Yes, you can make a solid shampoo bar with decyl glucoside, but it cannot be the main solidifying ingredient because it is a liquid surfactant. In a shampoo bar, decyl glucoside works best as a secondary surfactant - it adds mildness, improves creaminess, and supports lather when combined with a powdered solid cleanser such as sodium cocoyl isethionate (SCI).

What decyl glucoside adds to a shampoo bar

Decyl glucoside is a mild, plant-derived nonionic surfactant. It is popular in shampoo bars because it helps reduce the potential irritation of stronger anionic surfactants and produces a soft, creamy lather. However, it is not a powder or solid, so it must be balanced with hard, solid ingredients or the bar will stay too soft and melt quickly.

  • Mildness: Gentle on the scalp and hair.
  • Lather support: Boosts foam quality when used with SCI or SLSa.
  • Texture: Softens the bar, so keep usage moderate.
  • pH: Decyl glucoside is naturally alkaline, so pH adjustment is usually needed.

Basic solid shampoo bar formula

This makes a 100 g test batch. You can scale it up once you are happy with the hardness and lather.

  • 45 g Sodium Cocoyl Isethionate (SCI) - primary solid cleanser
  • 15 g Sodium Lauryl Sulfoacetate (SLSa) - optional, for extra lather
  • 10 g Decyl Glucoside - mild liquid secondary surfactant
  • 12 g Cetearyl Alcohol - hardener and emollient
  • 10 g Shea Butter or Cocoa Butter - conditioning and hardness
  • 5 g Glycerin - humectant, but too much softens the bar
  • 1 g Hydrolyzed protein - optional conditioning additive
  • 1 g Fragrance or essential oil
  • 1 g Broad-spectrum preservative
  • Citric acid solution - as needed for pH adjustment

If you omit SLSa, replace it with additional SCI. Keep total liquid ingredients, including decyl glucoside and glycerin, around 20-25% of the formula so the bar remains solid.

Step-by-step method

  1. Prepare your work area. Sanitize equipment, gloves, scale, and molds. Silicone molds work best for shampoo bars.
  2. Melt the hard ingredients. In a double boiler over low heat, melt the cetearyl alcohol and shea or cocoa butter until fully liquid, around 70°C. Do not overheat.
  3. Add the powdered surfactants. Remove from heat and stir in the SCI and SLSa a little at a time. The mixture will become a thick paste or dough. If it stiffens too much, place it back over the warm water briefly.
  4. Add the liquid surfactants. While the mixture is still warm but not very hot, stir in the decyl glucoside and glycerin, plus any water-soluble actives such as hydrolyzed protein. The texture will become softer and stickier - this is normal.
  5. Adjust the pH. Decyl glucoside is alkaline, so check the pH correctly. Dissolve 1 g of the mixture in 9 g of distilled water, then test the solution with a pH strip or meter. Target pH is about 5.0-6.0. Add a 10% citric acid solution dropwise, mixing well and retesting until the target is reached.
  6. Add preservative and fragrance. Stir in the preservative and fragrance or essential oil thoroughly. Do this after pH adjustment.
  7. Mold the bars. Pack the warm paste firmly into silicone molds or shape by hand once cool enough to handle. Press down hard to remove air pockets.
  8. Cool and dry. Let the bars harden at room temperature for 2-4 hours, then unmold. Allow them to dry for 24-48 hours before use. This is not a lye soap cure; it simply lets the bars firm up.

Preservative and pH notes

Because decyl glucoside contains water, this type of shampoo bar is not fully anhydrous. Always include a broad-spectrum preservative at the supplier’s recommended level, usually around 0.5-1.0%. Testing pH directly on the solid or paste is unreliable, so always test a diluted sample as described above.

Troubleshooting common issues

  • Bar is too soft: Reduce decyl glucoside or glycerin, and increase cetearyl alcohol or SCI.
  • Bar is too hard or crumbly: Add a little more decyl glucoside or glycerin next time.
  • Lather is weak: Increase SLSa or add a small amount of cocamidopropyl betaine, but keep the extra liquid low.
  • Bar cracks after molding: Pack the mold more firmly and avoid cooling too quickly.
  • Bar melts too fast in the shower: Store it on a draining soap dish and keep decyl glucoside below about 15% of the formula.

With the right balance of powdered surfactants, hardeners, and liquid decyl glucoside, you can create a mild, creamy shampoo bar that holds its shape and performs well on a variety of hair types.