Bath Bomb Questions

I've been experimenting with bath bombs for a few weeks now, and I'm having such a hard time with making them fizz well. They also don't harden after a week of drying out; they are still soft enough I can dent them with my fingers. Here's the recipe I've been using (by weight):

4oz baking soda
2oz citric acid
2oz corn starch
2oz mix of epsom and dendritic salts
.5 oz avocado oil
.5 oz polysorbate 80
.2 oz fragrance oil

My questions are: how can I tweak the recipe to make the bath bombs more fizzy? Do I add a 1:1 ratio of poly 80 to avocado oil, or a 1:1 ratio of poly 80 to avocado oil and fragrance oil?

I don't make a ton of bath bombs, hopefully someone with more experience will be able to chime in as well.

The thing that jumps out to me is that you have a ton of salts and cornstarch. Everyone's "proper formula" is different but that's where I would start tweaking. PS80 is not going to add any fizzing, it's only purpose is to get your oils and colorants to mix with the bath water instead of floating on top.

Addressing the salts directly, Epsom salts need nearly 2c to be considered therapeutic. If you are adding Epsom salts for therapeutic use, it's not currently working. At most they're working as a filler (I don't use dendritic salts and haven't done the research to know what they might bring to the party). Cornstarch can add to hardness but I feel you probably have too much. I also don't use cornstarch and can't offer more advice about it.

My suggestion would be to decrease your cornstarch and salts to 1oz total or even less. You could also add SLS/A or cream of tarter to that 1oz of additives to boost some fizz. Again, I can't offer too much advice about it, my bath bombs are literally baking soda and citric acid. I am also refraining from commenting on your oil components since the weather plays a big role in how much to use (from your phrasing it doesn't seem like you have troubles with the bombs holding together, just the hardness).

I suggest leaving out the Epsom and dendritic salts. Instead of avocado oil, I use melted cocoa butter.

I read that cream of tartar can inhibit fizz, but I decided to try a bit of it anyway and did not notice a difference, myself. But then I only used about a quarter teaspoon because it was a small spice bottle and I didn't have much.

I also read that Corn Starch can contribute to yeast infections, so decided to leave it out of my last batch for my granddaughter. I don't know if that is true that it contributes, as I don't find a lot of corroborating evidence, however I do find some info suggesting that it can aggravate an already existing condition, so thought, leaving it out might be a good idea.

My most recent recipe I used was only Citric Acid and Baking Soda (plus oil, FO & Colorant), and I got a VERY fizzy Bath Bomb. But it didn't last long. I think other additives tend to make the fizzing last longer; slow them down some, so it lasts longer.

As for why your Bath Bombs aren't drying, perhaps your area is too humid? Or perhaps you need to use less liquid when making them? Or both?

salt in bb will attract the moisture

Thank you for the replies! I live in a very arid area (deserts of California) so humidity is not really an issue. I will try decreasing the amount of salts and cornstarch and see if that gets me a fizzier bomb.

Is fragrance oil considered an oil when used in the 1:1 ratio of polysorbate 80 to oils?

I have just started making them.. some success.. some failure.. ones i made first are realy hard.. just the way they should be.. the last ones i made.. just crumble. I dont know if im putting too much or too little oil in them .. im also adding some Kaolin clay powder as ive heard that help harden them.. but these last ones are really crumbly..??

Kaolin very often make them crumble, a lot of people do have problem while using Kaolin

I use a bit of kaolin in mine and fortunately have pretty good luck with it. It's taken me a long time to find the perfect recipe. If you post your recipe as well as any additives we can help you troubleshoot. If they are crumbling they probably don't have enough oil/butter in them. Now mind you, I don't make a lot of them anymore as they aren't good sellers here. Plus you can buy them really cheap at any store these days.

shunt2011 said:

I use a bit of kaolin in mine and fortunately have pretty good luck with it. It's taken me a long time to find the perfect recipe. If you post your recipe as well as any additives we can help you troubleshoot. If they are crumbling they probably don't have enough oil/butter in them. Now mind you, I don't make a lot of them anymore as they aren't good sellers here. Plus you can buy them really cheap at any store these days.

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I may try adding coconut butter as its more of a solid butter rather than an oil.. it may help stop them crumbling..

Another question too.. hope i'm not asking too much here.. I have seen here many bath bombs with insets in the top with either soap flowers or soap miniature items on the top, NOT inset into it as such, but sitting in a inset of the bath bomb, like a bit has been cut of, a round inset made in the bomb before the soap flower or little items have been put in. Just wondering if there's a mould with an indentation to make the top with that hole in, or if it has to be made as a sphere, left to dry and cut out manually.. like the one in the picture..

