'There was an ambience in the lighting that was very special,' says Mercier of the period

Mercier enrolled in the prestigious but now defunct Carita School where she trained as a make-up artist

As somebody who has forged a cosmetic empire on the foundations of 'the natural look', it is pleasantly reassuring that in person Laura Mercier is largely without artifice.

We meet in the Reading Room of Claridge's, her "home away from home" when in London, although pinning down her actual home proves difficult for the make-up artist who largely splits her time between Paris, Provence and America. Her face is immaculately made up to look as if she is almost wearing no make-up, her skin glows and eyes flash as she animatedly talks of her experiences from more than three decades in the business.

After graduating from art school in Paris in her late teens, Mercier enrolled in the prestigious but now defunct Carita School where she trained as a make-up artist. Having qualified as an aesthetician, Mercier began assisting Thibault Vabre, "a famous and talented" artist who went on to become creative director of brands such as Lancôme and Clarins. "I was interested in anything graphic," says Mercier of studying painting. "Not the architecture part of it, just the graphics. It was like training for precision and knowledge of textures and colours. I would advise it to anyone who wants to do make-up. It's crucial to me to know how colours complete each other or cancel each other, and if you don't have these basics, it's lacking. I didn't know what I wanted to do though, besides being a starving artist."

"From [Carita] the door opened to becoming a make-up artist. I became friends with [Vabre] and he took me on as an assistant. That's how everything began." Mercier then became an artist in her own right, working for magazines as a freelancer for six years, as well as teaching make-up artistry.

In the early Eighties she moved to New York as part of the team responsible for launching American Elle. "At the time you had a network of fashion teams in New York, and a network of fashion teams in Paris, and they were basically doing collections and shows – it wasn't international like now. So when I decided to go there, people in the advertising business and the fashion magazines did not know me especially, I had to start over, with an agent and a career.

"I was pretty established in six years in Paris, I had to start over like a debutant in New York. In my head I separate my two careers – my first in Paris and then it's like my life started over again. It was a good learning experience about America – the way they work, the looks, and perfecting a different exploration of make-up."

Those who remember the Eighties – or have seen its cosmetic legacy – will know that the overriding aesthetic was not one in tune with Mercier's naturalistic style. Blue eyeshadow, stripes of pink blusher and a heavy powder are the antithesis of Mercier's signature flawless face.

I was very French, very European in my style, in the sense that make-up was much lighter and more natural. But there was a change in the industry, Elle magazine was really about being fresh and natural, as well as being sophisticated," she explains. "America had been stuck in the same type of make-up, that heavy make-up, skin in particular. Elle brought a fresh approach because of the cosmopolitan aspect of mixing models – before you had dark skin magazines or Caucasian magazines, so that was very new."

Although the American industry was changing – in part because of Mercier's influence – she still found the culture, and the aesthetic, a struggle at first. "I had to force myself to build thick foundation and give them the look they were expecting. I never had a heavy hand though, no matter what. I liked to see fresh young skin through [the foundation] that 'glowy' make-up didn't exist."

As Mercier built a reputation as a proponent of the natural look, she found herself becoming more in demand, especially as the Nineties dawned and the trend for minimalism went large. Still she struggled with the cut-throat nature of the business. "The opportunity was giant in America compared to France – and it's a jungle so it pushes you to your limits. It was torture, it goes against who I am entirely. Everybody was stepping on your toes, stealing your jobs, going behind your back. Every time someone would push me aside I'd say 'OK, be my guest'. But because you're a freelancer, you have no security and you have to be the best you can be every day, a good character, a fun person to be with. You have to have humour even when you want to punch [your colleague's] face. You've got to stay focused, strong and grounded. And it's not easy."

Although Mercier has experienced working with some characters "from the ones who are on drugs to the ones who are dictators, and the ones who have a big head because they are in power", she realises that working can build confidence as well as power, but it is important to remain humble – and have an exit strategy, and a plan B.

As one of the top make-up artists in the world, Mercier has worked with renowned photographers such as Irving Penn and Steven Meisel, who she credits with pushing her to explore her talent. Although at the top of her game, and commanding huge fees, as a freelancer Mercier was aware that she could fall out of favour and lose everything. Starting a cosmetics line was a way of achieving a sense of security. "I gave everything to my career, I was really settled and felt very safe but at one point I was tired of it. I thought I wasn't passionate any more. I wanted to do something else and I was passionate about product and textures, and the making of it, putting my fingers in the pots and making colours. I remember saying to myself, 'one day, if I do my own line, the first product I will ever do is camouflage [a heavy concealer that is used to hide all flaws], because I do not understand why it doesn't exist.

"The brands, the big empires, never really followed what was going on. It took them years to finally have some foundation with a yellow base for olive tones and it took a make-up artist brand to show them the way."

With her experience of working with so many different skin tones, Mercier knew that this was the area on which she wanted to first focus. "I knew I didn't want to build my own business. I had no money to build it with and no business talent – I was the crazy artist, so I needed someone solid."

After two unsuccessful attempts at starting a line, it was third time lucky for Mercier and a Texan woman who provided the requisite financing and business experience.

"She interviewed five of us and she chose me because I had a concept ready. She asked if I had an idea for three products that were different from what already exists. I said, 'Three? You must be kidding, I have 10!"

Mercier was called on to make in-store appearances, something she relished. "I'm always inspired by real people; I'm part of the real people! That's where you learn the most. It's a beautiful thing to think that you can share your talent and your expertise with the world and help women get something that they need to feel more confident. I don't want to intellectualise what I'm doing, but it certainly has meaning."

These appearances led her to develop a more holistic approach for the staff at her make-up counters. "We trained people to pay attention, spend as much time as was needed on the floor, make-up classes were free. We established the make-up artistry to a semi-professional level.

"It's not just about the new colour that you shove in their face and say 'this is a beautiful yellow and blue, deal with it', after all every time we touch the face something amazing happens."