Black Hole Bath Bomb

Black Hole Bath Bomb Recipe

Do you have a space enthusiast in your life? This Black Hole Bath Bomb Recipe is sure to be a massive hit! It is a fantastic addition to a space or Stephen Hawking unit study, plus making bath bombs is a fantastic chemistry lesson.

ACTIVATED CHARCOAL BLACK HOLE BATH BOMB

A black donut shaped bath bomb sits on a black background. The bath bomb is covered with a ring of orange soap, with a sprinkling of silver stars. Overlay text says Black Hole Bath Bomb Recipe and Science Lesson

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Learning about the lives of famous scientists and STEAMist is always fascinating. Kids can learn so much from the struggles and triumphs of these names they hear so often. In our world the big obsession is space. So when I asked my son to name a scientist he is inspired by, he declared Stephen Hawking before I had barely finished asking the question.

Now if ever there was a brilliant person who overcame incredible odds and still left an amazing legacy, it was Stephen Hawking.

The next thing I asked my son was what parts of Hawking’s work was he most interested in. The answer, Black Holes.

So after reading up on the life and works of Stephen Hawking, we decided we wanted to make a cool little project. The result?

A Black Hole Bath Bomb. Brilliant!!

What Are Black Holes?

A black hole is caused by a dying star that collapses in on itself. This results in such a strong gravitational pull that matter is squeezed into a really tiny space. Nothing can escape a black hole including light. This makes them essentially invisible.

That’s why it was so incredible when scientists were able to photograph a black hole, releasing the image in April 2019.

Take a moment to go look at that picture at NASA. Notice how the black hole has an orange glowing ring? You can also learn more about black holes from NASA here.

Black holes super-heat the material around them and warp spacetime. Material accumulates around black holes which is then heated to billions of degrees and reaches nearly the speed of light. The gravity of the black hole bends the light which creates that glowing photon ring we see in that photo.

Not all is as it seems. The colors of the bright ring in the image aren’t the actual colours in space. They are actually colours chosen by the researchers to depict the density of the emissions. The yellow is the most intense emission, the red is less intense, and then black is little or no emission at all. The black is the black hole.

Read more at National Geographic about Black Holes and this image.

THE SCIENCE OF Black Hole Bath Bombs

Now we have chatted about the astrophysics, let’s chat about bath bomb science. In this project we have some fascinating chemistry.

Bath bombs fizz due to an acid-base reaction. In our recipe the acid is Citric Acid and the base is Sodium Bicarbonate (Baking Soda). While they are in their dry, powder form, you can mix them without causing a reaction, but add some water and they start reacting, releasing CO2 gas (Carbon Dioxide). The gas released is what causes the bubbles and fizz.

Another interesting ingredient in our recipe is polysorbate 80. If you take a look at our ingredients, you will see that oil is used. Oil and water do not mix. So we need to use something to stop all those oils floating in a layer of scummy nastiness on top of the bath water.

The answer is an emulsifier called polysorbate 80. Which is incredibly useful for more than bath bomb making. It made all the difference in our Moon Dough recipe!

Another benefit with an emulsifier is that it helps stop all the colours, oils and activated charcoal from sticking to the bather and the sides of the tub. This helps enormously with clean up after using a bath bomb.

Now, onto making our Black Hole Bath Bombs!

Black Hole Bath Bomb

Black Hole Bath Bomb Ingredients

2 cups baking soda
3/4 cup citric acid
1/4 cup cream of tartar
1 cup cornstarch
1/3 cup coconut oil
2 tablespoons polysorbate 80
10-20 drops each of cardamom and rosemary essential oil
2 tablespoons activated charcoal powder
Black biodegradable cosmetic glitter (optional)
Candy sprinkles star shaped (optional)
1 large mixing bowl
1 small microwave safe measuring cup or bowl
Measuring cups and spoons
Silicone Donut Mold
Melt and Pour Soap (white)
Orange Soap Colouring
Disposable gloves
Parchment paper

Sodium Bicarbonate, Baking Soda, by Pure Organic Ingredients, 2 lb, Highest Purity, Food Grade, Eco-Friendly PackagingCitric Acid (4 oz) by Pure Organic Ingredients, Eco-Friendly Packaging, All-Natural, Highest Quality, Pure, Food Grade, Non-GMOCitric Acid - 1 lb USA Made Pure for Bath Bombs - Gluten Free Kosher No GMO's - Verified for Organic FoodsCream of Tartar (2 lb.) by Pure Organic Ingredients, Eco-Friendly Packaging, All-Natural, Non-GMO, Kosher, for Baking, Cleaning, DIY Bathbombs, MoreAnthony's Organic Cornstarch (2lb), Gluten Free, Vegan & Non-GMOViva Naturals Organic Extra Virgin Coconut Oil, 16 OuncePolysorbate 80 (Solubilser) - 500gOrganic Bulk Activated Charcoal Powder, 2 lb - The Only USDA Certified Organic. Food Grade Powder, Non-GMO, Vegan, No Fillers 100% Pure Use for teeth Whitening Facial Masks DetoxingBiodegradable Glitter Chunky Glitter for Festivals. Eco Friendly Body Glitter for Hair Glitter and Nail Glitter (Violet)3-Pack Silicone Donut Baking Pan of 100% Nonstick Silicone. BPA Free Mold Sheet Tray. Makes Perfect 3 Inch Donuts. Tray Measures 10x7 Inches. Easy Clean, Dishwasher Microwave SafeShea Butter - 2 Lbs Melt and Pour Soap Base - Our Earth's Secrets12 Color Bath Bomb Soap Dye - Skin Safe Bath Bomb Colorant Food Grade Coloring for Soap Making Supplies, Natural Liquid Soap Colorant for DIY Bath Bomb Supplies Kit, Slime, Crafts - with Instructions

 

HOW TO MAKE A BLACK HOLE BATH BOMB

THE BATH BOMB MIX

Cover your table with parchment paper to protect it and make clean up easier. Set out all the supplies.

