Hair shine and colour vibrancy: a unique methodology to validate hair care formulations

The term “shine” represents the ability for light to reflect off a surface and therefore depends on two important parameters: the surface and the light. Hair shine relates to the interaction of light with the hair surface; the more light that is reflected from the hair surface results in a hair tress that appears shinier. There are many factors that can influence shine, as this attribute is closely linked to the hairs surface properties. Let’s explore some examples:

Cuticle condition
The fundamental factor that influences hair shine is the condition of the hair cuticle. Cuticles that are less damaged appear flat and smooth and are able to reflect light more easily, resulting in a shinier hair surface. A damaged hair surface can feel rough and present split ends due to raised cuticles. This means that the hair surface is not able to reflect light as easily, and therefore makes the hair appear dull.

Natural hair morphology
Hair fibre alignment is another important factor when it comes to hair shine. Dense, well-aligned hair fibres are able to reflect light more easily and therefore generate more shine. This is why straighter hair types generally appear more naturally shiny. Curly and coily hair types have areas of discontinuity in the cuticle layers due to the kinks and twists that naturally occur along the hair fibre, which makes it harder for light to be reflected. Even with a smooth hair surface, curly hair is inherently less shiny due to the natural shape of the hair and the inability to align in the same way as straighter hair types. As shine is often synonymous with healthy hair, this has often led to the use of relaxer systems for curlier hair types, in an effort to achieve straighter, more aligned tresses. But this treatment is particularly damaging and with repeated use can ultimately damage the hair surface and reduce hair shine once again.

Hair colour
Whether it be natural or artificial, hair colour influences the way in which light can be reflected by the hair and therefore influences shine. Darker hair colours are inherently shinier as they reflect more light than they absorb, whereas lighter hair colours absorb light which causes less light reflection and therefore less shine.

With many consumers often choosing to dye their hair, whether it be for natural hair colour maintenance or as an outlet for self-expression, the desire for long-lasting, vibrant hair colour transcends all consumers. Hair vibrancy is defined as a vivid, bright and striking colour, and is key to the perception of a good hair colour. Colour vibrancy takes shine and colour into account, so when hair colour begins to fade or hair appears less shiny, this can prompt consumers to dye their hair again in an attempt to inject life back into their dull tresses. But as we know, this is a damaging styling practice. Inflicting more damage on the hair is not the answer when we want shinier hair; as we learnt earlier, damage to the hair cuticle can negatively impact hair shine. So, what is the answer? Let’s first understand how to quantify hair colour vibrancy.

Colour vibrancy is notoriously difficult to measure on the hair, so Croda has developed a unique methodology to quantify the vibrancy of hair, known as the Hair Colour Vibrance Factor (HCVF). By utilising the SAMBA system from Bossa Nova Vision, the HCVF considers two defining parameters for vibrancy: lustre and chroma.

Lustre relates to the shine and is defined as the first, initial reflection of light from the hairs surface.

Chroma relates to the colour, which is identified from the second reflection of light that is reflected after light penetrates the hair fibre.

The Hair Colour Vibrance Factor is defined as: