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.
no matter what I do my halves will not stick together.
Hi Gigi,
Have you tried overfilling both sides, and then mashing them together? You’ll get some that will fall off as the mold sides come together.
Make sure you don’t twist the molds when you’re putting them together, or pulling them apart.
If neither of those works, then use a little less stuff inside the mold, close the molds completely, and let the mix dry in the molds. That’s sort of a last-ditch solution though, cause you need a 5 molds for this batch.
Also remember that the recipe can be impacted by your climate…so if you’re somewhere really dry, you might want to use a spritzer bottle with a little witchhazel, spritz the middle part right before you put em together and see if that helps.
If none of that works, lemme know and we’ll try to troubleshoot it.
Its still on instructables though?
Graham…so it would appear. Hmm.
Hi, your site is great; I really want to try the bath bomb recipe (they are expensive to buy, so making my own sounds like a fun, cost saving approach
). I was wondering if there is a recommendation for finding the molds inexpensively ~ it seems as though the places I’ve checked so far (online) seem to have steeply priced molds. Also, I was wondering if there is a difference in the essential oils at different stores ~ I saw some at the drug store, others at craft stores, and I believe even Bath and Body Works. I am a complete newbie at all of this, so I wasn’t sure if there was a marked difference in them or if the brands are just higher quality than others (my concern is that I’d end up getting something intended for non-skin contact and end up with some funky rash or something).
Hiya Nancy!
I would go with essential oils from a company that caters to the bath&body manufacturing community. For small purchases, I would probably recommend Camden Grey for the best pricing. I’ve also really liked products from Majestic Mountain Sage for high quality, but they are pricey, and I’ve had them flake on a order or two. Also Brambleberry has a good selection and you can buy in small amounts. I love their fragrance oils and highly recommend those, but generally buy EO from Camden if I’m buying in small amounts.
If you start buying in large amounts (more than a pound at a time), I can hook you up with some other really amazing suppliers, but they have large minimum purchases.
For the molds, these guys have the best price I’ve found for the 80mm size.
Hope that helps! Please feel free to ping me with questions! Cheers and happy soaking!
I left my bath boms in the plastic moulds overnight and now can’t get them out!!!!!
Some of them I’ve been able to get 1 half of the mould off but i can’t get the other half off!!!!
Any suggestions or tips on how not to do this again??????
Hiya Kelly,
Yep, I’ve had that happen in a mold before. Grrr, no? I try not to leave bombs in fully enclosed molds, because this can happen, but if you do leave them in a fully enclosed mold, like the christmas balls, before you try to get them out of the mold, tap the mold gently on the counter…about half the force you would use if you were cracking an egg.
You don’t want to whack it, cause you could crack your mold, or break the bomb. Just a gentle sort of tapping all the way around the perimeter opposite of the dividing line. (The two halves meet in the middle, tap in a vertical perimeter.)
That should break any vacuum that has been created inside the mold, and they should release a little easier.
Also, if you think you’ll be leaving them in the mold, it doesn’t hurt to brush a very fine coating of oil on the mold, which makes it easier for them to slide out when you’re ready for them.
Hope that helps! Feel free to ping me if you need any more help!
Thanks a lot for that – will try tonight!!!!!
Hi, could you please tell me if it would be all right to use vanilla extract or rose water instead of the essential oils? I really do not like the smell of the essential oils that they sell at my local health-store and I prefer the smell of vanilla or rose (the rose essential oil they sold smelled horrible in my opinion. Are essential oilds necessary? And do you think the alcohol in the vanilla extract will react with the ingredients?
Yeah, Rose Attar is super rare and unbelievably expensive…(around $3,000 a pound). Most places that sell “rose oil” are selling a synthetic oil. I agree that most of them smell icky.
There are a couple of companies that manufacture an amazing synthetic rose, but they can be really hard to find. IFF makes the best ones on the market, but they only sell in 50 gallon barrels, which…I mean…that’s a lot of fragrance. 