In the large bowl add baking soda, citric acid, cream of tartar, and cornstarch. Mix with a spoon.

In a microwave safe bowl melt the coconut oil and add the essential oils and polysorbate 80.

Add the liquid mix to the dry mix bowl and mix it all together with your hands. It is completely mixed when it holds a shape when you squish it, just like wet sand.

ACTIVATED CHARCOAL

Add 2 tablespoons of activated charcoal. Use caution, this stuff likes to go everywhere! If you haven’t already put on the disposable gloves, do it now. It will help prevent your hands turning black! Using your gloved hands mix in the activated charcoal really well. Feel free to increase or decrease the activated charcoal amount to suit your taste and the desired colour of the bath bomb.

Tip! Using less activated charcoal will make for a more grey bath bomb, but it will make clean up after bath time a little easier. Activated charcoal is fantastic for oily skin, but if you tend to have more dry skin, reduce the amount of activated charcoal.

Add glitter if desired. Since we are dealing with space we want the glittery stars! We prefer to use a biodegradeable option. Just make sure it is cosmetic grade. Mix.

PACK THE MOLDS

Pack the mixture into the silicone donut molds. Press it in tightly to make sure there are no gaps or cracks. Let harden for 48 hours in a warm, dry place.

After 48 hours, carefully remove the bath bombs from the silicone mold and place on parchment paper.

ADDING THE ORANGE RING TO THE BLACK HOLE

In a microwave safe cup melt 2 or 3 cubes of ‘melt and pour’ soap in the microwave. Use short increments and stir regularly. Once melted add a 4 drops of orange soap colourant and stir.

Ensure your bath bombs are on parchment paper. This next step is a bit messy and if you use something like a plate, they can stick and break. Parchment paper or wax paper is best!

Finally, carefully spoon the soap mixture over your bath bomb. We also tried dipping our bath bombs in the soap mixture. This gives a more even look, but we thought our drizzled soap looked more like the picture of the black hole.

Act quickly with the soap. It will start to get clumpy and harden very quickly.

Let harden for approximately 2 hours. Store in an airtight container until you are ready to use.

Black hole bath bombs on a black background. Black donut shaped bases with orange soap rings on top. 3 bath bombs pictured with text overlay that says Black Hole Bath Bomb Recipe and Science Lesson

MORE HANDS ON DISCOVERY PROJECTS FOR KIDS

Quilled Solar System Model
Skittles Experiment for the Science Fair inspired by Starry Night
Moon Dough Recipe

Black Hole Bath Bomb Recipe

Inspired by the first picture of a Black Hole we created this new Black Hole Bath Bomb

Supplies

  • 2 cups Baking Soda AKA Sodium Bicarbonate
  • 3/4 cup Citric Acid
  • 1/4 cup Cream of Tartar
  • 1 cup Cornstarch
  • 1/3 cup Coconut Oil
  • 2 Tbsp Polysorbate 80
  • 10-20 drops Cardamom and Rosemary essential oil Or substitute your favourite blend
  • 2 Tbsp Activated Charcoal Adjust as desired
  • Black Biodegradable Glitter Optional
  • Star Shaped Decorative Candy Sprinkles Optional
  • 2-3 cubes Melt and Pour Soap Each cube is approximately 1 ounce of soap
  • 2-4 drops Orange Soap Colorant Adjust for desired colour

Instructions

  1. Cover work area with parchment paper and set out supplies.

  2. In the large bowl add baking soda, citric acid, cream of tartar, and cornstarch. Mix with a spoon.

  3. In a microwave safe bowl melt the coconut oil and add the essential oils and polysorbate 80.

  4. Add the liquid mix to the dry mix bowl and mix it all together with your hands. It is completely mixed when it holds a shape when you squish it, just like wet sand.

  5. Add 2 tablespoons of activated charcoal. Mix well with gloved hands. Add glitter and mix.

  6. Pack the mixture into the silicone donut molds. Press it in tightly to make sure there are no gaps or cracks.

  7. Let harden for 48 hours in a warm, dry place.

  8. After 48 hours, carefully remove the bath bombs from the silicone mold and place on parchment paper.

  9. In a microwave safe cup melt 2 or 3 cubes of ‘melt and pour’ soap in the microwave. Use short increments and stir regularly. Once melted add a 4 drops of orange soap colourant and stir.

  10. Carefully spoon the soap mixture over your bath bomb.

  11. Let harden for approximately 2 hours.

  12. Store in an airtight container until you are ready to use.

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