Sodium Cocoyl Isethionate (SCI)

What is Sodium Cocoyl Isethionate? Sodium Cocoyl Isethionate (SCI) is a solid, gentle anionic surfactant made from coconut oil. It is really versatile and lovely, and is considered natural. It is used to create solid cleansers and opaque liquid cleansers.
INCI Sodium Cocoyl Isethionate
Appearance You can buy SCI as a fine powder, a lumpy powder, chips, or noodles/tiny sticks.
Usage rate The CIR has concluded that Sodium Cocoyl Isethionate (SCI) is “safe for use in cosmetic formulations at 50% in rinse-off products and at 17% in leave-on products”. (source)

How much you’ll need in any given formulation depends on a ton of variables. For solid bars I usually start with at least 30% Sodium Cocoyl Isethionate (SCI); for liquid formulations 5–15% is a decent starting point.
Texture It depends on what you buy (see “appearance”).
Scent Characteristically soapy/detergent-y.
Active Surfactant Matter ~84% (always double check with your supplier as this number can vary)

What is the other ~16%? “Sodium cocoyl isethionate may contain the following impurities: … sodium chloride (0.8% max.), free fatty matter (10% max.), sodium isethionate (5%), free fatty acid (18%), and sodium soap (3%).” (source)
pH 4.5– 6.5 (10% Solution)
Charge Anionic
Solubility Sodium Cocoyl Isethionate is water soluble, but not very enthusiastically. Its cousin, Sodium Lauroyl Methyl Isethionate (SLMI), is far more water soluble.
Why do we use it in formulations? It offers beautiful, gentle “lace glove” lather to our products. It’s also naturally acidic, so it helps our end products have a skin-friendly pH with less (or no) adjusting.
Do you need it? It depends on what you want to make! If you primarily want to make shampoo bars and other solid cleansing bars, I highly recommend Sodium Cocoyl Isethionate (SCI).

If you are more interested in foaming bath products (bath salts, bath bombs, bath truffles, etc.), I’d probably choose Sodium Lauryl Sulfoacetate (SLSa) over Sodium Cocoyl Isethionate (SCI) as it’s far more water soluble.

If your primary aim to create liquid surfactant products, I’d choose liquid surfactants and/or solid surfactants that are more water soluble (Sodium Coco Sulfate [SCS], Sodium Lauroyl Methyl Isethionate [SLMI]) that Sodium Cocoyl Isethionate (SCI) is.
Strengths Wonderful, gentle lather.
Weaknesses The larger shapes can be a pain to melt down.

Sodium Cocoyl Isethionate (SCI) can hydrolyze if it’s in a hydrous (liquid) formulation with a pH below 6, causing formulations to become unstable.
Alternatives & Substitutions As a bare minimum you’ll need a different solid anionic surfactant. You’ll also need to watch the active surfactant matter (you may need to use a different quantity of the new surfactant to get the same ASM level in the end product) and the pH of the final product. Keep in mind that most solid anionic surfactants are not as gentle as SCI. Two options to consider would be SLSa and Sodium (C14-16) olefin sulfonate (Bio-Terge AS90).
How to Work with It Wear a dust mask! Inhaling airborne powdered surfactants is unbelievably unpleasant.

If you’re making a solid product you can usually work with the SCI as-is, depending on the format. If you’ve got large flakes and the formulation calls for the powdered version you’ll want to pre-grind it (wear your dust mask!), but the little noodles look really cool in shampoo bars as-is, and the fine powder is very flexible!

If you are making a liquid product with Sodium Cocoyl Isethionate (SCI), it will need to be dissolved in a suitable solvent first. Sodium Cocoyl Isethionate (SCI) does not dissolve readily into water; I once combined some Sodium Cocoyl Isethionate (SCI) with water in a jar, sealed it, and left it for 6 months. It never dissolved. I recommend combining it with the liquid amphoteric surfactant that is likely also present in the recipe and heating the two together in a water bath until you have a uniform paste. That paste will dissolve into water.

If you are working with a large amount of this Sodium Cocoyl Isethionate (SCI) + amphoteric surfactant blend you can speed things along by using an immersion blender to get the mixture silky smooth—the low water content means it won’t lather up, but you’ll get a smooth paste very quickly! You can also speed up the process by running your SCI through a coffee grinder before combining it with the liquid amphoteric surfactant—just be sure you are wearing your dust mask!

Hydrous formulations including Sodium Cocoyl Isethionate (SCI) should have a pH of 6–8 or the Sodium Cocoyl Isethionate (SCI) can hydrolyze. That said, I have made more acidic formulations featuring Sodium Cocoyl Isethionate (SCI) and haven’t had troubles—though those batches would’ve been quite small and the products were finished quickly.
Storage & Shelf Life Stored somewhere cool, dark, and dry, SCI should last for at least two years.
Tips, Tricks, and Quirks I like to pre-prepare a paste of SCI and Cocamidopropyl Betaine (2 parts SCI to 3 parts Cocamidopropyl Betaine) and store it in the fridge. That way I can skip the dissolving step when I need to include Sodium Cocoyl Isethionate (SCI) in a liquid product.

Watch for SCI that has been blended with stearic acid (INCI will list stearic acid); that isn’t the same product.
Recommended starter amount 250g (0.5lb)
Where to Buy it  Buy it from an online DIY ingredient supplier or Amazon.

Want to compare different surfactants?

Check out my super-useful surfactants table!

 

Some Formulations that Use Sodium Cocoyl Isethionate

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Posted on

November 22, 2018