Majestic Mountain Sage and Brambleberry, I believe, sells IFF oils, if you ever decide to try a synthetic.
That said; the vanilla extract may or may not work…I’ve had batches that worked, and batches that just smelled awful after a few weeks. If you want to do a vanilla, the best way I’ve found to do it is to either use a good madagascar vanilla bourbon, or to take some 1/2 cup vodka and scrape the interior of a vanilla bean into it, then soak the interior and the exterior in the vanilla for a few days/weeks. Strain and use.
Assuming the rose water is just rose water without additives like sugars and whatnot, it should work.
Using either of those, note that you may need to add a little bit more of your carrier oil…like any recipe, when you make changes, you may have to tweak it a bit to get it to do exactly what you want.
Have fun, and come back and tell me (show pics!) of how it worked! Feel free to ping me with questions or problems!
receipe worked great:
(sodium bicarbonate) + (citric acid) –> (sodium citrate) + (carbon dioxide) + (water)
does sniffing the exploding fizz cause any inhalation of the produced sodium citrate? i read it is toxic to lungs and mucous membranes.
thanks!
No. Sodium Citrate and Citric Acid are the same thing…and it’s not toxic. According to the FDA, it can be “mildly irritating if the powder is inhaled directly”. The Safety Data Sheet says: Breathing in dust may result in respiratory irritation. May be irritant to mucous membranes of the respiratory tract. It goes on to say:
Acute Oral LD50 (ingestion)
Eye Irritation: Slightly irritating
Skin Irritation: Non-irritant
Mutagenicity: Not mutagenic
Carcinogenicity: Not carcinogenic
Reproduction: Not teratogenic
NOTE: GRAS – (generally recognized as safe for human consumption)
Thus, unless you were pretending to be Keith Richards on a bender in the 70′s, and sniffing lines of it…you’re in no danger.
The equation is: 3NaHCO3 + C6H8O7 –> C6H5Na3O7 + 3CO2 + 3H2O
Citric acid (C6H8O7) and sodium citrate (C6H5Na3O7) are different compounds.
Wikipedia says, “Contact with dry citric acid or with concentrated solutions can result in skin and eye irritation, so protective clothing should be worn when handling these materials.[citation needed]”
~ http://en.wikipedia.org/wiki/Citric_acid
I found my citric acid to have clumps in which I had to pestle out. Didn’t think I needed to be careful with touching it with my bare hands.
?
Well..no. That chemical formula is for Trisodium Citrate. It is sometimes referred to simply as sodium citrate, though sodium citrate can refer to any of the three sodium salts of citric acid.
Citric acid or any of the sodium salts of citric acid can be irritating to the skin in the same way that lemon juice or lime juice can be irritating. I’ve never had any issues, and I’ve done thousands of bath bombs. However, if it concerns you, or if you have any irritation, you can always wear food safe gloves.
Deanne,
thanks for the recipe… it is so nice we people share
and I just have to say you CRACK ME UP!!!!
I really LOVE your snarky random comments that really make one read your whole post… ie, a reader may be confused even alarmed if while skimming your post they catch notes about 1970 Keith Richards and child labor
hee hee
Hee! Thanks!
I love when people *get* my voice. 
Thanks for the kind words, and please, feel free to link photos of your finished bombs here so you can show em off!
i love your website!!!
if i ust wanted to make one or two fizz balls what should i do???
i love your website!!!
if i ust wanted to make one or two fizz balls what should i do???
You could try cutting the recipe in half, but this is the smallest batch I’ve been able to get to work successfully. If working smaller, I wouldn’t add liquid to the dry, I would use a spritzer bottle and spray to get the dry to stick together.
Good luck, lemme know how it works!
THANKS FOR THE FANTASTIC TUTORIAL – MY DAUGHTER & I ARE ON OUR 3RD BATCH.
