Hair colour shampoo works by depositing or absorbing pigment into the hair shaft, altering its colour in a convenient and less time-consuming way compared to traditional hair dyes.
Here's a breakdown of how it functions:
Pigment Delivery
The core function revolves around delivering pigment to the hair. Unlike traditional hair dyes that permanently alter the hair structure with ammonia and peroxide, hair colour shampoos use a milder approach.
- Deposit-Only: Most hair colour shampoos work by simply depositing colour onto the hair's surface. The pigments cling to the outer layer of the hair shaft, providing a temporary colour change. This is why the colour washes out gradually with each shampoo.
- Absorption (Lesser Extent): Some formulations might contain ingredients that allow for a slight absorption of the pigment into the hair's cuticle (outer layer), leading to a slightly longer-lasting effect than purely deposit-only shampoos.
Shampoo Formulation Enhancements
The shampoo base facilitates the pigment delivery process.
- Cleansing Agents: The shampoo cleans the hair, removing dirt and oil, which helps the pigment adhere more effectively.
- Conditioning Agents: Many hair colour shampoos contain conditioning agents to help smooth the hair cuticle, allowing for more even colour distribution and added shine. This helps counteract potential drying effects from the cleansing agents.
- pH Levels: The pH of the shampoo can play a role in how well the pigment adheres to the hair. Some formulations might be slightly acidic to help open the hair cuticle, allowing for better pigment penetration (though still significantly less than permanent dyes).
Comparison to Traditional Hair Dye
Here's a table comparing hair colour shampoo to traditional hair dye:
| Feature | Hair Colour Shampoo | Traditional Hair Dye |
|---|---|---|
| Colour Change | Temporary, washes out gradually | Permanent (until hair grows out) |
| Chemical Process | Deposit-only or slight cuticle absorption | Opens cuticle, penetrates cortex, alters hair structure |
| Ingredients | Pigments, cleansing agents, conditioners | Ammonia, peroxide, pigments |
| Application | Shampooing | Multi-step process, longer application time |
| Hair Damage | Minimal | More likely to cause damage |
Key Considerations
- Colour Selection: Hair colour shampoos work best for enhancing existing hair colour or adding subtle tones. They are not as effective for drastically changing hair colour, especially going from dark to light.
- Hair Porosity: Porous hair (damaged hair with raised cuticles) tends to absorb pigment more readily, potentially resulting in more intense colour and faster fading.
- Washing Frequency: Frequent washing will cause the colour to fade faster.
Conclusion
Hair colour shampoo offers a convenient and gentle way to temporarily enhance or subtly change hair colour by depositing pigment onto the hair shaft during the shampooing process. Its ease of use and minimal damage make it a popular alternative to permanent hair dyes for those seeking a temporary colour boost.
