A little bath bomb help? Not fully hardening?

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Stindall

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Hi everyone! I’ve taken to making bath bombs because my toddler loves them and they’re not cheap lol. Plus I’ve never been great at crafts and this is one thing I feel like I’m having fun with and haven’t been too bad at…except that they seem to only be getting like 95% hard (that’s what she said?). Here’s my recipe and my round molds are about 4.5oz so I’m getting about 5 bombs from this give or take. I live in Northern California and we do have some humidity this time of year.

Dry ingredients
-7 ounces baking soda
-3 ounces citric acid
-4 ounces Epsom salts
-6 ounces of corn starch
-1 teaspoon Mica powder

Wet ingredients
-15 drops fragrance oil
-2 tablespoons of Sunflower oil
-1 tablespoon polysorbate 80
-1 tablespoon of water

When it’s mixed it seems like the perfect “wet sand” consistency. Then after I mold them, I remove them and let them air dry on some parchment.

any idea what I can do to make them set completely other than using the oven? I tried that the first time and they cracked and flattened. I know they’re just for my son but I am a perfectionist. I would like to not have to purchase anything else at this time. I do have a little bit of Kaolin clay I haven’t tried out yet because I’m unsure if I need to change the recipe or if it’s humidity or what.
 
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I would suggest avoiding the water, and substituting the sunflower oil with cocoa butter. Those were the suggestions from a book for a high humidity area, it also called for cream of tartar.
Just in case, (and nothing to do with the hardening) make sure your mica is safe for use in bath bombs. Most blues and greens, and some purples are not (because of the ultramarine pigment in them).
 

Stindall

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I would suggest avoiding the water, and substituting the sunflower oil with cocoa butter. Those were the suggestions from a book for a high humidity area, it also called for cream of tartar.
Just in case, (and nothing to do with the hardening) make sure your mica is safe for use in bath bombs. Most blues and greens, and some purples are not (because of the ultramarine pigment in them).

My micas are from Brambleberry and listed as safe for bath bombs. I’d like to eventually like to try the other types of colorants but they're a little daunting!

I'll try my next batch with less/no water and see how we go. I was reading about adding cream or tartar or Kaolin clay so since I already have the clay I'll give it ago. Thanks for your suggestions!

update: we did try no water but they mold halves would not hold together so we did just 1tsp.
 
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My micas are from Brambleberry and listed as safe for bath bombs. I’d like to eventually like to try the other types of colorants but they're a little daunting!

I'll try my next batch with less/no water and see how we go. I was reading about adding cream or tartar or Kaolin clay so since I already have the clay I'll give it ago. Thanks for your suggestions!

update: we did try no water but they mold halves would not hold together so we did just 1tsp.
I forgot to add, I don’t add any water to my recipe but I do use isopropyl alcohol in a spray bottle to moisten the mix before molding). While micas color the bathbomb itself, a bath-bomb dye will also color the water, which your son might enjoy to see.
 
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I struggled with bathbombs forever. I then found Cada’s recipe. I have not had a problem since. They are in Fl as am I so I knew they had to have the humidity issue I have.
The only thing I do differently is I lowered the SLSA amount. They seemed too foamy to me…like not enough fizz. Water seems to work better for me than alcohol or witch hazel. They dry rock hard within hours.
 
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I also use a modified recipe based on the Cada Molds recipe. I can’t keep bombs in stock and my kid loves them as well. I use 76 coconut oil instead of a liquid oil because i find it helps keep the bomb together when it all solidifies. I also lowered the SLSa and add just a bit of Pibk Himalayan salt for color.
 

scmorgans

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Great info everyone! I'm just now starting to make bath bombs. I'm in the Northeast (Vermont) so not a ton of humidity here. Made one batch using Cada molds...... had some luck but not 100%. I think my mix was drying out on me. This will take some time to learn! I did have luck with the steamer recipe except - Yikes! - go light on the menthol crystals!
 

Complexions

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Hardeners like kaolin clay and cream of tartar are all good suggestions. Also, I would remove the epsom salt. It's generally not enough in a single bomb to make a therapeutic difference, and it's hydroscopic, meaning it will draw moisture from the air, thus causing your bombs to never fully dry out in a humid environment.
 
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