Why do hair masks use two different hydrolyzed proteins?
Short answer
They do different jobs. Hydrolyzed keratin has an affinity for damaged sites and fills the gaps for strength; hydrolyzed wheat protein is smaller and more hygroscopic, so it attracts and holds moisture in the shaft. Used together they work synergistically.
Explanation
The book's intensive repair mask carries hydrolyzed keratin at 3%, hydrolyzed wheat protein at 2% and panthenol at 2%, all added in the cool-down phase at about 45 °C.
Keratin is chemically close to hair's own protein, so it has an affinity for the damaged sites along a weathered or chemically treated shaft and fills those gaps, restoring strength. Wheat protein is a smaller molecule and more hygroscopic; rather than patching structure, it attracts and retains moisture inside the hair. Panthenol, provitamin B5, penetrates the shaft and improves elasticity.
The proteins go in after the emulsion has formed and cooled, because heat and high shear both degrade them. The mask is then taken to pH 4.0–4.5 so the cationic conditioner, BTMS-50, can deposit properly and seal the cuticle over the protein layer.
What to do
- Add proteins below about 45 °C, with gentle stirring rather than high shear.
- Pair a structural protein with a humectant protein instead of doubling one.
- Follow a protein treatment with enough conditioning lipids, or hair can feel stiff.
Source: The Big Book of Homemade Hair Care — The Intensive Repair Hair Mask