Why Are My DIY Bath Bombs Expanding?

  • Date: May 13, 2022
  • Time to read: 6 min.

Bath bombs are a great way to relax and pamper yourself. They’re also a fun, unique gift idea! While most people have had success with their bath bomb creations, others have breakage or expansion issues that can be frustrating. You’ve followed all of the directions given in tutorials online, from using distilled water over tap water, to adding the perfect amount of sodium bicarbonate. So why are your bath bombs still exploding?

One of the most common causes of bath bomb breakage is too much moisture. This could be too much witch hazel in the mixture, moisture in the mold or moisture from the air. Bath bombs need a dry, warm atmosphere to harden properly after they are molded. The humidity level in the air can cause bath bombs to expand or break apart.

Why do bath bombs expand?

Why do bath bombs expand?

If you find your bath bomb expanding or your asking why is my bath bomb soft, then you might have too much moisture when you make bath bombs either in the mixture or the air.

When I started making bath bombs I didn’t consider the day or the atmosphere at all, but actually its critical to make dry bath bombs on a dry day!

Too much water when making bath bombs

If, when making your bath bomb you’ve added too much water, the mixture will likely expand or break apart when it’s in water. While this is rare, it can be an issue if you accidentally add too much distilled water to your bath bomb mixture. If this happens to you, try adding more dry bath bomb ingredients to absorb excess moisture.

If you are struggling with expansion or breakage issues, try using a stainless steel molds. Molds help create a more uniform shape and size which can reduce expansion or breakage from changes in the air. They’re also great for making unique shapes which is perfect for gifting!

Moisture in the air

This is another common reason why bath bombs can expand. If you want perfect bath bombs you have to consider that they will absorb moisture in the air into the mixture. Some people choose to leave them next to a air conditioner or even dry them in the oven to make the bath bombs harden.

Water in the molding mixture

If too much water is added to the bath bomb mixture, it will begin to expand when in a mold. If you feel like your mixture is a little moist after all of the ingredients have been mixed together, add a small amount of baking soda and citric acid to soak up any excess moisture. There isn’t an exact ratio forthis mixture but generally, somewhere around 1 tablespoon of baking soda to every 1 tsp of citric acid is a good starting point.

Can bath bombs be saved?

Can bath bombs be saved?

It can sometimes be possible to save imperfect bath bombs if they expand in the mold. To do this, allow the bath bomb to fully dry and then pop it out of the mold.

Once out of the mold, gently squeeze and smash it back together with your hands. If the bath bomb still feels moist or there’s a small crack in it, you can also add a bit more citric acid and baking soda mixture to help dry up any excess moisture.

Alternatively keep these failed bath bombs for yourself, I often have a jar full of bits that I make lovely baths with.

How do you keep bath bombs from expanding?

  • keep your bath bombs stored in an airtight container or Ziploc bag
  • add isopropyl alcohol at the end of bath bomb mixture to reduce risk due to moisture in the air
  • if you are struggling with expansion or breakage issues, try using a bath bomb mold
  • allow the bath bomb to fully dry and then pop it outof the mold
  • gently squeeze and smash it back together with your hands
  • add a bit more citric acid and baking soda mixture to help dry up any excess moisture.
  • Mix the ingredients together well before adding them to your molds or containers. Don’t worry about lumps in your mixture; these will melt out during heating, stirring, or mixing.

Use alcohol in the binder

Using witch hazel or alcohol solution to help reduce the risk of moisture.

Add one drop of glycerin or jojoba oil per tablespoon of aloe vera gel to reduce drying time and enhance moisturizing benefits. Alcohol evaporates quickly and is better to use over water when binding the dry ingredients.

Avoid making them on rainy days or in high humidity.

Don’t over stir the mixture when adding ingredients to your bath bomb mixture. If you live in a wet climate be sure to make these in an air conditioned room, as a humid climate will make them expand. For the drying process put them in the oven and use less oil mix with the dry ingredients.

Keep a small ball of mixture together while stirring instead of trying to mix everything into one big clump. This will help prevent an uneven texture that can cause breakage at times.

Don’t add too much water or alcohol to the mixture either one can cause the mixture to expand. All bath bombs dry in a dry area like the oven. Bath bombs stay in the mold overnight is best.

Don’t allow bath bombs to sit out in air for too long as this can cause them to harden and crack.

Package your product correctly which includes using a thick cello bag and top with an airtight seal and then tape or tie with ribbon. If you choose not to package it, be sure you keep it in a dry, dark space that has a temperature between 60 and 70 degrees Fahrenheit.

Do not use a microwave to heat bath bomb mixture as this can cause it to explode or melt.

Only use molds with rounded edges so the bath bomb doesn’t expand over the side of the mold.

Remove gently from mold by using an upward motion.

Let products dry completely before removing from mold or packaging.

If they feel moist at all, allow them to dry for another day before removing from the mold. Drying time can depend on humidity levels but may take anywhere between 24-72 hours.

Dry the bath bombs in an oven

at 200 degrees Fahrenheit for 20-30 minutes.

Don’t let bath bombs touch one another while drying. Keep a few bath bombs apart when drying or wrap in a paper towel.

Package them When Dry.

Be sure to choose an airtight container for storage or in a plastic wrap.

Bath Bombs are made with sodium bicarbonate, citric acid, cream of tartar, corn starch, Epsom salt, arrowroot powder or kaolin clay, avocado oil or other carrier oil, essential oil, mica.

The best way to store Bath Bombs is in an airtight container away from light and moisture at room temperature. You can also keep them in the refrigerator if they are prone to sweating or melting.

Do not let bath bombs touch one another while drying as this can cause breakage.

Don’t expose bath bombs to direct sunlight as this can cause them to harden and crack. Allow for proper drying time before packaging or using the product.

Too much heat or humidity can cause breakage so be sure they are kept in a dry, dark space with a temperature between 60 and 70 degrees Fahrenheit.

How do you fix expanding bath bombs?

To fix an expanding bath bomb, place it in a microwave safe bowl and heat for 15-20 seconds. Do not overheat the bath bomb mixture as this can cause it to explode or melt. For best results, use a mitt when heating your product.

Can over-expanded bath bombs be recycled?

Can over-expanded bath bombs be recycled?

Yes, to recycle your over expanded bath bombs, simply remelt them by microwaving for 15-20 seconds.

Be sure to use a mitt as they may become very hot. Pour the melted mixture back into the mold and let it sit for an hour or two before removing from the mold.

Take Away on Making Bath Bomb Mixture Expanding

With these tips on how not to make your bath bomb expand too much, hopefully fewer of your bath bombs will have this issue. Check out our other bath bomb questions topics such as what to do if bath bombs sink, or why is my bath bomb crumbly. If you have bath bomb warts of if you have a weak fizzing reaction when you drop in the bath water. A fizz prematurely is down to too much wet ingredients.

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