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Watermelon Bath Bombs by Robyn

As a kid one of my favorite summertime treats was a slice of juicy watermelon. It was messy and fun! Watermelon remains one of the iconic symbols of summer, and I had just created some unique watermelon soaps for the Lovin Soap Blog, so it only seemed right to make watermelon bath bombs too! 

These cute bath treats use a basic bath bomb recipe like this one from Amanda!

Ingredients:

  • Baking Soda – 250 grams
  • Citric Acid – 100 grams
  • Cream of Tartar – 12 g
  • Kaolin Clay – 3 grams
  • Cornstarch – 10 grams
  • Avocado Oil or Cocoa Butter – 5 grams
  • Polysorbate 80 – 5 grams
  • Fragrance Oil – 7 g (I used Sour Watermelon from Natures Garden)
  • FDA approved Lake or Dye color (Red 28, Yellow 5, Blue 1)
  • Mica (white & black)

Equipment

  • Mixing bowl & Hand Mixer OR Stand Mixer
  • Digital Scale
  • Sifter
  • Spatula
  • Face Mask, gloves, head covering
  • Pie Mold from Cada Molds (or any wedge/triangle shaped mold)
  • Small container for mixing mica
  • 3-4 craft paint brushes
  • Towel for covering mixer
  • Spray bottle with binder

There are benefits to using Lakes in bath bombs, and benefits to using Dyes. While I normally go for Lakes, I decided to switch it up today and use Dyes. I pre-hydrate my dyes. It’s an alternative to blooming for the less patient ones of us out there. To do this I add approximately 10 microscoops of powdered Dye to a ½ ounce amber dropper bottle, then fill the dropper with distilled water and label the bottle. When I want to add Dyes instead of Lakes, I have color ready to go. I could add this to my baking soda, but I actually prefer to add it to my liquids, which I’ll show you today.   

NOTE: I live in a very humid environment and like to add my Citric Acid last to help prevent accidental reactivity. If you find that warts and bumps are a problem in your bath bombs, you might try this! I also like to weigh all my ingredients. If you would like to see this same recipe with volumetric measurements, here is a link! https://www.bathfizzandfoam.com/basic-bath-bomb-recipe/

Alright! Get those mask and gloves on and cover that hair, cause its time to make some bath bombs!

Step 1: Weight out all your dry ingredients, except for citric acid. Make sure you’re wearing a mask to prevent the dust from getting onto your lungs! Sift each ingredient as you add it into the bowl to help break up any chunks or lumps. Gently stir all the dry ingredients (except Citric Acid!) together so you have a homogenous mixture. 

Step 2: I like the way Cocoa Butter feels in my bath bombs, so that’s what I chose! Melt it in a microwave safe container, then add all the remaining liquid ingredients. To that I added 10 drops of pre-hydrated Red 27 Dye, and 5 drops of pre-hydrated Yellow 5 dye. Stir well, then add to your dry ingredients.

Step 3: If you’re using a stand mixer I suggest using a paddle attachment. If you’re using a hand mixer go with what you have! Either way, make sure you use a towel to cover the mix until its wet enough to not be airborne! When it’s all nice and blended go ahead and give it 2-3 squirts of your binder and give it another good mix! I use plain water. Some people use witch hazel, others use rubbing alcohol, and Amanda uses a 50/50 blend of Rubbing alcohol and water! Use what works for you! 

Step 4: Add in your citric acid! Make sure it’s nice and incorporated! Give the mix a squeeze and try a drop test. If it’s holding together pretty well even when it’s dropped from a few inches then it’s probably ready to go!

Step 5: I like to weigh my empty mold and tare the scale out to zero so I know exactly how much each bath bomb will weigh, but this isn’t entirely necessary! 

  • Using a 3D printed mold like this Cada Plunger style Mold, place the flat cap piece into the shell then scoop plenty of mix in. 
  • I weighed mine to 4.6 ounces, because they will probably lose a little mix in the pressing and cure, and I’d like the end weight to be 4.5 ounces 
  • Next take the thick plunger piece, fit it into the shell, and press firmly down. You don’t need to smash these down super hard, or kill your wrists! Just firmly and evenly apply pressure. 
  • Give the mold a few told taps with a spoon (or your favorite knocker of choice!) to help it release
  • Flip the mold over and remove the flat cap piece, then gently press the shell down until the bath bomb is out. 
  • I like to place an index card or piece of cardboard on top of the bath bomb as I flip it over to help prevent dramatic, tearful scenes that surely ensure when I smash/drop the darn thing. 
  • Give it one last gentle tap to release the plunger piece and you’re done! Time to make a zillion more!

While this seems like a lot of work, it’s actually really quick and fun once you get going. Sometimes the tips of my wedges crack or pull up, but if you’re gentle, you can generally tap them back in place with little to no cosmetic damage. 

Give your bath bombs  2-3 days to dry before proceeding to the next step!

Most blue and green micas are not approved for use in bath bombs, but there is an easy way around that! Using a white mica like this Winter White from Nurture Soap Supplies, you can add lakes or dyes, then blend with your favorite paint substrate to create the color you need! A paint substrate can be Rubbing Alcohol (my favorite), Polysorbate 80, or even a light oil. It just depends on your preference.

Leaf Green

  • 1 Tbsp of white mica
  • 1 Microscoop of Blue 1 Lake
  • 2 Microscoops of Yellow 5 Dye

Forest Green

  • ¼ tsp of the Leaf green blend
  • 2 Microscoops of Blue 1 Lake

When your green blends are nice and fluid begin by painting the outside rind, top and side edges the lighter, leaf green color.

Add three dark green stripes on the back of the rind, and one on each side.

Use white mica to paint the white strip of rind. Add the finishing touch of the watermelon seeds!

Allow your bath bombs to dry an additional 24 hours before wrapping to help prevent mica smearing! Enjoy these fruity fun summer treats!

We wanted to feature two watermelon bath bombs posted by members of Bath Fizz & Foam. They were just tooooooo adorable!

These first two are by Jennifer Steele: steelesoaps.com

These next two are by Alicia Jordan: www.fizzy.us

About Robyn French Smith

My name is Robyn French Smith! I studied fine art at the University of St Thomas and the Glassell School of Art in Houston TX, and graphic design at The Art Institute of Houston. I started dabbling in DIY bath and body products over 10 years ago after moving to Alaska. While I knew how to make basic soap for several years, I didn’t start looking at it as an art form until about 4 years ago when a neck and shoulder injury made it almost impossible for me to draw and paint. I needed a place for all that creativity to go, and I found it in soap. I received my Basic Soapmaker Certification from the HSCG in 2019 and plan on pursuing further levels of certification.

Find me online at scandaloussoap.com and Facebook!

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