Bath Bomb Questions & Answers

bath bomb questions and answers

Bath bombs are great project for both beginner and advanced crafters. Making bath bombs is an easy process, but it takes practice. Bath bombs are sensitive to moisture and can be finicky. Without the right mixture of ingredients bath bombs can crumble, fall apart or fizz incorrectly. Below are some of the most common bath bomb questions we receive, along with links to other bath bomb posts!

Bath bombs consist of Baking Soda and Citric Acid. When these two ingredients are combined and introduced to water, they create a  fizzing reaction. The standard ratio is 2 parts baking soda to 1 part citric acid. Once the dry ingredients are combined, a small amount of liquid is introduced to create a moldable, wet sand texture. The liquid is usually Witch Hazel, but oils and butters can also be added for moisture and additional skin benefits. The bath bomb mixture can be further customized with fragrance, color and the shape of the mold. Now, let’s get to the questions!

Blue & White Bath Bombs

Bath bombs are created using baking soda and citric acid.

1. Why is my bath bomb crumbly or cracking?
If you find that your bath bomb is crumbly, the mixture may be too dry. Adding more witch hazel or oils will give the mixture a more moist texture, which will be less likely to crumble and crack once removed from the mold. If your fizzy is cracking after it’s been in the mold, it’s possible that it was too wet and the mixture is expanding as it sits in the mold.

Wet Bath Bomb Mixture Being Molded In Gloved Hand

The correct amount of moisture is crucial to a firm yet moldable bath fizzy.

2. Why is my bath bomb soft?
If your bath bomb is soft, the mixture may have too much moisture. If you add too much witch hazel or oil during the mixing process, add more dry ingredients to balance the texture. If you live in a humid, wet climate, the moisture in the air can prevent the bath bombs from becoming hard. Adding a small amount of clay (like Kaolin Clay) or cornstarch can help the bath bombs harden. They also make the bath bombs a bit more sturdy.

3. Why does my bath bomb have lumps, warts or bumps on the surface?
A bumpy texture on your bath bomb is usually a result of clumps in the dry ingredients or not fully mixing the fragrance oil. Baking soda in particular tends to clump together. Before adding oil, color, fragrance or other additives, break up large clumps with your hands. To remove and break up smaller clumps, pour the dry ingredients through a fine mesh sifter. This extra step gives a smooth texture. Bath bomb warts can also occur when the fizzy contains too much moisture. Usually the culprit is fragrance or essential oil so mix extra well to ensure the wet is fully incorporated into the dry.

4. Why is my bath bomb not fizzing very much?
If your bath bomb is not fizzing in the tub as much as you’d like, you may try increasing the amount of citric acid in your recipe. You can start with a mix of 2 parts baking soda to 1.5 parts citric acid. In addition, if you use cornstarch in your recipe, you may try decreasing the amount or eliminating it all together. Fizzing can also decrease if a large amount of oil is used. If your bath bomb comes in contact with moisture from the air or from a damp environment, the fizzing reaction can decrease. To protect it from moisture, wrap it tightly with plastic wrap.

5. Why is my bath bomb expanding out of the mold?
If your bath bombs are expanding in the mold, this means the mixture is too wet and the fizzing reaction is happening prematurely. If you use a colorant or fragrance that contains water, this can cause the bath bomb mixture to fizz. If this happens, the bath bombs may still may fizz in the tub, although the amount of fizz may be decreased. In addition, bath bomb mixtures can fizz prematurely due to moisture in the air. For example, if you make bath fizzies on a moist and rainy day, this can cause the bath fizzies to expand in the mold.

6. What colorants can I use?
La Bomb colorants are specifically formulated and designed for optimal bath bomb coloring. They’re made of the same highly concentrated FD&C and D&C dyes that LabColors are made of. Instead of being made with water the way the LabColors are, La Bomb colorants are made with Glycerin. That means when you add your La Bomb colorant to the bath bomb mix, it won’t start to fizz and make warts the way water-based colorants can. 

In addition to La Bomb colorants, you can also use MicasClays, or other natural colorants to color your bath bombs. Simply add the dry colorants to the bath bomb mixture and blend until completely combined. Keep in mind that powder colorants can leave color on your tub and on your skin. This is particularly true for larger particle colorants like Pigments. I prefer to work with micas or clays in bath bombs.

To help the color and oil mix into the bath water rather than pooling on top, we recommend the emulsifier Polysorbate 80. You can add it at 0.1 oz. per cup of fizzy mixture to start. 

Pink Colored Bath Bomb Mixture in Gloved Hand

La Bomb colorants are dispersed in glycerin, which does not cause the bath bomb to fizz prematurely. 

7. How much colorant can I add?
You can use as much colorant as you’d like. I like to start with a small amount and add more colorant until I achieve a color I’m happy with. Because baking soda and citric acid are white, it’s really difficult to achieve darker tones such as red or navy. To achieve a dark color, you’ll need to use a lot of colorant. That can lead to dark bath water, or leave a lot of color on your tub and skin.

8. What can I use in place of witch hazel?
If you prefer not to use witch hazel, oils are a great way to help give the bath bomb mixture a moldable texture. Some crafters use a mixture of 99% Isopropyl Alcohol and water to help give their bath bombs the correct texture. In particular, bath-bomb-maker-extraordinaire Holly Port is allergic to witch hazel, and uses a combination of alcohol and distilled water instead. 

Gloved Hand Spraying Liquid onto Green Bath Bomb Mixture

Some crafters use a combination of distilled water and alcohol in place of witch hazel to achieve the right bath bomb texture.

