How To Make Bath Bombs Harder

Bath bombs fizzle and emit great fragrances when dropped in the water leading to an invigorating bath.

You don’t want that lush experience to last too short. So, what do you do? The solution is to make the bath bombs a little harder than normal.

But how do you do that?

The best way to make bath bombs harder is using ingredients such as kaolin clay and cream of tartar. Another way is to reduce the amount of liquid in your bath bomb recipe.

Also, keeping moisture out makes them last longer, and you can do this using silica gels and airtight storage containers.

The most desirable result is having a hard bath bomb that only loses the hardness once it stays long enough in water. The harder your bath bombs are, the longer they last, giving you much more luxury in the bath tub.

3 Ways To Make Your Bath Bombs Harder

To achieve this, you need to choose the right type of bath bomb (or make some correctly), then store it properly.

The following sections detail out how to make your bath bombs harder even when they’ve started crumbling.


For those of us who make our bath bombs at home, there are a few tidbits you need to put into consideration to have a good hard bath bomb that lasts long. The typical ingredients for a bath bomb include:

  • Baking soda
  • Citric acid
  • Water
  • Cornstarch or clay (such as kaolin clay)
  • Vegetable oil
  • Measuring spoons
  • Food coloring
  • Mixing spoons and forks
  • Medicine dropped
  • Bowls (about 4 are enough)
  • Muffin or ice cube tray
  • Optional ingredients to your liking such as fragrances and epsom salt
  • Warm water for testing the bath bombs.

We’re not discussing recipes here, but your focus when trying to harden bath bombs is to add the right amount of ingredients. Too much of one ingredient and you’ll not have the desired results.

The ingredients you need to keep an eye on are the wet ones especially oil and water. Too much of these ones and you will have a puffy or slimy bath bomb rather than a dry one.

If you are from a humid area, use as little of the wet ingredients as possible.

On the other hand, if you use too much of the dry ingredients such as cornstarch, the bath bombs will come out all dry and brittle. I found that adding cream of tartar in your ingredients makes the bath bombs harden better. Another option is to use kaolin clay as the basic ingredient of bulking them up.

Normally, the mixing is one and one third of a tablespoon of citric acid, two tablespoons of cornstarch, and two and two thirds of baking soda. If you choose to add Epsom salts, the mixture needs two teaspoons. These ingredients go into one bowl.

Keep in mind that Epsom salts, Dead Sea salts and other types of salts will absorb moisture from the air easily making your bath bomb crumble. It is advisable not to add them to the bath bomb for longevity.

The other bowl will have a teaspoon of vegetable oil, one teaspoon of water and 2 drops of food coloring. Fragrance should be added to this bowl at 15 drops.

Use wet ingredients that evaporate

For the wet ingredients, the general advice is to use the ones which evaporate fast to prevent the premature fizzing of your bath bomb.

Between water, oil, witch hazel, and alcohol, water is the hardest to use given that it quickly activates the ingredients leading to fizzing. You are thus better off using alcohol as it quickly evaporates leaving your bath bomb dry.

You then add the WET MIX TO THE DRY MIX and not the other way round. This way, you will know how hard the mixture has gotten. Ensure you dry the mixture well preferably overnight for the best results.

You can improve on the drying process by running a fan over it.


The storage conditions for your bath bombs play a major role in how hard and fizzy they will be when you take them out for use. Keep out moisture as much as possible.

Store in airtight containers

This means keeping the bath bombs in an airtight container or plastic bag as the first option.

Keep them in a cool and dry place at normal room temperatures (about 20°C/73.4°F). This can be in your cabinet, garage, or basement.

Other ideas include:

Use silica gel to store your bath bombs

Ever wondered why medicine, bags and other stuff come with little bags filled with small crystals? That’s silica gel. And its purpose is to absorb the moisture in the main product.

Chances are that you have one or two silica gel bags laying around. You can throw one bag into a container of bath bombs so that they suck up any little moisture in the air.

If your bath bombs seem to be crumbling, this will likely dry them up.

As a word of caution, do not drop the silica gel into your bath water when having a bath. It’s not good for your skin.

Blow-dry them

The other method for making bath bombs hard is using a blow dryer. The warm or hot hair from this little machine drys up any little moisture in the bath bomb to make it hard.

Make sure you don’t dry it too much since it could become brittle and likely crumble. A few minutes under the dryer will do the trick.

Use a dehumidifier

Dehumidifiers work by sucking the excessive moisture in the air in a given room. If you live in a humid area, these will be the best solution to keeping moisture off items such as bath bombs.

Make sure not to turn it all the way up as it can cause nasal irritation when the air becomes too dry.


If you store your bath bombs properly, they will serve you for quite a while. In the best storage conditions, you can use them up to six months after you bought or made them.

If you store for more than six months, the bath bombs will start losing their freshness and fizziness even with the proper storage conditions. This is because the ingredients in the bath bombs will begin deteriorating with some natural ones going bad.

Here, some think that adding a preservative to the mix when making the bath bomb or after buying it will extend its life. The truth is, citric acid is one of the best natural preservatives and it is already added to the mix.

Preservative such as Polysorbate 80 only add undesirable side effects to your bath bombs.

Ingredients Ratios Are Key

With these methods, you are assured of dry and safe bath bombs every time you need to use them.

The trick is in mixing the ingredients in the right amounts and storing them properly.