6 reasons why your DIY bath bombs are expanding


Making bath bombs can be a very exciting project; it doesn’t matter if you are new at crafting or a veteran. However, just like with any craft, you need the practice to get everything right. One of the biggest problems one encounters when crafting bath bombs is overexpanding bath bombs, and today we will discuss why this happens.

Your bath bomb has a fizzing reaction prematurely because it has too much water in them. You may have used too much water in your mixture, or it may happen due to moisture in the air. This can also occur because of the fragrance or colorant used in the recipe, which contains water, and this makes the bath bomb too wet.

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.

Making bath bombs is actually quite simple, with just baking soda and citric acid and a little water (or oils) you are done if you are not adding anything extra such as fragrance or colorants. Once you have those three ingredients mixed you get this moldable mixture that feels like wet sand.

This sounds easy and in sense it really is, but the moment you add anything extra like a colorant or fragrance things can get a little tricky and you may end up with too much water in your mixture and as a result, you get overexpanding bath bombs. However this is not the only cause, the place you are leaving your bath bombs to dry or simply a slight faulty measurement may cause this same effect.

Why is my bath bomb expanding?

When the combination of citric acid and baking soda comes into contact with water, it creates the fizzing reaction which you want when you throw your bath bomb in the tub. But when there is too much water in it, this may happen prematurely. This is also known as expanding bath bombs, it starts to fizz, and thus it expands.

Here is a list of reasons why you bath bombs may expand.

1. Moisture in the air

If you never made any bath bombs, you most likely didn’t know that humidity is your number one enemy. If you live in a humid area, you might have a much harder time compared to someone who is living in a dry area.

You see, moisture in the air causes the drying process to slow down or even stop entirely. So it is crucial to have a room that is humid free if you wish to dry your bath bombs correctly. Further down the article, I will mention how to solve this problem.

2. Salt

If your recipe contains salt, you might want to consider taking it out. Your bath bomb might end up with a moisture-dotted surface after a few minutes of exposure. Since salt is hygroscopic, it causes your bath bombs to absorb the moisture in the air. And once that happens, the baking soda and citric acid will activate, and you’ll end up with a failed batch.

3. Fragrance

Using a fragrance is essential when making your bath bombs. Without fragrance, what is the point in making them right? Well, depending on the type of fragrance you are using, they may cause your bath bomb mixture to fizz. It is the water within the fragrance that causes the fizzing reaction in your bath bomb.

If this happens, you may still have some fizzing left if you throw it in the tub, but it would be significantly less than the normal. To be able to avoid this, you need to have a calculator to make sure the ingredients and measurements are well balanced. 

Here is a calculator you can use, just make sure to select “salts” as the option. Then put the correct amount precisely of the mixture you are trying to make (this means all ingredients you want to add). And finally, choose the fragrance you want to add, and the calculator will tell you how much you need to use.

This is the only way to avoid having too much fragrance (water). Just a quick tip: this calculator uses weight measurements, and if your recipe is using volume as measurement, using your nose might be one solution to this. So when you add fragrance, smell it, and if you wish to have a stronger scent add a little more. 

4. Colorants

If you want heavy colors, the amount of colorant is not really important as long it is the right type. However, you’ll need to be careful if you use too much of it, as it may leave traces of color on your tub or even your skin. If you use the wrong type well, this may cause your bath bomb to expand out of the mold. 

You can solve this by using the right type of colorant such as La bomba colorants that are specially made for coloring bath bombs. Compared to other dyes, this one is made with glycerin, while the others are made with water. So with this type, there is no chance your bath bomb will start to fizz. 

5. Too much water

Well, this is maybe a no-brainer, but yes, you may have too much water in your mixture. The easiest way to avoid this is by using a calculator, of course. But it is not only water that can be used. You can use witch hazel or oils, which also can give you the moldable mixture you are trying to achieve.

So if you are planning on using oils anyway, you might not even need water. Some might go for a mix of two, such as isopropyl alcohol and water. But this is a personal preference, or you might have an allergic reaction to any of the ingredients mentioned so you can change it a little.

Just make sure to use the calculator before doing anything, believe me, it will help you avoid getting frustrated with failed batches, and you wouldn’t even know why. 

6. Water in the mold

When you clean, you need to clean thoroughly. I know I sound a little strict, but unfortunately, it needs to be. If you leave just enough water in your molds, you may end up with your bath bombs prematurely starting to fizz. You won’t notice it right away but only when it’s too late, so for me, it’s easy, wipes till you are sure it’s nice and clean and dry.

How do you keep bath bombs from expanding?

  1. Do not make bath bombs on rainy days: If it rains, there is much more humidity in the air, and this also means inside your workplace. So, avoid at all costs doing anything on rainy days, or else you might end up pulling your hair out in no time!
  2. Use a dehumidifier: If you can afford a dehumidifier, I’d say go for it. This is especially helpful if you live in a very humid area. Just a word of caution, if it rains and you live on top of that in a humid area, the results may vary depending on the room size.
  3. Oven dry bath bombs: An easy yet very effective way to solve your humidity problem is to dry your bath bombs in the oven. This is especially good for when you send a batch the same day and need to get things done quickly.

    It is also the cheapest way to solve the humidity problem. Since everyone has an oven in the house, you do not need to invest in a dehumidifier. Put the oven on, warm, and dry your bath bombs for about 1 to 4 hours.
  4. Avoiding July and August months: If you live in the midwest, July and August can be very humid. So you might want to avoid those months altogether. If you insist on making them anyway, you might solve your problem by drying them in the oven or using a dehumidifier, but there is no guarantee it will work.
  5. Using an Air conditioner: In some areas, an air conditioner may also help speed up the process or help with humidity in the air. But this is only the case if you live in an area that is not too humid. You might need to use a fan to help in some cases, but many succeed just with an a/c.
  6. Use a fan: It is the same as the air conditioner; a fan can help with the room’s airflow, which helps to eliminate the air humidity. However, also similar to the air conditioning solution, this only works if you live in a not-so-humid area.
  7. Add hardeners: Using hardeners helps with drying your bath bombs and helps with the speed it dries. However, it may have some drawbacks. Using hardeners may affect the density of your bath bombs. If you are using a lot of kaolin clay, for example, your bath bomb might sink. So if you are planning on using hardeners, make sure to calculate and weigh that into your equation.
  8. Use alcohol in your binder: Binding with alcohol might be one of the ways to help avoid expanding bath bombs. This is because alcohol evaporates very quickly and leases only a hard bomb behind which you can package straight away.

    This does not mean you need to use 100% alcohol, but a blend of 50% alcohol and 50% water seems to do the trick, and the final product is a super-hard bath bomb. In case you wish to use 91% alcohol without adding any water, you might end up with a powdery result because the alcohol was not able to wet the mixture to get the hard bomb.
  9. Package it as soon as you can: The sooner you can package, the better. If you leave them too long out in the open, they may eventually start pulling moisture from the air. When packaging makes sure it is airtight, an excellent way to do this is to use shrinkwrap, or in case you have it available, an airtight container (until you can shrinkwrap).

    In case you want to use any other method, make sure that it is airtight, or else (in case you are selling), your clients will have a nasty surprise when they open their order.

Can over-expanded bath bombs be recycled?

This is impossible, as the mixture would be already dried, and making it wet again is not possible. If you add a little water to it, which means it will have too much water, it will start to fizz.

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