What Causes Hair Brassiness? | The Science Explained | Fergal Doyle Hair Bristol

Brassiness is one of the most googled hair problems in the UK — and with good reason. Almost every client who lightens their hair will encounter it at some point. Understanding exactly what causes brassiness is the first step to preventing and managing it. Here's the science behind brassy hair, explained simply by the colour experts at Fergal Doyle Hair in Bristol.

The Role of Underlying Pigment

Every strand of natural hair contains melanin — the pigment that gives hair its colour. There are two types: eumelanin (dark brown and black) and phaeomelanin (red and yellow). When a colourist lightens hair, they use hydrogen peroxide to break down the melanin. But the warm phaeomelanin pigments — red, orange and yellow — are the last to be dissolved, which is why lightened hair passes through orange and yellow stages on the way to platinum.

Why Toner Fades and Brassiness Returns

After lightening, your colourist applies a toner to neutralise the warm pigments and achieve your desired shade. Toner is a semi-permanent colour — it gradually washes out over 4 to 8 weeks, depending on how porous the hair is, what shampoo you use and how frequently you wash. As the toner fades, the underlying warm tones become increasingly visible again. This is completely normal and expected.

Factors That Make Brassiness Worse

Several factors accelerate toner fade and the return of brassiness: washing hair with hot water (opens the cuticle and strips colour), using sulphate-heavy shampoos (strip pigment faster), sun exposure (UV breaks down colour molecules), hard water (mineral deposits alter tone), heat styling without protection (degrades colour), and swimming in chlorinated water (chemically alters pigments).

Can You Prevent Brassiness Completely?

You can't prevent it entirely — it's a natural consequence of lightening — but you can significantly slow it down. Using sulphate-free, colour-safe shampoo, washing in cool water, using purple or blue toning shampoo weekly, applying UV protection products and booking regular toning gloss appointments at the salon will all make a substantial difference to how long your colour stays cool and vibrant.

Book a Toning Appointment at Fergal Doyle Hair Bristol

If your hair has gone brassy, a professional toning gloss at Fergal Doyle Hair will restore it in as little as 30 minutes. Visit us at Clifton (154 Whiteladies Road BS8 2XZ) or Stoke Bishop (19 Druid Hill BS9 1EW). Book online at fergaldoylehair.com or call 0117 244 3165.