DIY Bath Bomb for Kids – Fun Science Experiments For Kids

It’s amazing how a single ball of chemicals makes bath time so much more fun.

This experiment puts the amazing invention, bath bombs, on center stage. Bath bombs are chemical concoctions that bring together scents and relaxing agents to take bath time to the next level.

For the science fair, you can submit this project under chemistry as it is a simple project seeking to explore what chemicals can affect bath bomb performance. Through a simple experiment, you will be exploring bath balls’ history, the chemicals behind their magic, and the science at work that makes these products the amazing trend it is right now.

What Are Bath Bombs?

Bath bombs are the fist-sized balls or blocks that unleash fizz and aromas as they dissolve in water. These products are called bombs because of the rapid reaction it causes when thrown in bathtubs or small pools. Developers craft these balls with ingredients and components that soothe and relax.

Bath Bomb History

Believe it or not, Bath Bombs have been around since 1989. Lush Cosmetics Co-Founder Mo Constantine and her husband, Mark, explored a curiosity that they had about Alka-seltzer tablets. The original version that Constantine submitted for her patent at the end of the 80s was a compacted mixture of both wet and ingredients that designers molded into unique shapes and dried for durability.

As these initial designs were thrown into the water, the water quickly reacted to the chemicals and fizzed relentlessly, releasing and dispersing ingredients such as essential oils, moisturizers, scents, colorants, and bubbles. It also produces a loud sizzling sound, giving it its original name, the Aqua Sizzlers.

Nowadays, aqua sizzlers have evolved to become bath bombs. The materials and resources that professionals put into their products have become varied and assorted, ranging from all-natural ingredients to highly therapeutic. 

Most bath bombs are available in stores, but thanks to today’s technology, some companies now offer DYI kits.

Bath Bomb Science

Generally speaking, bath bombs are primarily a combination of weak acids and bicarbonate bases. Put it simply, the combination of these elements is unreactive when dry but powerfully reacts when dissolved in water. The dissolving process involves the strong fizzing for which bath bombs are known.

The Fizzing Reaction

The fizzing is an acid-base reaction showing the conversion of citric acid and sodium bicarbonate to sodium citrate and carbon dioxide. In simpler terms, materials like baking soda and citric acid can cause a fizzing reaction. Contact with water and the chemical reactions break the bath bomb apart, releasing the ingredients stored within, such as pigments, essential oils, and skin-conditioning elements.

However, many ingredients vary from bath bombs to bath bombs. Fragrances and dyes are generally the most common components of many bath bombs on the market. Companies include such resources to create the aromatic and therapeutic features for which bath bombs have become popular.

Chemical Reactions

Chemical reactions are the processes where one or more substances interact with each other to create one or more different compounds. Reactants, or the substances that interact during the chemical reaction, work together to produce the product or the result of the process.

During chemical reactions, the process rearranges the atoms of the reactants to form new substances or products. Chemical reactions are an integral part of life itself. Many of today’s products rely on chemical reactions to even be conceived or created. From food to healthcare, chemical reactions are foundational phenomena that make life possible.

Reaction Rate

The reaction rate is defined as the speed at which the chemical reaction occurs or progresses. It is expressed in the concentration of the product formed in a span of time or the concentration of a reactant consumed in a span of time.

Chemical reactions progress differently depending on the reactants, the type of chemical transformation, the temperature, and many other factors. According to Keith Laidler of Brittanica, “In general, reactions in which atoms or ions (electrically charged particles) combine occur very rapidly, while those in which covalent bonds (bonds in which atoms share electrons) are broken are much slower.”

Acids and Bases

In the study of chemistry, all substances are categorized under three major classifications known as acids, bases, and salts or neutral. These classifications are often determined using the pH litmus test. The two are differentiated by the ions they produce in solutions as acids produce H+ ions while bases produce OH-.

Sodium Bicarbonate

This chemical or compound has been mentioned in this article quite a few times. Pretty much one of the most important components of bath bombs, sodium bicarbonate, is a quick-reacting chemical. Most people probably know sodium bicarbonate as an important part of baking soda. Its fast-acting nature makes sodium bicarbonate an important chemical in many of today’s essential chemicals.