CHANEL NO.5 FRAGRANCE THIS TIME – ABSOLUTE FAVOURITE IS SALTY SAILOR (think Calvin Klein One) available from BigTreeSupplies.com.au for all the Aussies – cheap moulds too !
Yay! Glad you’re having fun with them!
Hi,
Where can I find 80 mm bath bomb molds in the USA?
Thanks
Iris, Sunshine Craft, at this link: http://www.sunshinecrafts.com/dept_view.php?DPath=HOLIDAY~CHRISTMAS~ACRYLICORN&Page=1, seems to have the best price and most availability.
Thanks so much!!!!
Hi, I think I emailed you and mentioned that my bombs finally work, I was letting them dry in the enclosure and for sure they would fall in half. I just LOVE, LOVE LOVE, bathbombs. check them out and leave me a comment.
The url you left was to log in to your site, which is probably not what you wanted. For your data security, I deleted that url so it wasn’t grabbed by bots. I’d love to see your bathbombs though, if you want to try again.
As a rule, no site link should include username @ sitename.
Hi
or could you tell me where to get some? I have corn flour and tapioca starch. Do you think these will work?
I also love your site (and your sense of humour!) I am about to start making my first batch of bath bombs (wish me luck)
I was wondering if you can substitute corn starch? I cant find it ANYWHERE!
Your advice is appreciated
thanks
AAAHHHHH…… HELP!!! my bath bombs are expanding…. very quickly!!! what have i done wrong?
Corn starch should be in any baking section of the grocery store. It’s a super common ingredient (and really inexpensive). It the UK, cornflour *is* corn starch, but in the US, corn flour is corn meal…and I’m not sure which you’ve got. Flour doesn’t work, it gets gummy…and tapioca gets kinda slimy. Best bet, look on the top shelf of the store above the flour, and there should be a small container of corn starch. Lemme know if you can’t find any, and I’ll see if we can’t find you a local vendor.
Oh man, I hate when that happens! It’s cause the mixture got too wet, or the humidity was too high, or the chaos gods were laughing at you…there’s no telling what will set off the chemical reaction, but 9 times out of 10 it’s because the mix is too wet for some reason. However, don’t get discouraged, these are tricky beasts, and even after making thousands of them, sometimes my batches will just go off, puff up and refuse to cooperate.
Ah science, she’s a tricky mistress. 
I cant find it anywhere! (corn starch) I have tried a couple of local supermarkets (im in australia) and even tried health food stores but people keep telling me to get corn flour!
Ah, Oz is gonna be like the UK as far as naming protocol goes. Corn flour should work in your local. Try it, and then ping me back, so I can add that bit of knowledge to the database about world ingredients.
This looks like a great recipe and I can’t wait to try it! Question though – should the salts be fine or coarse? Or doesn’t it matter? This is a great project for my daughter and I to make for Christmas gifts. Thanks for sharing!!
Susan, I find that, within reason, crystal size of the salts doesn’t matter too much. I like to use dead sea salts, and I run them through a grinder until they’re about the same size/consistency as kosher salt. I’ve not had great luck with grains as small as table salt, but bath fizzies are so temperamental that they react differently for everyone, depending on humidity and all sorts of variables.
Just have fun! And share pics!
I’m definitely making these for Christmas! And quite a few for myself.
One question though:
Are “Bath Mineral Salts” the right kind of salt? Bath salts I can find everywhere!
Thanks so much!
Lauren, if you mean epsom salts, then yes, that works well. If you mean stuff that has already been colored and perfumed, then you might not have great luck. Bath bombs are so finicky.
Just made these! I thought you were using the biggest fill-able plastic ornament at Hobby Lobby though, so mine have turned out with a diameter of about six inches… This could be scary. I already got a really good Christmas present for the friend I’m giving these to though, so if they end up exploding her tub, she’ll think it was a prank!
I ended up using scented epsom salts (that’s all I could find), and I ground up some Crayola tub tints in the mix so they’ll turn the bath water bright colors.
