Why Are My Bath Bombs Sinking?

Sinking bath bombs may be equally effective, but they sure are not pleasant to see. But why do your bath bombs sink? The answer to this is much more simple than you may think. 

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.

Bath bombs sink because the ingredients used may have greater bulk density than water, making your bath bombs sink quickly. Using ingredients with less bulk density, like corn starch, helps them float due to their lightweight. They may also sink if your bath bombs did not dry entirely. 

Making sure your bath bombs float might not be very important to you on a personal level, but if you are in the bath bomb-making business, this may negatively affect your sales. But luckily, the solution is not as difficult as most may think. At least if you are willing to change your recipes. 

Are bath bombs supposed to sink?

The general purpose of a bath bomb is to make it float. However, if sinking is not a concern, you can add any type of ingredient to your bath bomb as you wish. You’ll be able to make your bath bombs very sturdy, and you’ll get more benefit from them.

But when it comes to customers, things might be a little different. For most people, floating bath bombs can be entertaining and relaxing. So if your bath bombs sink right away, it is doubtful that your customers will order from you again. Therefore, controlling everything from the recipe mixing to drying is crucial.  

Why Are My Bath Bombs Sinking?

Bath bombs sink when they have a higher density than the density of water. This may be due to several factors:

The Ingredients Used In the Recipe:

Adding a greater quantity of liquid ingredients such as witch hazel or oil makes the bath bombs heavier. It is necessary to balance them by adding more amount of dry ingredients.

A higher amount of moisture in your bath bomb adds to its weight and causes the bath bombs to sink quickly.

The Packing of Bath Bombs in the Mold:

The technique used for molding the bath bombs might also determine the bath bombs’ floating or sinking ability. This means things like packing bath bombs too tightly in the mold may make it come out and dry as hard as a cannonball and causes them to sink.

The Time Given For Drying:

If your bath bombs do not dry fully, they will retain moisture, which makes them heavier. When moisture evaporates, they become much lighter in weight and are able to float on the water’s surface. 

It’s essential to maintain a humidity-free environment during the preparation, drying, packaging, and storing to prevent unnecessary moisture. If you have a humidity problem, investing in a dehumidifier is probably your best option. Or if you want to be sure your bath bombs are dried entirely try out new ways to get them dry.

In case you do not have the time to dry and want to get them out as soon as possible, there are ways to dry them quicker.

The Shape of the Bath Bombs

The shape of your bath bombs also determines the floating ability due to a principle called water displacement. There is no difference if your bath bomb itself has another shape like flat surfaces for example. The larger the bath bomb, the more water it will displace in the tub. Here the Archimedes’s principle comes into action, meaning that a lesser density of objects increases their floating ability. 

How Do You Keep Bath Bombs From Sinking?

Once you know the possible reason behind your sinking bath bombs, it becomes easier to solve your problem. Here are a few helpful tips and tricks that can make bath bombs float and fuzz.

Adjusting the Recipe:

Three types of salts can be used in the recipe: Kosher salt, Epsom salt, or common table salt. Kosher salt weighs less than table salt with the same quantity. As mentioned previously, the secret of making bath bombs that float is un using the ingredients with a lesser bulk density. 

This is why a bath bomb with corn starch will probably float, and a bath bomb made with cream of tartar will probably sink quickly. 

Packing the Molds:

Many bath bomb makers find it hard to believe that packaging and molding affect your bath bombs’ ability to float, but it’s actually much more important than you may think. Here are some tips on how to do it and what to avoid:

  1. Do not pack the mixture very tightly in the mold.
  2. If you have stainless steel molds, heap the mixture by stuffing the molds.
  3. If you use plastic clamshell molds, pack the mixture in the molds gently without packing it too tightly.

The denser you pack your bath bombs, the lesser the air pockets they form between their particles. Therefore, to incorporate a generous amount of air between your bath bombs dough, you should fill them gently in the molds.

To fill the bath bomb molds, lightly sprinkle your dough into each mold. By gently cupping the material by hand, create small mounds, and keep them aside. In the same way, prepare the next half of the mold and press them together gently.

Changing the Shape:

A round bath bomb has a compressed mass with greater density and lesser air pockets. Flat bath bombs have more space for air pockets and float for longer than round bath bombs.

A flat bath bomb has a greater surface mass to distribute the air pockets as a general rule. Therefore flat, boat-shaped bath bombs float better than round bath bombs. The easiest way to make floating, spinning bombs is to use stainless steel bath bombs molds. 

Drying the Bath Bombs:

Most people expect their bath bombs to become dry within 24 hours after they are made. If you want the bath bombs to float, it is better to let them sit for a few more days to dry entirely. If you don’t have the time to wait, you can use the oven to dry them quickly. 

The air pockets will not develop appropriately unless these liquids are dried thoroughly. Wet bath bombs are always more massive than dried ones.


You can prevent bath bombs from sinking if you adjust your recipe formulation. Ingredients with lighter density are a suitable choice for bath bombs that are intended to float and fizz. 

Pack and molding bath bombs loosely in the molds to have several air pockets is essential, so you’d have air pockets that help your bath bombs float effortlessly. 

Give your bath bombs a chance to dry until they lose all of the moisture. The humidity makes the bath bombs heavy and will make them sink immediately.

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