Citric Acid

Citric acid, like baking soda, is among the most important components in baking soda. Together, these two chemicals make bath bombs fizz strongly underwater. When these two compounds interact with water, they create a strong fizzing reaction and produce carbon dioxide in the form of bubbles.

Citric acid is an organic compound that is characterized to be colorless and weak as an organic acid. This acid naturally occurs in citrus fruits. People use citric acid as an acidifier, flavoring, and chelating agent, producing over two million tons every year.

Acid-Base Chemical Reaction

An acid-base chemical reaction is a process described as the exchange of one or more hydrogen ions between substances that may be neutral, electrical charged, or carbonate.

The Experiment: How Does Cornstarch Affect Bath Bombs?

For this experiment, you will be assessing how cornstarch affects the fizzing ability of bath bombs. You will be following an experiment that will allow you to test bath bomb fizzing performance with the use of simple resources that can mostly be found at home.

This project is intermediate level, so it will require some effort, time, and knowledge to execute. The experiment will require the use of an oven, so while safe, it is still required to have adult supervision.

The Materials

There are DIY Bath Bomb Kits available online, which you can use for this experiment. This science kit will provide you with all that you need for the creation of your customized bath bomb. However, you’ll still need to search the tool shed for items vital to the experiments, such as measuring cups and other paraphernalia.

The Bath Bomb Science Kit

Buy on: Home Science Tools

You can create your personalized bath bomb with the Bath Bomb Science Kit. You can add in any ingredient you wish and learn all there is to know about the science behind its magic. Alter the ingredients as much as you can to see how it affects their properties.

The package comes with all the ingredients you need to make your own bath bomb experience, including raspberry and vanilla fragrances that you can enjoy. Explore the recipes that work best for you by changing quantities and adding other ingredients you like.

This science kit includes the following: 

  • Six Spherical Bath Bomb Molds
  • Cornstarch
  • Baking Soda
  • Epsom Salt
  • Citric Acid
  • Food colors
  • Fragrance
  • Waterproof thermometer

This science kit comes with a considerably wide array of supplies, including six bath bomb mold and a pound of cornstarch, baking soda, and Epsom salt. The food coloring comes in red, blue, and yellow varieties, and half a pound of each fragrance.

Tools and Instruments

To carry out the experiment, you will need measuring tools and containers for testing. Below are some of the things you need. Most of these items are standard and can be found in an average household. If there’s anything you need, a quick trip to the grocery, pharmacy, and hardware store will do the trick.

  • Four Large bowls
  • Masking tape or painter’s tape
  • Pen or permanent marker
  • Measuring cup
  • Water
  • Vegetable oil
  • Medicine dropper
  • Measuring spoons
  • Forks and spoons for mixing
  • Stopwatch or timer
  • Oven

An oven is optional, but since the weather and humanity may vary from place to place, the oven will be recommended for the drying stage. You may also want to ask for help recording the reaction time during the experiment. Prepare a lab notebook so you can record your findings in an organized way.

Preparing the Bath Bomb Ingredients

Home Science Tools

For this experiment, you will be creating multiple sets of two different recipes. One of the recipes will be the standard combination of all the ingredients, and the second recipe is the one with the added volume on one variable: cornstarch.

Despite a difference in the recipes, the overall measurements of both recipes will be around or close to 16 tbsps. This should be enough to make three bath bomb half spheres. Depending on how many bath bomb kits you buy, you can make more sets for more trials.

Follow the recipes as shown below:

NameRecipe #1 (Normal)Recipe #2 (Extra Cornstarch)
Citric Acid3 tbsp.2 tbsp.
Baking Soda6 tbsp.4 tbsp.
Cornstarch4.5 tbsp.7.5 tbsp.
Epsom Salt1.5 tbsp.1.5 tbsp.
Food Coloring5 drops5 drops
Water2.25 tsp.5.5 tsp.
Vegetable Oil2.25 tsp.2.25 tsp.
Fragrance30 drops30 drops
Approximate Total16.5 tbsp.17.5 tbsp.

Creating the Bath Bombs

With a masking tape and marker, label two different bowls with Recipe #1 and Recipe #2. In the bowls, mix together the ingredients as shown in the table above. Start with citric acid, baking soda, cornstarch, and Epsom salt. Make sure to have separate bowls for Recipe #1 and Recipe #2.