9. How much fragrance should I add?
To find out how much fragrance oil to use in your bath bomb recipe, you can use the Bramble Berry Calculators. Select the “Salts” option. Then, input how much bath bomb mixture you’re making (baking soda + citric acid + additional ingredients). Select the fragrance or essential oil you’re using and the calculator will tell you how much fragrance to use in your recipe. The Fragrance Calculator uses weight measurements, while some bath bomb recipes use a volume measurement, like cups. If your recipe is measured by volume, you can use your nose to determine how much fragrance to add! I like to add a couple drops, mix and then smell. If you want it a bit stronger, you can add more.

10. How much oil and butter can I add?
How much oil or butter you add to your bath bomb mixture is totally up to you. Adding oils and butters to your bath bombs adds skin-loving qualities to your recipe. Some people love the way oils feel in their bath water, while others may prefer no oil. If you like working with oils and butters in your bath bombs, they should be added after the dry ingredients (baking soda and citric acid) are thoroughly mixed and smooth. Make sure to melt down any solid butters before adding them to your mixture. Adding too much butter or oil can sometimes cause the bath bombs to stay soft. If you have never tried oil or butter in your mixture but want to, start with about .5 oz of oil per 1.5 cups of dry ingredients. Remember: oils in the tub can lead to a slippery tub when you get out so be careful when exiting the tub after an oil or butter-filled fizzy.

Gloved Hand Pouring Liquid Oil into Bath Bomb Mixture

Adding oils and butters is a great way to add skin-loving properties to your bath fizzies. 

11. Do bath bombs experience vanilla discoloration from fragrance oil?
Bath bombs can discolor due to fragrance oils with a high vanilla content, just like cold process and melt and pour soap. In my experience, vanilla discoloration in bath bombs is inconsistent and takes longer to appear. For example, in cold process soap, vanilla discoloration happens within days or even hours. While in bath bombs, the vanilla discoloration may not appear until weeks or months later. You can add Vanilla Color Stabilizer, but keep in mind it may not prevent the discoloration. To be on the safe side, you’ll want to use a fragrance that doesn’t discolor. 

12. What molds are best for bath bombs?
One of the most popular bath bomb mold options are two-part molds that create a spherical shape, such as the Stainless Steel Bath Bomb Mold or the Bath Bomb Mold & Package. If you’re looking to create bath fizzies with a unique shape, the best kind of molds to create bath bombs are sturdy, yet slightly flexible. Plastic molds with individual cavities are a great option. Silicone molds are an option as well. The Round Cupcake Silicone Mold can be used to make adorable bath bomb cupcakes.

13. How long should bath bombs stay in the mold?
I recommend leaving your bath bomb in the mold for at least several hours, up to overnight. If you try to remove the bath bomb while it’s still soft, it can crumble. Allowing the bath bomb to dry thoroughly in the mold will make it easier to remove and handle.

Gloved Hand Scooping Mixture into Mold

Molds with small individual cavities work great for creating petite bath fizzies.

14. Why are my bath bombs not sticking together in stainless steel bath bomb mold?
Sometimes it can be a little tricky to get the two halves of the bath bombs to stick together. Instead, the bath bomb mixture tends to stick to the mold. To help, add 5-10 drops of Cyclomethicone in both sides of the mold and swirl it around. Then, let the molds drain on a paper towel. It makes removing the mold extremely easy! The texture of your fizzies is also important. For the stainless steel molds, you want the bath bomb mixture to be a bit more wet so the mixture holds its shape. See the correct texture and how to unmold the mixture in the How to Make Bath Fizzies video.

15. How do I package bath bombs?
Bath bombs are delicate, so packaging them can be a little tricky. Popular options include using small boxesjars, and bags. The Bath Bomb Mold & Package is a great option as it acts as a mold and package all in one. Bath bombs store best in a cool, dry place at room temperature. Good options include a basement, garage, or cabinet. If you live in a humid climate, you may want to wrap the fizzies tightly in plastic wrap before putting them in a box or bag. The plastic wrap helps protect the fizzies from excess moisture. You can also pop a silica packet in the package with your fizzy. The silica packet will help absorb excess moisture. Just make sure whoever has the fizzy doesn’t throw the silica packet in the tub as well! Using a dehumidifier or running a fan over the fizzies as they dry helps too.

Pink and White Bath Bomb Inside Plastic Mold

The Bath Bomb Mold & Package, Plastic is a great option for packaging your bath fizzy, as it is both a mold and package!

16. How long do bath bombs last?
In general, try to use your bath fizzies in about 6 months. The longer you wait, the more likely it is the bath bomb will be exposed to moisture in the air and lose some of its fizzing power. Both citric acid and baking soda have very long shelf lives, but the citric acid can lose its potency. Citric acid will not lose its potency if it is not exposed to any air and is kept in an airtight container. This probably isn’t very feasible in most storage situations though, as humidity is fairly good at getting into the smallest and tightest spaces.  I would recommend using your citric acid within 6 months of receiving it to be on the safe side. There is nothing worse than making a batch of fizzies and finding them to be substandard in the fizzing department! In addition, keep in mind the shelf life of any oils and butters used within the bath bomb. 

Want to start creating your bath bombs? Bramble Berry has two Bath Bomb Kits that include everything you need to make about 15 bath bombs from scratch. Each kit includes essentials like Disk Mold & Package, PlasticSodium BicarbonateCitric Acid and Witch Hazel. Choose between the Natural Bath Bomb KitGlitter Bath Bomb Kit, Bath Bomb Cupcake Kit, or the Pearl Bath Bomb Kit.

Colorful Bright Glittery Bath Bombs next to Natural Light Pink Bath Bombs with Dried Rose Petals

Left to right: Glitter Bath Bomb Kit, Natural Bath Bomb Kit

But what really makes the bath bomb kits stand out is the extras – each kit comes with printed instructions, labels and a how-to video. As a bonus, they ship free to the lower 48 United States. They are perfect for beginners and more advanced crafters alike.