These sparkly, sudsy shampoo bars feature two trending all-natural ingredients with long histories in hair care: castor oil and rice. These inexpensive ingredients are said to help strengthen the hair, boost growth, and improve hair health, so including them in a shampoo bar felt like a no-brainer.

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The dry phase

There are four ingredients in the dry phase of these shampoo bars.

The rice goodness comes from fine, smooth rice flour. Rice water hair rinses have a long history of use in Asia, and are loved by many today as a way to boost hair strength and growth. Rice water is easy enough to make—simply soak some rice in water, strain, and then use that rice-infused water to rinse your hair. The trick is in remembering to do this before your shower, and remembering to take the rice water into the shower with you… two things I do not excel at.

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So, instead: rice flour. A shampoo bar with rice flour isn’t the same thing as a rice water rinse, but it’s got the same component ingredients (rice, and water from your shower) and requires far less thinking ahead.

For the cleansing power,  I’m using a blend of two of my favourite sulfate-free surfactants: Sodium Cocoyl Isethionate (SCI) and Sodium Lauryl Sulfoacetate (SLSa). They create gorgeous dense, velvety lather—I’m a big fan. You’ll need the finely powdered versions of both for these bars (if what you have isn’t finely powdered you can powder if yourself by running it through your DIY-only coffee grinder).

And lastly, a bit of citric acid pulls the pH down to a good-for-the-hair level.

The wet phase

The wet phase is what turns all those powders in the dry phase into a workable, shape-able dough.

Cocamidopropyl Betaine, a mild amphoteric surfactant, rounds out the surfactant blend, make the finished shampoo milder, and boost the bubbles. It also introduces a decent bit of water to the formulation (which is crucial for fusing the bars together as they dry) as Cocamidopropyl Betaine is ~70% water.

Two of the wet phase ingredients were inspired by the live ingredient list analysis session we did over on Patreon for the Kitsch Castor Oil Shampoo & Conditioner Bars back in October 2024.

Castor oil is obvious—no sleuthing required, it’s right in the name! This rich oil is really trending in haircare right now, but it’s certainly not a new haircare ingredient. It’s probably a stretch to say it’ll boost hair growth in a rinse-off product, but it does help make the shampoo gentler and easier on your hair, and there’s some undeniable label appeal, too!

The other ingredient was a bit less obvious; I was intrigued by the blend of strengthening hydrolyzed quinoa, shine-amplifying panthenol, moisturizing hyaluronic acid, and density-boosting pea extract in the castor oil conditioner bar. It turns out those ingredients are all part of an ingredient called Fision HydraTress, and I happened to have some, so I had to include it in this shampoo bar! If you don’t have HydraTress you can replace it with 2% powdered panthenol and 3% of a liquid hydrolyzed protein (oat, rice, baobab, quinoa).

As I find castor oil is quite prone to going rancid, I included some vitamin E along with the preservative. I selected Optiphen™ Plus as the preservative for these bars, but you could switch to a different preservative if you wanted to. Check out this table for some ideas.

And lastly, some fragrance or essential oil makes the bars smell divine. I used Unbroken from Stock Fragrance because I’m obsessed with how it smells both fresh and juicy (though not really fruity, if that makes sense?). It’s also 92.8% biodegradable, petrochemical & phthalate free, and “Clean at Sephora” compliant, which I think is pretty neat. You can, of course, use something else if you prefer; just be sure it’s approved for use at 1% in IFRA category 7A products.

Equipment you’ll need

If you’ve done much making, you probably already have most of the equipment you’ll need:

• A digital scale
• A bowl that’s large enough to mix everything together (one from the kitchen is fine)
• Some spoons (for scooping out ingredients and stirring—kitchen spoons are fine)
• Some smaller bowls to weigh ingredients into (custard cup sized is great)
• A pair of nitrile or latex gloves—so you can really get in there and squish stuff together
• A tight-fitting respirator that seals well on your face so you don’t choke on the floaty surfactants
• Optional: a press (hand or otherwise) or hard-sided cavity mould to shape the bars (they can also be hand shaped)

And a final optional thing that is technically an ingredient, but doesn’t come into things until the very end of the making process—a bit of gold biodegradable glitter to decorate the bars with.

How long do these bars need to dry?

These bars will be noticeably harder within 12 hours, but I’d give them a good 3–4 days to dry out as much as possible before getting them wet again. If you need to gift them before then that’s fine (they get sturdy enough to handle quite quickly), just let your recipient know they need to wait a day or two before trying it out for the first time.

Learn more: How long do you have to age a shampoo bar?

