It’s finally getting warm again here in Calgary, and that means I recently went on my first run of the season. That also means I am very, very sore. And that means it’s time for (more) baths! These lovely Lavender Oat Foaming Bath Salts contain tons of sore-muscle-soothing Epsom salts, while also filling your tub with a rich lather. Lavender essential oil brings a relaxing aromatherapy note, and a touch of dye turns your bath water a very pretty purple. It’s just the thing for a post-run soak!

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The bulk of these bath salts is Epsom salts, aka magnesium sulfate—brilliant for soothing sore muscles, inexpensive, and readily available from places like Costco and your local drug store. I’m a big fan of heavy ingredients being readily available locally so I don’t have to pay to ship myself multiple kilos of things!

I’ve also included two new-to-me ingredients that really help improve bath salts, preventing clumping and improving scent retention. They are dendritic salts and Natrasorb. Both have very unassuming INCIs—sodium chloride and tapioca starch, respectively, so they’re quite unassuming on ingredient labels, but they’re both quite different from plain ol’ table salt and tapioca starch.

Dendritic salt crystals have far more surface area than regular salt and are far more absorbent—this improved absorptive capacity means this special salt holds onto fragrances and other liquids well, helping prevent clumping so your bath salts don’t turn into a bath rock over time. Natrasorb is similarly super-absorbent and also contributes a lovely silky feel to the bathwater. You could easily use one or the other, but I had a lot of fun playing with both.

The fun parts of these salts are the colour, the scent, and the bubbles! I’ve included a tiny amount of water-soluble dye that looks rather subdued in the dry salts but blooms out beautifully in the bathwater. Sodium Lauryl Sulfoacetate (SLSa), a finely powdered anionic surfactant, kicks out a raft of luscious lather when the salts are added to a running bath. And, of course, fragrant lavender essential oil and soothing colloidal oatmeal to round off the entire affair.

We’ll begin by stirring together the dendritic salts, colloidal oatmeal, dye, and Natrasorb, and then massaging in the essential oil and Polysorbate 80. The Epsom salts and Sodium Lauryl Sulfoacetate (SLSa) are added last. Make sure you wear a dust mask when incorporating the surfactant! You’ll leave the salts to dry a wee bit for a couple of days before packaging them up (thanks for the tip, Becky!) to further prevent clumping, and that’s it!

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Lavender Oat Foaming Bath Salts

7.5g | 5% dendritic salt (USA / Canada)
3g | 2% colloidal oatmeal (USA / Canada)
0.015g | 0.01% purple water-soluble dye

6g | 4% Natrasorb (USA / Canada)
0.75g | 0.5% lavender essential oil
1.5g | 1% Polysorbate 80 (USA / Canada)

116.24g | 77.49% Epsom salt (USA / Canada)

15g | 10% Sodium Lauryl Sulfoacetate (SLSa) (USA / Canada)

Weigh the dendritic salt, colloidal oatmeal, and dye into a bowl. Mix together with gloved hands. Add the Natrasorb, essential oil, and Polysorbate 80. Massage everything together with gloved hands until the mixture is uniform.

Add the Epsom salts, and blend until uniform.

Put on your dust mask. Add the Sodium Lauryl Sulfoacetate (SLSa), and gently mix everything together with your hands until uniform.

Spread the mixture out on a cookie sheet and leave it to dry for two days before packaging. I used a pretty apothecary-style jar with a cork top and wooden spoon from YellowBee. To use, add a few tablespoons (or more—it’s up to you!) to a running bath and enjoy the bubbles, scent, and colour!

Because these bath salts do not contain any water, they do not require a broad-spectrum preservative (broad spectrum preservatives ward off microbial growth, and microbes require water to live—no water, no microbes!). Be sure to keep the mixture dry to ensure it lasts as long as possible—don’t let any water get into the container and it should easily last at least year.


As always, be aware that making substitutions will change the final product. While these swaps won’t break the recipe, you will get a different final product than I did.

  • As I’ve provided this recipe in percentages as well as grams you can easily calculate it to any size using a simple spreadsheet as I’ve explained in this post. As written in grams this recipe will make 150g.
  • To learn more about the ingredients used in this recipe, including why they’re included and what you can substitute them with, please visit the Humblebee & Me Encyclopedia. It doesn’t have everything in it yet, but there’s lots of good information there! If I have not given a specific substitution suggestion in this list please look up the ingredient in the encyclopedia before asking.
  • I recommend making sure you have at least one of either dendritic salts or Natrasorb in the bath salts.
    • If you just use dendritic salts I’d replace the Natrasorb with a plain starch, like corn starch, arrowroot starch, or tapioca starch (you could also use more colloidal oatmeal, and in that vein, you could replace the colloidal oatmeal with starch).
    • If you just use Natrasorb, I’d replace the dendritic salts with a different fine salt.
  • You could play with adjusting the salt blend so it’s not just Epsom salts—just be sure to keep things on the fine grain side so you don’t end up sitting on gravel-like chunks of undissolved salt on the bottom of your tub, and keep batches small until you’re sure your blend works well.
  • You could use Polysorbate 20 instead of Polysorbate 80, or read this for other ideas.
  • You can use a different essential oil or fragrance oil.
  • If you’d like to learn more about the surfactant used and compare it to ones you might already have so you can make substitutions, check out this page.
  • I don’t recommend adding whole botanicals to the bath salts as they tend to make a mess in the tub.

Gifting Disclosure

The purple water-soluble dye and frosted plastic jar were gifted by YellowBee.