I’ll let you know how they turn out!
Fantastic, can’t wait to hear! I’ve made really monster size one’s before…like the size of a softball. No worries on blowing up the tub.
Nobody ever lets me near anything that could actually explode. That’s like giving the Mythbusters a cannonball. Chaos will ensue. Hee! Happy Holidays, I’m so glad you were able to make something groovy! Yay!
Thanks for this recipe! My hubby LOVES bath bombs, but it’s rare to find them with “manly” scents. Although he’s reasonably partial to lavender and jasmine he worries it might make him smell too “girly” (boys can be so silly sometimes). He’d love something like tea tree or sandalwood. Going to give this recipe a go and see If he likes that
I’ve found in bath bombs that tea tree can smell kinda “medicine-y”. But a sandalwood-vanilla bomb not only smells amazing wafting out of the bathroom, but it leaves an amazingly warm scent on men. Yum.
Good luck, feel free to ping me with any questions!
Great tutorial! I shared your link at http://creativityunmasked.blogspot.com/2012/01/six-for-saturday-or-sunday_28.html
Hey Laura, thanks! Feel free to ping me with any questions you run across while making them, and I’d love to see pics of your finished ones!
I actualyl came tyhrough this from (de)Instructables, and I was wondering, being a man and all, the more fizz the better, is it the ratio of cornflour (I’m in the UK so cornstarch IS cornflour here just to confirm) to citric acid or just adding more citric acid to the mix?
Also what colourings do you recommend to get really vibrantly coloured baths?
Hiya WhiteHawksan,
Basically what you’re doing when making a bath bomb is combining a weak acid with a bicarb base…which creates carbon dioxide in the water…making the bubbles. Adding more of the acid won’t change the amount of carbon dioxide that’s created from the molecular combination of the acid and the base in the water. Best bet for *more* fizz in your tub is to add another bath bomb.
(The cornstarch is basically just a binder that allows you to add liquid to the other two items without having them instantly react.)
As to color; there are a few different options, but I have to tell you that vibrant colors tend to stain grout, and can even stain porcelain tubs. Do NOT use pigments. There are some dyes available from vendors like Brambleberry that may work, but be sure to read the descriptions carefully. Some FD&C powdered colors will work, but I think they might be tricky to find in the UK because I’m not sure they’ve been approved there. EU regulations on products are considerably more strict…an example I wish we followed.
Remember that the darker you go with color, the bigger the chance that you will permanently stain something in your bathroom, and may even tint your skin briefly. Did you ever dye Easter Eggs? And your finger tips would end up all blue and green and yellow and purple? Yeah. A vibrant color bath involving citric acid may very well leave you…erm, blue. (I’m so sorry, but I had to do it. I’ll get my coat…)
here in the UK we get ‘Lush’ bath bombs that will turn the water a very definite shade, I wondered what sort of colouring they were.
I think a faster reaction can be obtained by using a different base/acid reaction, perhaps bi-carbonate of soda might yield a more vigorous bubbles or a lower yield of cornflour to reaction mass.
I will experiment!
Oh you can get the water to color level X, by using soap safe dyes; but how rich you can get that color before it becomes a staining issue, I cannot say, as I’ve always been afraid to turn my bathroom purple.
As to fizzy experiments, please keep me posted, I’d love to know what you discover!
Well the bicarbonate of soda provided much more bubbles, although this batch I couldn’t get the mould to stick together. I also hardly used any cornflour (perhaps why it wasn’t sticking together?) I simpyl made a small ‘base’ of cornflour to pour the liquid on 1 tsp at a time, stopping it from reacting with the reaction mass and then quickly mixing it all together and repeating.
Yeah, the cornstarch is the binder in that recipe, bicarbonate doesn’t “stick” well. On the upside though, fizzy bath salts are just as fun as bombs.
can not wait to do this. xms on the way