You would need to adhere with something. I've not seen one like that. I know that most just put like lavender buds into the bottom of the mold first then add their bath bomb mixture on top. I've not tried anything like that a I don't like floaties in my bathtub.

Maybe you could adhere a small top, like a water bottle cap to the inside of your mold to create the indentation?

SoapAddict415 said:

Maybe you could adhere a small top, like a water bottle cap to the inside of your mold to create the indentation?

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i may try that with one of the plastic moulds, i wouldnt want to ruin my metal ones.. Thankyou.. great idea.

Still having lots of problems making bath bombs.. i seem to wasting ingredients like they're going out of fashion.
I make 5 or 6 at a time.. Day after i only have to touch them.. and they crumble of are still so soft they fall apart.. Beginning to loose my patience with them.. I mixed 360gm of sodium Bicarb with 170gm of citric and 20gms of cornflour for hardening.. added 15ml of sweet almond oil with mint choc chip FO.. spritzed with iso while mixing all together.. and made into 5 bombs and 2 pyramids.. day after.. they still fell apart .. Can anyone see where im going wrong.. before i chuck away the whole stock..?

Paul Kimberlin said:

Still having lots of problems making bath bombs.. i seem to wasting ingredients like they're going out of fashion.
I make 5 or 6 at a time.. Day after i only have to touch them.. and they crumble of are still so soft they fall apart.. Beginning to loose my patience with them.. I mixed 360gm of sodium Bicarb with 170gm of citric and 20gms of cornflour for hardening.. added 15ml of sweet almond oil with mint choc chip FO.. spritzed with iso while mixing all together.. and made into 5 bombs and 2 pyramids.. day after.. they still fell apart .. Can anyone see where im going wrong.. before i chuck away the whole stock..?

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Im sure i will be corrected if im wrong and as i kinda lost interest fir the very reason your getting impatient they just went to dust. Most the recipes iv read use witch hazel this could be worth try. Given its winter here and it rains ALOT could it be where you are leaving them overnight? Maybe they are attracting moisture from the damp enviroment? These are just my guesses of possible causes and im hoping someone more experienced will chip in if im wrong

Paul Kimberlin said:

Still having lots of problems making bath bombs.. i seem to wasting ingredients like they're going out of fashion.
I make 5 or 6 at a time.. Day after i only have to touch them.. and they crumble of are still so soft they fall apart.. Beginning to loose my patience with them.. I mixed 360gm of sodium Bicarb with 170gm of citric and 20gms of cornflour for hardening.. added 15ml of sweet almond oil with mint choc chip FO.. spritzed with iso while mixing all together.. and made into 5 bombs and 2 pyramids.. day after.. they still fell apart .. Can anyone see where im going wrong.. before i chuck away the whole stock..?

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Paul, here is a recipe I got from the book, "Kitchen Chemistry." It seems to work for me every time.

No Fail Foaming Bath Bombs
1 cup Citric Acid (7.4 ounces)
2 cups Sodium Bicarbonate (17.3 ounces)
¼ cup of Sodium Lauryl Sulfoacetate (1.6 ounces)
¼ cup Cream of Tartar (1.4 ounces)
½ cup melted Deodorized Cocoa Butter (3.2 ounces)
1 tsp essential or fragrance oil

Note: Ounce measurements given in () are by weight.

Make sure to wear a mask or tie a handkerchief over your nose when working with sodium lauryl sulfoacetate as it is very powdery and can irritate bronchial passages. Mix all of the dry ingredients until there are no lumps and all is well blended. Mix in the melted cocoa butter and the EO or FO. Mix until all is well blended.

I use decorative individual silicone molds for my bath bombs and call them bath tabs. You can find them at a hobby store or at Amazon.com I let them set until they harden and then remove them from the molds. They stay together and are easier to remove from the mold. If you don't want to use sodium lauryl sulfoacetate, then just use 1/4 cup soda and a little citric acid to make up the difference.

There are molds for these.

