How to Make Your Bath Bombs Harder?

Have you ever felt that your bath bombs don’t last long before they fizzle out in the tub? This might indicate that your bath bomb is too soft, so how would you make your bath bombs harder? 

Bath bombs can be made harder by reducing the water or replacing it with witch hazel. Other ingredients that help with hardening are cornstarch, kaolin clay, tapioca starch, or cream of tartar. Mixing and combining the wet and dry ingredients the right way can also contribute to a harder bath bomb.

Discover the ‘secrets’ Professional Bath Bomb Makers use to create luscious bath bombs with this step-by-step guide. You’ll have a priceless reference collection of product recipes with natural ingredients designed to create a relaxing spa atmosphere in your own home.

For a lot of people, bath bombs have become an essential part of taking a relaxed and healing bath after a long and tiresome day. So it’s essential that this experience lasts for as long as possible. So the next time your bath bomb is too soft, this is how you can harden them. 

Why won’t my bath bombs harden?

First, we must tackle why your bath bobs are not hard enough before we try to fix them. There may be several reasons why this happens. For example, it can be a direct result of adding too many or too few ingredients to the mix, which in turn can make the end result either soft or lumpy to handle. 

When this happens, you’ll usually end up with a bath bomb that is not only aesthetically pleasing but also not functional. 

Another reason might be that your bath bombs are stored in a humid environment or carry too much humidity, then the consistency of the bath bomb may stay too soft for usage and may even break or crumble when you try to take them out of the container.

Making sure that your bath bombs are nice and hard is a process that requires a mixture of wet and dry ingredients that need to come together in perfect harmony to make them harder and more durable. In the following sections, we will mention a few ways you can use to make them harder.

What ingredient makes bath bombs hard?

If you want to make your bath bombs harder, then there are some ingredients that might help you achieve that. For example, you can reduce the amount of water in it by replacing it with witch hazel, an ingredient that adds moisture to your bath bomb.

You can also include kaolin clay, tapioca starch, or cream of tartar, as this last one can also bring more fizz to your recipe. Other ingredients include cocoa butter and coconut oil, both of which can also add moisture to the bath bomb and help it dry harder. Other recipes mention the addition of more baking soda or citric acid to balance it all out. 

The key is not to overdo it with the wet ingredients so that the bath bomb doesn’t end up being so moist and soft that you’d have a hard time taking it out of the mold.

How to Make Bath Bombs Harder?

There are a number of things you can do to make bath bombs harder, which involve either adding or replacing ingredients, managing their place of storage, as well as the way in which all the ingredients are mixed together. 

One of the best ways to make bath bombs harder is to add cream of tartar or kaolin clay to the mix. Another important way to make bath bombs harder is to keep them from becoming too moist or too dry. To achieve this, you will have to be careful with the amount of water you put in the mix. 

Also, storing them in a dry environment (like an air-tight container) and avoiding humidity can help bath bombs to dry better and faster.

Sometimes, the order in which you prepare your ingredients can affect the final result. Make sure that both the wet and dry ingredients are well mixed together before combining both mixtures into the final mix. 

When you do so, always add wet ingredients a little at a time to make sure that the mixture is just right—this will help you create the perfect mix that is not too dry or too wet. 

Does cornstarch Harden bath bombs?

Yes, cornstarch is an ingredient that is recommended if you wish to harden your bath bomb. It should make up around 10% of the dry bath bomb mixture and can also be used as a thickening substance. 

Also, thanks to the presence of cornstarch (or cornflour) in its composition, the cornstarch binds itself to the baking soda and the citric acid, which in turn delays the bomb’s fizzing reaction by a few minutes and it does not explode as soon as it comes into contact with the tub water—so be careful not to overdo it, or the bombs will not fizzle at all.

If you don’t want to include this ingredient in your bath bomb, you can replace it with kaolin clay or tapioca starch.

How long do bath bombs take to harden?

Ideally, you should leave out your bath bombs for a minimum of 4 hours up to one night so that they can harden. Although, which is on the recipe you use, some make take between 24 to 48 hours, which is more than enough time to dry them out and be certain that they are as hard as possible. 

If you want to speed up the process, there are ways to do it fast and safely, you can find all the details in this article. You can also use the oven to dry your bath bombs which are known to be the most common way to dry bath bombs fast.

Another way to make the process go faster is using a hairdryer or a dehumidifier in case you live in a humid environment. The method you choose will depend on how fast you want your bath bombs to dry and harden.


In this article, we’ve given you some advice and tips that we hope will make the bath bomb making the process easier, and will lead to the results you wish. Getting your bath bombs to become harder is not an easy feat, but we are confident that with this information and with practice, you’ll get them just right.

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