Why, why do we battle brassiness? What actually is going on?
To understand brassiness, we must understand Natural Contributing Pigment (NCP).
Natural contributing pigment is the varying degree of warmth exposed during the lightening process.
Natural pigment is the pigment which remains in the hair after lightening or applying colour and these pigments contribute to the final colour result.
When lightening hair colour, the natural hair colour goes through various lifting stages. The chemical process of hair colouring breaks down the natural pigment (melanin) in the hair, removing it from the cortex, replacing it with hair colour which is deposited in the cortex for a permanent colour result.
As hair lightens, melanin is removed in order of the size of the molecule, which ranges from darkest to lightest, and the underlying tones are exposed. Black is the largest and easiest to remove, and yellow is the smallest and most difficult—this means that the colour always gets warmer as pigment is removed.
The natural pigment left in the hair at the desired level is referred to as Natural Contributing Pigment (NCP) and is different at each colour level.
Understanding and accounting for NCP is critical not only in correct colour selection for routine colouring, but also for any colour correction or colour balancing processes.
NCP is not a factor unless you are lightening. Tonal results are always a combination of what pigment is in the hair naturally (NPC) and what tone of colour you use when colouring.
NCP can also be used when filling hair that has been over lightened. To return to the natural colour, a filler colour is used to replace pigment that was lightened out of the natural hair colour. This will allow you to create the level and tonal value desired.
Once you determine the NCP, then you can work with the Colour Wheel to determine the tonal series needed to achieve the desired colour results. As all NCP is warm, typically the best option to manage unwanted warmth is to select a colour on the opposite side of the Colour Wheel, such as a cool colour, which will counter-act and neutralise unwanted warmth.
The graphic above illustrates the tones revealed when lightening each colour level.