What is purple shampoo, how does it work on a scientific level (i.e., what’s the mechanism behind the color correction), and who would benefit the most from using it? Specifically, I’m interested in understanding the nuances of applying it to different shades and types of blonde, silver, gray, and even light brown hair. Are there risks associated with overuse, and if so, what are they and how can they be mitigated? Are there alternative products that achieve similar results, and how do they compare to purple shampoo in terms of effectiveness, cost, and potential side effects? Finally, can you recommend specific purple shampoo brands or formulations for different hair types (e.g., dry, oily, fine, thick)?

Answer

Purple shampoo is a shampoo containing violet pigment designed to neutralize brassy or yellow tones in blonde, lightened, or grey hair. It works on the principle of color theory, where purple and yellow are complementary colors and sit opposite each other on the color wheel.

Here’s a detailed breakdown of how it works:

The Problem: Brassiness and Yellow Tones

• Underlying Pigments: All hair contains underlying pigments. In dark hair, these are typically red or orange. In lighter hair, they are yellow.
• Lightening Process: When hair is bleached or lightened, these underlying pigments are revealed. The lightening process aims to remove these pigments, but often it cannot remove them completely, or they can reappear over time.
• Environmental Factors: Various external factors contribute to brassiness. These include:
  • Sun exposure: UV rays can oxidize hair and reveal warm tones.
  • Hard water: Minerals in hard water, such as iron and copper, can deposit on the hair shaft and create a yellow or orange hue.
  • Chlorine: Chlorine in swimming pools can react with hair proteins and lead to discoloration.
  • Product buildup: Residue from styling products can accumulate and create a dull, yellowish cast.
  • Natural oils: Natural oils can also contribute to brassiness as they oxidize.

The Solution: Color Theory and Purple Pigment

• Complementary Colors: As mentioned, purple and yellow are complementary colors. Complementary colors neutralize each other when combined.
• Purple Pigment Deposition: Purple shampoo deposits a small amount of violet pigment onto the hair shaft. This pigment counteracts the yellow tones, making the hair appear cooler, brighter, and less brassy.
• Temporary Effect: The effect of purple shampoo is temporary. The purple pigment is deposited on the surface of the hair and washes out with subsequent shampoos. This is why purple shampoo needs to be used regularly to maintain the desired tone.
• Intensity Variations: Purple shampoos come in varying intensities of purple pigment. Some are more heavily pigmented than others. The intensity of the shampoo determines how much neutralization occurs with each use.
• Understanding Undertones: Different levels of lift(lightening) will have different undertones. Higher levels of lift will have pale yellow and require lighter shampoos with gentle toning. Lower levels of lift will have Gold or orange undertones and require more pigmented purple shampoos.

How to Use Purple Shampoo Effectively

• Frequency: Usage depends on the hair’s brassiness and the shampoo’s intensity. Generally, use 1-3 times per week, alternating with a regular shampoo. Overuse can lead to a purple or lavender tint, especially on very light or porous hair.
• Application: Apply to wet hair, focusing on the areas with the most brassiness.
• Processing Time: Leave the shampoo on for the recommended time (usually 1-5 minutes, but follow product instructions). Longer processing times result in more neutralization but also increase the risk of purple staining.
• Rinse Thoroughly: Rinse thoroughly with cool water.
• Conditioner: Follow with a moisturizing conditioner, as purple shampoo can sometimes be drying.
• Patch Test: Perform a patch test before applying all over to see how your hair reacts.

Considerations and Precautions

• Hair Porosity: Porous hair (damaged, chemically treated, or naturally very porous) absorbs pigment more quickly and is more prone to purple staining. Reduce processing time or dilute the shampoo.
• Hair Color Level: Purple shampoo works best on blonde, lightened, or grey hair. It is not effective on dark hair, as the purple pigment will not be visible.
• Purple Staining: Overuse or excessive processing time can cause a temporary purple tint. If this happens, use a clarifying shampoo to help remove the excess pigment.
• Dryness: Purple shampoo can be drying due to its cleansing properties. Use a moisturizing conditioner and hair mask regularly to combat dryness.
• Alternatives: Purple conditioners, masks, and toning treatments are also available for a gentler approach to neutralizing brassiness.
• Ingredients: Some purple shampoos contain sulfates, which can be harsh on the hair. Consider sulfate-free options, especially if you have dry or sensitive hair.
• Not a Replacement for Toner: Purple shampoo is a maintenance product, not a replacement for professional toning services. Toning at a salon provides a more precise and long-lasting color correction.
• Grey Hair: Purple shampoo can help brighten grey hair and prevent it from yellowing due to environmental factors. However, it is important to choose a formula specifically designed for grey hair, as some purple shampoos can make grey hair appear dull.
• Vegan/Cruelty-Free Options: Many vegan and cruelty-free purple shampoos are available on the market.
• Allergy considerations: Some formulas will include added fragrances and if you have allergies, read the ingredient list to be aware of this.