Sodium cocoyl isethionate (SCI) is one of the best ingredients for making modern shampoo bars. It is a mild, sulfate-free, coconut-derived anionic surfactant that comes as a solid powder, flakes, or noodles, and it produces a creamy, dense lather without the high pH and “transition period” associated with traditional lye-based soap bars.

What Makes SCI Different from Soap?

SCI is a syndet, or synthetic detergent. Unlike cold-process or hot-process soap, it does not require lye and does not need a 4-6 week cure. However, it also does not melt like soap. SCI stays solid during processing, so you mix it into melted fatty ingredients rather than melting it directly. Keeping the temperature low is important: excessive heat can damage SCI and make the bar harder to work with.

Basic Shampoo Bar Formula with SCI

This is a balanced starting formula for a 100 g test batch. Scale it up by multiplying each gram amount by the same factor.

  • 60 g SCI powder - primary cleanser and hard bar former
  • 10 g cetearyl alcohol - hardens the bar and adds slip
  • 10 g shea butter - adds emollience and reduces brittleness
  • 5 g BTMS-25 - conditioning emulsifier that improves wet combing
  • 5 g cocamidopropyl betaine - boosts mildness and lather
  • 5 g glycerin - helps the bar hold together and draws moisture to hair
  • 1 g panthenol - optional conditioning additive
  • 3 g fragrance or essential oil - use skin-safe amount for wash-off products
  • 1 g broad-spectrum preservative - needed because cocamidopropyl betaine contains water

Ingredient Notes

  • If your SCI is in noodle or flake form, grind it to a fine powder in a clean coffee grinder before weighing. Fine powder gives a smoother bar.
  • If you want a completely anhydrous version, replace the cocamidopropyl betaine with 5 g of a powdered mild surfactant such as sodium lauryl sulfoacetate, and omit the preservative.
  • For a firmer bar, increase SCI to 65-70% and reduce shea butter or glycerin slightly.

Step-by-Step Instructions

  1. Prepare your workspace. Sanitize tools and molds. Wear a dust mask when handling SCI powder because fine surfactant dust is irritating to airways.
  2. Grind the SCI. If using noodles or flakes, grind them into a fine powder before use.
  3. Melt the fatty ingredients. In a double boiler, gently melt the cetearyl alcohol, shea butter, and BTMS-25 together. Keep the temperature around 65-75°C and do not overheat.
  4. Remove from heat. Stir in the glycerin and cocamidopropyl betaine until the mixture is uniform.
  5. Add the SCI gradually. Sift or sprinkle the SCI powder into the warm mixture while folding with a spatula. The mixture will thicken into a paste or dough. If it becomes too crumbly, add a few drops of warm distilled water or additional glycerin, but keep any added water to a minimum.
  6. Cool before adding heat-sensitive ingredients. Let the mixture cool to below about 40°C, then add fragrance, essential oil, panthenol, and preservative. Stir thoroughly.
  7. Mold the bars. Pack the mixture firmly into silicone molds, pressing well to eliminate air pockets. Silicone molds work best because the bars release easily.
  8. Cool and unmold. Leave the bars at room temperature for 12-24 hours before unmolding.
  9. Dry the bars. Place the unmolded bars on a rack in a cool, dry area for 3-7 days to harden and allow any surface moisture to evaporate.
  10. Check the pH. Dissolve 1 g of bar in 10 ml distilled water. A good shampoo bar should test around pH 5.0-6.0. SCI-based bars usually fall in this range without adjustment.

Troubleshooting and Formulation Tips

  • Too soft or sticky: Increase SCI or cetearyl alcohol by 5-10%, reduce glycerin, and allow a longer drying time.
  • Too brittle or crumbly: Add a little more shea butter or glycerin, or include 2-3% cetyl alcohol as an extra binder.
  • Not enough lather: Replace 5-10% of the SCI with sodium lauryl sulfoacetate or add 2-5% more cocamidopropyl betaine.
  • Too drying: Reduce SCI to 50-55% and increase shea butter or BTMS-25 slightly.
  • For oily hair: Use up to 70% SCI, keep butters low, and consider adding 1-2% kaolin or bentonite clay.
  • Fragrance: Add fragrance below 40°C to avoid evaporation. Some essential oils can accelerate thickening, so work quickly once added.

Preservative and Water Safety

SCI shampoo bars are usually made without water, which means they do not require a preservative in an anhydrous formulation. However, liquid ingredients like cocamidopropyl betaine, aloe vera juice, or hydrosols introduce water into the product. If your formula contains any water-containing ingredient, include a broad-spectrum preservative at the supplier’s recommended usage rate.

With the right balance of SCI, fatty binders, and mild additives, you can create a hard, long-lasting shampoo bar that cleanses gently and rinses cleanly without feeling waxy or stripped.