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L’Oréal’s quest for 100% plant-based hair dyes

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Karl Wunsch

For over a decade, L’Oréal’s researchers have been on a ceaseless quest to develop a hair dye that is 100% plant-based, effective, ethical and suitable for home use as well as by professional stylists. Product Development Engineer Karl Wunsch tells us the story of an adventure in science that was full of challenges.

Taking on the challenge of developing 100% plant-based hair dyes

“I told myself many times, ‘We’ll never do it’”, recalls Karl Wunsch, Product Development Engineer at L’Oréal. Karl, who holds a PhD, was closely involved in creating the L’Oréal Group’s first wholly plant-based hair colour line. “Given that the Group’s DNA is mainly chemistry-centred, this was a totally new departure”, he explains.

The challenge was to come up with a new dyeing method that would use exclusively plant-based products and that would work without altering the hair in any way. Unlike synthetic dyes, which employ a series of chemical reactions to lighten the hair and attach the desired colour, the new product is activated using water only. The results include L’Oréal Professionnel’s Botanéa range, which is reserved for salons and designed for clients with up to 100% grey hair, and Color Herbalia by Garnier, which targets a more youthful group, including women who are up to 30% grey, and which makes the benefits of plant-based colour available to everyone.

“This is a revolution in colour design. Instead of trying at all costs to lighten and cover the hair in order to deposit the colour, we have shifted to a shading approach where the dyes attach to the hair and combine with its natural colour.” This keeps the hair’s relief and natural variations, making it possible to obtain highlights without having to start from scratch.

In terms of product benefits, initial consumer responses show that women love the shine, gorgeous colours and highlight-driven natural shading. They also appreciate the fact that the product lasts about as long as a permanent dye. Further benefits include a short application time (30 minutes to an hour) and compatibility with “technical services” such as bleaching, perming and straightening.

Plant-based powders offer an endless range of colours

After a decade of research into different plant extracts, L’Oréal’s researchers narrowed the search down to just three: henna, which yields copper tones, indigo for blues, and cassia, which is used to adjust highlight intensity. “We used these extracts to create three dye powders, which we blend in varying doses to obtain the desired colour.”

These combinations open up an endless world of chromatic possibilities. “We worked on an algorithm that identifies the optimal blends so that hairstylists can prepare the right solution for each client.” Stylists can use a digital app that analyses the client’s colour profile, lists possible shades with associated doses, and highlights the most popular combinations. “Since this is a highly disruptive approach to colouring, we wanted to provide stylists with maximum guidance. They can create their own blends or use existing combinations”, says Karl, who sees in this process a way for skilled stylists to regain their colouring expertise.

To activate the dye, the hairstylist just adds the powder to hot water to obtain a mix. It’s all about dosing and accuracy. “100g of powder to 300ml of hot water. The water hydrates each dye-containing leaf fragment. This makes it possible to extract the dyes from the plant matrix and channel them to the hair fibre, which swells naturally in the presence of water. Basically, water is key to colour in this process! After application, we leave the product to sit, holding the moisture in using a shower cap, then rinse”, says Karl, who adds that this step limits water wastage while making rinsing easier.

These new wholly plant-based dyeing products will also be available on the mass market with one key difference – consumers won’t have to make their own mixes. “We have prepared the blonde, copper and brunette versions in several ready-to-use levels of intensity.”

A challenge that gave sleepless nights to L’Oréal’s research teams

Water and powder – simple enough on paper. But the technical challenges behind the apparent simplicity were a major headache for L’Oréal’s research teams. “We wanted to stay 100% plant-based without compromising on colour while keeping the application time to one hour or less. The formulation was a challenge, as was determining the routine based on the selected shade.”

“We applied the scientific rigour that we learned in chemistry to plant research”, Karl goes on to explain. “So even when working with plant-based materials, which are inherently less predictable than chemical transformation processes, we wanted to control and understand everything.” To do this, the researchers used an algorithm to identify the best blends.

To verify the mathematical model underpinning the algorithm, the team criss-crossed Europe, travelling to Denmark, the UK, Italy, Spain and Germany. “We observed how the plant-based dyes affected different types of hair. With very light blondes, we got a sunny, naturally golden effect that Scandinavians love. For brunettes, we set up a two-stage routine to get rid of the green highlights that can be caused by indigo, even if they vanish naturally in a few hours.”

Getting the practical properties right was a challenge as well. Several oils were identified as candidates to coat the powder. Coconut oil was chosen because it can aggregate the finest leaf fragments during coating to make the power less volatile. When hot water is added, the coconut oil melts to give a creamy consistency that facilitates mixing, application and rinsing once the application time is done.

Another key issue was to devise the application method for this new approach. The temperature of the hot water that the powder has to be mixed with varies depending on the shade. How were customers and stylists going to obtain water at the right temperature? By mixing boiling and cold water. But the temperature of tap water depends on location and the time of year. “We consulted with our research units in Japan and Brazil to check application using their tap water and test the protocol’s operational thermal range. That’s just one example from the hundreds of checks that we performed.” The formulation and the application routine evolved together to obtain the best-looking results.

Once the combinations and application method were settled, it was time for large-scale quantitative testing. In all, 1,000 applications by over 100 hairdressers were used to carry out the final assessments, with celebrity stylists taking part in the very last round of tests. “When I saw that some of the leading stylists in the field were onboard, I knew that we really had something.”

“These new product lines distil ancient knowledge and state-of-the-art plant-based dyeing technology, combined with our scientific rigour”, says Karl in conclusion. It’s a winning combination, naturally.