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Relevant links & further reading

• Sodium Cocoyl Isethionate (SCI) in the Humblebee & Me Encyclopedia
• Sodium Lauryl Sulfoacetate (SLSa) in the Humblebee & Me Encyclopedia
• Citric Acid in the Humblebee & Me Encyclopedia
• Castor Oil in the Humblebee & Me Encyclopedia
• Tocopherol (Vitamin E) in the Humblebee & Me Encyclopedia
• Cocamidopropyl Betaine in the Humblebee & Me Encyclopedia
• Optiphen™ Plus in the Humblebee & Me Encyclopedia
• How long will ______ last? What is its shelf life? in the Humblebee & Me FAQ
• How long do you have to age a shampoo bar?
• Can I use a different preservative than the one you’ve used? in the Humblebee & Me FAQ
• pH
  • pH meter in the Humblebee & Me Encyclopedia
  • pH measurement in cosmetic lab: why we dilute samples? from Skin Chakra
  • How to adjust the pH of your cosmetic products from Skin Chakra
  • Why do you create a 10% dilution of a formulation before measuring the pH? in the Humblebee & Me FAQ
• Other shampoo bar formulations:
  • Simple Sulfate-Free Shampoo Bar
  • Champagne Shampoo Bars
  • Sulfate-Free Shampoo Bar with Rice Starch
  • French Green Clay Sulphate-Free Shampoo Bar
  • White Chocolate Peppermint Shampoo Bars

Castor & Rice Sulfate-Free Shampoo Bar

Dry phase
51.75g | 17.25% ultra fine rice flour (USA / Canada)
105g | 35% Sodium Cocoyl Isethionate (SCI) (USA / Canada / UK / Aus / New Zealand / Nigeria)
75g | 25% Sodium Lauryl Sulfoacetate (SLSa) (USA / Canada)
0.75g | 0.25% citric acid (USA / Canada)

Wet phase
15g | 5% Fision® HydraTress (USA / Canada / Greece)
14.7g | 4.9% castor oil (USA / Canada)
0.3g | 0.1% Vitamin E MT-50 (USA / Canada)
31.5g | 10.5% Cocamidopropyl Betaine (USA / Canada)
3g | 1% Optiphen™ Plus (USA / Canada)
3g | 1% fragrance

To decorate: gold biodegradable glitter (optional)

Put on your dust mask (USA / Canada) and weigh the dry phase into a bowl. Stir until uniform.

Add the wet phase to the dry phase. Put on a pair of nitrile gloves and blend thoroughly with your hands. Once the mixture is uniform, you’ll be left with a stiff, easily-mouldable paste.

If your dough is too sticky, you’ll need to add more rice flour. If your dough is too dry, you’ll need to add a little bit of distilled water.

Now it’s time to shape or press the bar! I used a small hand mould from YellowBee, lining the top and bottom with rounds of parchment paper. I sprinkled the top and bottom of the mould with a bit of gold biodegradable glitter before pressing for the “gold & white” theme. Please watch the video to see this in action. You can also use a powered press like The Bath Bomb Press, a hard-sided cavity mould (a measuring cup works nicely!), or simply hand shape the bars.

Carefully un-mold the bars and leave them to dry for at least 3–4 days before using.

To use, massage the bar into wet hair (or a wet loofah, for body washing) to work up a rich lather. From there on out it’s just like using any other shampoo or body wash. Enjoy!

When made as written, the pH of these shampoo bars comes out to around 4.8, which is great.

Shelf Life & Storage

Because these shampoo bars will regularly come into contact with water, I recommend including a broad-spectrum preservative to ward off microbial growth. These bars should easily last 6 months in the shower; I’ve never had a shampoo bar spoil on me, and I’ve had several live in my shower for over a year.

Substitutions

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

• As I’ve provided this formulation 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 formulation will make 300g. You can divide this into as many bars as you want; I made five 60g bars.
• To learn more about the ingredients used in this formulation, 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.
• The wet/dry balance of this formula is really important; if you change anything (especially any of the three ingredients in the dry phase) you may need to re-develop the formulation to get a workable dough.
• If you change any of the ingredients—though especially the surfactants—this will change the pH of the bar. This means you should start with a 20g batch. Test the pH, see where it lands, incorporate more (or less) citric acid, and make a new 20g batch. Once the pH is right you can scale the formulation up and make a larger batch.
• You can try a different starch, but you will likely have to re-work the formulation to get the liquid-to-dry ratio just right.
• If you’d like to learn more about the surfactants used and compare them to ones you might already have so you can make substitutions, check out this page and read this FAQ.
  • I’d recommend Sodium C14-16 Olefin Sulfonate (Bio-Terge® AS-90) instead of the Sodium Lauryl Sulfoacetate (SLSa). Sodium C14-16 Olefin Sulfonate is a solid surfactant; do not confuse it for Sodium (C14-16) alpha olefin sulfonate (Bio-Terge AS40), which is a liquid.
  • Remember that the maximum usage level for Sodium Cocoyl Isethionate (SCI) is 50% for rinse-off products, so you cannot use just Sodium Cocoyl Isethionate (SCI) in this formulation.
• You can replace the Hydratress with 2% powdered panthenol and 3% of a liquid hydrolyzed protein (oat, rice, baobab, quinoa).
• You can substitute the castor oil with a different oil your hair loves—nothing is terribly similar to castor oil, so just choose something you like.
• You can use a different liquid surfactant instead of Cocamidopropyl Betaine; I’d recommend an anionic one, but non-ionic will also work. Options include Sodium Cocoamphoacetate, Decyl Glucoside, Coco Glucoside, and Caprylyl/Capryl Glucoside.
• If you’re like to use a different preservative, please review this FAQ and this chart. This bar is pretty easy to preserve, so I’d feel pretty comfortable using a different preservative assuming it doesn’t have any direct conflicts with the formulation.
• If you’d like to incorporate an essential oil, please read this.
• You can use a different fragrance oil or essential oil if you want to, just be sure its usage rate for IFRA category 9A formulations is 1% (the amount used in this formulation) or higher.