Bath Bomb Recipes

Bath Bomb Ingredients: Functions and Usage Rates

I often got asked “What makes a bath bomb fizz”?”Why do we need to add oil?”, “What is Cream of Tartar for?” etc, etc, etc. If you want to make bath bombs successfully you need to know what the function of your ingredient is. If you want to change your recipe and not end up with a big pile of mess you need to know what the function of your ingredient is. If you want to make your bath bombs foamier or more moisturizing or to slow down the fizz and make them last longer you need to know what the function of your ingredient is.

So in this post, we are going to talk about the most common bath bomb ingredients, their recommended usage rates, and their function. The usage rates that I mention in the table are approximate and are there just to give you my perspective. You’re going to see other bath bomb creators using these ingredients at different % and it’s totally fine. It doesn’t mean that they’re wrong. For example, if they decide to use only 4 ingredients in their bath bombs then naturally their baking soda and citric acid % are going to be higher than recommended by me. Just keep that in mind.

NameINCIUsage Rate (Approximately)β‰ˆFunctionNotes
Baking SodaSODIUM BICARBONATE56%creates fizzy reaction when used with citric acid
Citric AcidCitric Acid28%creates fizzy reaction when used with baking soda
CornstarchZea Mays (Corn) Starch4-15%slows down the fizzing reactionwhen used in large quantities might cause powdery bath bombs
Saltdepends on the type of salt you’re using2-10%slows down the fizzing reactionEpsom Salts and Ded Sea salts are humectants and they draw moisture into bath bombs. It’s not a bad thing if you live in a dry climate but it could be an issue if the humidity in your area is high.
Cream of TartarPotassium Bitartrate2-8%acts as a hardeneryou could substitute it for Kaolin Clay
Kaolin ClayKaolin2-5%acts as a hardenerwhen used in large quantities might cause bath bombs to crack
Milk Powderdepends on the type of milk you’re using2-8%creates foamyou can choose from a variety of milk powder: Coconut, Goat, Regular, Buttermilk etc)
SLSASodium Lauryl Sulfoacetate0.5-5%creates bubbles, slows down the fizz, makes your bath bombs last longerit’s a gentle surfactant.
SCISODIUM COCOYL ISETHIONATE 0.5-5%creates bubbles, slows down the fizz, makes your bath bombs last longerit’s a gentle, very mild surfactant aka Baby Foam. I also use it for making my Foaming Bath Whip from scratch.
NatrasorbTapioca Starch1-4%anchors your scent, helps to disperse your fragrance oils and essential oils, provides a soft feel to the waterIt’s not the same as Tapioca starch that you buy in a food store.
You typically need to mix Natrasorb Bath with your fragrance oils or essential oil in a 1:1 ratio
Colloidal OatmealAvena Sativa (Oat) Kernel Flour1-2%soothes the skinI like to add this powder to my Oatmeal and Honey Bath bombs
Oils and Butterdepends on the type of oil or butter you’re using1-3%moisturizes the skin, binds the mixtureit’s recommended to use a lightweight oil like sunflower, safflower, grapeseed, sweet almond, apricot kernel, etc for your bath bomb. But you could experiment and test different oils to see what is the best option for you.
Polysorbate 80Polysorbate 800.5-1.5%disperses oils and oil-soluble or insoluble colorants and glitteruse it in a 2:1 ratio with your oils (2 parts oil and 1 part Polysorbate 80)
Polysorbate 20Polysorbate 201-3%disperses oils and oil-soluble or insoluble colorants and glitterit’s weaker than Poly 80 so you should use it at a 1:1 ratio. More often than not it used for lightweight oils or fragrances.
Colorantsdepends on the type of colorant you’re using0.01-0.2%colors your bath bombs, foam, water depending on the type of colorant you’re usingthe most common colorants used in bath bombs are water-soluble dyes, lakes, and micas. Make sure your dyes and lakes are FDA certified for use in cosmetics if you are planning on selling your bath fizzies.
Fragrance oilsParfum1-2% (depends on the recommended usage rates provided by your supplier )makes your bath bombs smell nice
Essential oilsdepends on the type of essential oil you’re usingdepends on the type of essential oil you’re usingmakes your bath bombs smell nice and are known to have a therapeutic effect
Binderdepends on the type of binder you’re usingdepend on the humidity levelsbinds your mixture togetherYour choices are water, witch hazel, rubbing alcohol. When you use water then make sure to add it very slowly and mix fast to avoid activation of your bath bomb mixture. I need about 1-2ml of water per 500g batch.

Let’s take a look at one of my recipes. As you can see I included a surfactant (SCI) at a very low % so we are still going to get a pretty good fizzing reaction with nice, creamy foam. Do you want more bubbles? Add SLSA. Would you like your bath bombs to be very moisturizing? Include some kind of butter in your formulations. Your bath bombs are dry, they are cracking and you notice that the humidity inside your house is pretty low? You could solve this issue by adding more oil, using water as your binder, and reducing cornstarch.

I hope this information is going to help you formulate your own recipes, tweak mines, and understand why we add a certain ingredient to a concoction.

If you’re a beginner then here’s the list of suppliers and a basic bath bomb recipe with instructions.
If you’re interested in how to convert % into grams and why I use % for my recipes then this post is going to be extremely useful.
If you’re struggling with keeping track of your supplies, recipes, notes, etc then feel free to use my Inventory and Sales Tracking Base (it’s free of charge).

HOW TO MAKE EMULSIFIED SUGAR SCRUBS. THREE SCRUBS – THREE EMULSIFIERS

I often get asked about substituting emulsifying wax in certain products. While in many ways changing an emulsifying system can have a great impact on the final consistency of a lotion or cream, I found that in anhydrous formulations (body butter, body balm, emulsified sugar scrub) they mostly change the way the product slips on… Continue reading HOW TO MAKE EMULSIFIED SUGAR SCRUBS. THREE SCRUBS – THREE EMULSIFIERS

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