I don’t know if there’s a difference between cornflour and cornstarch, but I always use cornstarch. It sounds like the bombs aren’t getting wet enough to hold together. Plus, (and this is big) I noticed you don’t have Polysorbate 80 listed in your recipe. If that was an oversight, just ignore the next paragraph.
Poly 80 is an emulsifier that helps the oils disperse in the water, and it prevents the mica coloring from clinging to skin or the tub. It also makes the bomb more foamy. It is a must have. I usually add it in at 1:1 ratio with the carrier oil, which for me is the almond oil.
If your powder isn’t holding together like damp sand, adding in a tablespoon of Poly 80 will help a lot. In my spray bottle, I have water & alcohol.
You just have to play with it, but the Poly 80 is a game changer. I put it in all my products, not just the bath bombs. Amazon has it for pretty cheap. Let me know if that helps!

Paul Kimberlin said:

Still having lots of problems making bath bombs.. i seem to wasting ingredients like they're going out of fashion.
I make 5 or 6 at a time.. Day after i only have to touch them.. and they crumble of are still so soft they fall apart.. Beginning to loose my patience with them.. I mixed 360gm of sodium Bicarb with 170gm of citric and 20gms of cornflour for hardening.. added 15ml of sweet almond oil with mint choc chip FO.. spritzed with iso while mixing all together.. and made into 5 bombs and 2 pyramids.. day after.. they still fell apart .. Can anyone see where im going wrong.. before i chuck away the whole stock..?

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Your recipe is good. A good tip is to add 2 teaspoons of water to your fragrance oil and stir. If you use a blender add it in slowly so it doesn’t activate. I know it goes against the rule of no water but it’s an excellent way to harden your bombs! They will crumble otherwise.

Livx said:

Your recipe is good. A good tip is to add 2 teaspoons of water to your fragrance oil and stir. If you use a blender add it in slowly so it doesn’t activate. I know it goes against the rule of no water but it’s an excellent way to harden your bombs! They will crumble otherwise.

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Sorry food mixer not blender.

Try 2 tablespoons oil, 2 teaspoons water and fragrance and mix them all together. Then add slowly to your recipe.

lsg said:

Paul, here is a recipe I got from the book, "Kitchen Chemistry." It seems to work for me every time.

No Fail Foaming Bath Bombs
1 cup Citric Acid (7.4 ounces)
2 cups Sodium Bicarbonate (17.3 ounces)
¼ cup of Sodium Lauryl Sulfoacetate (1.6 ounces)
¼ cup Cream of Tartar (1.4 ounces)
½ cup melted Deodorized Cocoa Butter (3.2 ounces)
1 tsp essential or fragrance oil

Note: Ounce measurements given in () are by weight.

Make sure to wear a mask or tie a handkerchief over your nose when working with sodium lauryl sulfoacetate as it is very powdery and can irritate bronchial passages. Mix all of the dry ingredients until there are no lumps and all is well blended. Mix in the melted cocoa butter and the EO or FO. Mix until all is well blended.

I use decorative individual silicone molds for my bath bombs and call them bath tabs. You can find them at a hobby store or at Amazon.com I let them set until they harden and then remove them from the molds. They stay together and are easier to remove from the mold. If you don't want to use sodium lauryl sulfoacetate, then just use 1/4 cup soda and a little citric acid to make up the difference.

Click to expand...

Thankyou ... i may just try this recipe..i havent added a butter as yet to any bath bomb..

KathrynS said:

I don’t know if there’s a difference between cornflour and cornstarch, but I always use cornstarch. It sounds like the bombs aren’t getting wet enough to hold together. Plus, (and this is big) I noticed you don’t have Polysorbate 80 listed in your recipe. If that was an oversight, just ignore the next paragraph.
Poly 80 is an emulsifier that helps the oils disperse in the water, and it prevents the mica coloring from clinging to skin or the tub. It also makes the bomb more foamy. It is a must have. I usually add it in at 1:1 ratio with the carrier oil, which for me is the almond oil.
If your powder isn’t holding together like damp sand, adding in a tablespoon of Poly 80 will help a lot. In my spray bottle, I have water & alcohol.
You just have to play with it, but the Poly 80 is a game changer. I put it in all my products, not just the bath bombs. Amazon has it for pretty cheap. Let me know if that helps!

Click to expand...

i have 3 ltrs of polysorbate 80.. i did actually put it in my first bath bombs.. they were okay.. its everything ive done since then, but as i didnt use mica, i didnt put any in.. i might just add it to every mix anyway.. Thankyou.
..
Determined to get there one day..lol..

Cornstarch is the same as Cornflour i'm led to believe, in the US its known as cornstarch, in the UK we call it cornflour.. a lot of ingredients go by different names so ive looked at loads of ingredients and made a list of what theyre called in the US against what we call them so as not to go wrong..