, don’t throw away the ones that crumble; if you mix the crumbles with some bath salts; you have fizzy bath salts. Add some mineral salts / sea salts to a glass jar. Add just a drop or two of color and shake it up, then add your crumbles and shake it up. Pour that mix into pretty jars…and poof! Instant gifts.
Hey, i just made an attempt at making a bath bomb but when i used it, it didnt seem very soappy. can you suggest somethong i can put in them to make them soappy?
Thanks
How long do you need to leave them to dry in a silicone mold?
Hiya Kayleigh, These bath bombs don’t have any soap in them, so they won’t be bubbly or soapy. You can try adding a detergent powder to make them soapy, but I’ve never had much luck trying it. I’ve a friend who makes something similar though, I’ll see if she’ll share the recipe.
I usually leave them in the silicone mold until they are completely dry…about 24 hours should do it, unless they’re really big. For hard molds, like the ball shaped ones, I pop them out almost instantly and let them dry outside of the mold.
Hi,
I tried these yesterday and today they are splitting. any ideas as to why? We are humid here in AZ. but not as bad as other parts of the country. I had a little trouble getting them out of the mold. Finally did and let them sit overnight. Today they are all getting a crack from the bottom up. When I squeeze them they seem hard and dry, but maybe a little moist in the center and they crumble apart.
Thanks in advance for any suggestions you may have. I hope to figure them out for a gift for my niece who just turned 13.
Hiya Jodi,
Good luck!
Bathbombs can be so tricky, that it’s often difficult to diagnose problems long distance. A lot can depend on the types of salt you use, the age of the starch, etc. Even though I’ve made thousands of these things, I still have batches that just don’t come together the way they should. Consider getting a little mister bottle, and putting some witchhazel in it. Spritz your mix just before you fill your mold, then before you seal your mold, spray both sides of the ball, then press the mold together. See if maybe that helps.
Hi,
What is the perfect humidity level for drying bath bombs and how long? I have a dehumidifier, so one day the bath bombs look great, the next day they are cracked. So, if you know the best humidity level, I would appreciate it.
Best regards,
Geri
Hiya Geri, I’ve had them work when the humidity was as high as 80% and had them fail at the same level.
They really are finicky beasts, and each batch can vary so much just because of ingredient vagaries. I treat bath bombs a lot like I treat making French almond pastry, I try to avoid starting a batch if the humidity is over 70% or below 40%, but sometimes we just gotta do what we gotta do, ya know? 
I’ve not tried a dehumidifier, but I suspect that using one would dry the outside too fast, leaving the inside damp, and therefore the entire ball becomes more likely to crumble. If the weather is really humid, I leave them in the mold to dry completely (48hours or so). I hope that helps!
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I tried making these bath bombs from this recipe but they turned out way to sticky and wouldn’t come out of the moulds and they kept expanding and reacting when I added the water. This resulted in them not reacting when I put them in the water, please can you tell me what I might have done wrong?
Hi OrangePanda, Bath bombs can react to all sorts of things. They really are the french macarons of bath products.
It sounds like you had too much water/liquid in your batch. It should feel like barely damp sand right before you pack it. If it feels wetter than that, try adding a tsp of cornstarch to your blend. Also, never try to do this project if your environmental humidity is above about 60-70%. The ingredients will pull moisture from the air.
If you live in a high humidity area, for example, by the ocean, the try adding your wet ingredients to your dry ingredients using a mister/spray bottle, instead of just adding it in. That should help you get to the right consistency. Good luck, let me know if I can be of any other help!
Hi, I successfully used this recipe a few years ago yo make bath bombs as presents. They turned out brilliantly and I used silicon molds for them. I’ve recently tried making a few batches of them , again in silicone molds. However they crumble when coming out of the molds. I’m baffled with what I’m doing wrong. I’ve left them to dry over night and they still crumble…any advice welcome, are they likely to be too wet/too dry? I’ve made balls by hand out if the same mixture and that has stayed together fine! Thanks in advance
Hiya Mary-Kate,
Try reducing your cornstarch by a tablespoon or so, and see if that helps. Alternately, try upping your liquids ratio by 1/2 tsp to 1 tsp. It sounds to me like the mix is just a tiny bit too dry, and while a dry mix will hold together when packed well/hard, it can be difficult to get a firm pack in silicon molds, especially if the local climate is dry.
I hope that helps. If not, let me know, and we’ll try some other things.
Cheers, DeAnne
Hi, I made bath bombs that way few times already. they came out good, but after few weeks i notice that i can not smell the fragrance anymore. instead they smell like baking soda or citric acid. why is that?
Hiya Diana,
That’s going to be a result of the fragrance you used. If you used a perfume, or anything that had a perfumer’s alcohol base, then the scent will evaporate really quickly. If you used an oil, and your scent is fading that quickly, you should contact the oil seller and report it. I have bath bombs that are 10 years old on the lab shelf (just because I want to see how long they’ll last), and they still have a scent. Let me know if you have trouble finding a good essential or fragrance oil vendor, and I can recommend a few for you.
Cheers,
De.
Hi DeAnne,
I tried making bath bombs with Dead Sea salt and they didn’t turn out too well. They became soft and damp where the salts were. I’ve heard theories that this is from the mineral content in the salt. How do yours turn out when using Dead Sea salt?
Hiya Hunter,
The trick with dead sea salt is to make sure that you run it through a grinder first. The structure of the crystal in dead sea salts will trap water, but, if you break the crystalline shape with a quick grind in either a coffee grinder or food processor or even mortar and pestle, you shouldn’t get damp pockets.
Hope that helps!
De.
Hi DeAnne, I don’t have any money so I am trying homemade Christmas gifts. Thanks for the Bath Bomb idea
I bet my siblings will love them!
Merry Christmas and happy New Years!!! Oh, and good luck to everyone trying to make a bath bomb.
Good luck! Let me know if you run into trouble.