After giving both mixtures a good stir, create two sets of solutions on separate bowls. Add water, the coloring, the vegetable oil, and the fragrances in separate bowls. Add one color into one bowl and a different one to another. Assign different colors for each bowl by choosing from the four different colors manufacturers included in the science kit.

At this point, you will have four separate bowls: two with dry mixed ingredients and two with wet ingredients (the coloring, the fragrance, water, and oil). Use the medicine droppers for the food coloring and the fragrance for precision. Make sure to rinse out the droppers, spoons, and cups as you move from one ingredient to the next.

Mixing the Dry and Wet Ingredients

Make sure you remember which set of dry ingredients goes with the wet ingredients. Before you move forward, it’s important to note that you may not need all of the wet ingredients, as bath bomb-making heavily relies on your environment’s humidity.

Prepare two extra spoons aside from the one you’re using for mixing the ingredients together. Add the wet ingredients to the dry ingredients slowly and in portions. As you add the portions, you may notice the chemicals fizzle. Quickly stop this reaction by pressing the fizzing area with the extra clean spoon (the other extra spoon is for the other bowl). Once the fizz stops, leaving a damp area, mix the ingredients together.

Repeat adding the portions, stopping the fizz, and mixing the damp area until the consistency becomes damp yet powdery. Be careful not to add too much of the wet ingredients because if you add too much of the solution, the fizz will be uncontrollable, and the reaction will continue relentlessly. This will ruin the mixture, and you will have to start over.

Do this process for both the Normal Recipe and the Extra Cornstarch Recipe. If the reaction is too strong, consider lessening the water for your next attempts. If the bath bombs are too crumbly, the mixture might be too dry. If this is the case, you will have to start over but with 3 tsps of water instead.

Shaping the Bath Bombs

Home Science Tools

With a clean dropper, add a drop of vegetable oil into six different haves of the spherical bath bomb molds. Rub the vegetable through the surface of the molds with your finger. This will make the extraction easier when the mixture is dried and ready to be removed.

Move the mixture you prepared for both bowls into the molds a spoonful at a time. As you move a single spoonful into the molds, use the back of the spoon, your palm, or your fingers to press onto the surface and make it as tight and compact as possible. Do this with care to ensure that you fill all the gaps in the mixture and make it hard and solid. Do not fill the molds above the rim. This will give you a hard time removing the bath bombs once they’ve dried.

Once the bath bombs are solid enough, move the bath bomb molds onto a plate so they can dry out. If you feel like the humidity is enough to dry the bath bombs, you may leave them overnight. If you wish to use an oven, you may heat it to 170 F. Once you reach the temperature, immediately turn the oven off and put the bath bombs in the deactivated oven for an hour. 

After your preferred drying process, you may remove the molds, and you can move to the next step. If you feel like the bath bombs are crumbly, you may need to start again.

Testing and Experimentation

Before moving forward with the experiment, prepare a notebook and draw a table similar to the figure below:

TrialTemperature(in °C)Time to Dissolve(in secs)Observations
Recipe #1 (Normal Recipe)1
Recipe #2 (Extra Cornstarch)1

For this experiment, you will be observing the bath bombs fizzing in conditions similar to a bath. Bath water temperatures range from 32C and 43C. As you go through the trial for each bath bomb, record the exact temperature as this affects the output.

If the water is too cold, do not move forward, the temperature must be within the range of the simulation. Remove the water from the bowl and fill it up with hotter water.

Once you set the temperature to the required levels, you may want someone to assist you with the stopwatch. Start from the moment the bath bombs start to show signs of fizzling until it stops. Observe how the bath bomb reacts to the water and record the time in seconds. Make sure to take note of the time and your observations. It may be hard to find out whether or not the bath bomb has stopped fizzling, so you can check with your hands. If you feel the water still fizzling, do not stop the timer and wait for the water to calm down.

Test both the normal recipe and the extra cornstarch recipe using the same conditions but on separate bowls.

Analyzing the Results

Create the visuals for your science fair project using graphs and tables. Draw and present your conclusion using your data and synthesize your findings. Calculate the average time it takes for the bath bombs to dissolve – separating, of course, the results corresponding to the recipes.

Based on your findings, which bath bombs dissolved faster? What does this have to do with reaction rates? How does cornstarch affect bat bombs and the chemical reactions? Explain your conclusions through visual instruments and present your findings.

Elena Jones

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