Someone, somewhere, at this moment, is painting her nails – or having them painted – in an act of self-expression designed to telegraph her mood, her character, her desire, maybe even her politics.

Hands – nails in particular – are not just the "key accessory" of spring, as beauty editors at several magazines have pronounced. Nails have become the small, painted canvas of the mind and a silent, powerful voice of unapologetic femininity.

In his book Nailed, Carlos "Dzine" Rolon looks at nail adornment in previous cultures. In ancient Egypt, for instance, nail colour was a sign of social status and sex appeal, while members of the upper class during China's Ming Dynasty kept long nails, flecked with gold, to underscore their freedom from manual labour. "Nail art has been around for a long time," the author explains on the phone from Dallas. "Egyptians had gold caps on their fingers long before Beyoncé wore hers."

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A multimedia artist, Rolon created an art show, Imperial Nail Salon, a kind of pop-up nail parlour, in tandem with the book. In 2011, it was a hit in New York and at Art Basel in Miami, where Tilda Swinton sat for an ornate nail-art session and later wore one of the artist's baroque hand ornaments. The installation will pop up again, in Chicago, later this year.

To appreciate the modern age of adornment, just look online to see where nail art and culture are headed.

In February, the Nail Olympics, founded in 2001, were held in Rome, attracting nail artists from around the world for a two-day competition that makes Edward Scissorhands look tame. Last month also saw the New York debut of NAILgasm , a documentary by Ayla "Brass" Montgomery, which explores how nail art – once a subcultural ghetto aesthetic celebrated by eighties hip-hop artists – has become a mainstream phenomenon in the past two years. And in 2011, the first Nailphilia Exhibition, celebrating the "collision" of the nail world and art world, took place in London.

Quite apart from these outré expressions of nail art, nail-polish colours and patterning techniques have also become obsessions in the wider culture.

A record total of $7.47-billion was spent in nail salons in the United States last year, according to Nails Magazine, while drugstore sales of polish and nail products are up by 59 per cent. Nails now serve as mini-placards or, as I like to think of them, shiny, colourful fenders on the car of self.

When U.S. first lady Michelle Obama wore blue-grey nail polish during her speech at the Democratic National Convention last year, her choice set off a chatter-storm on the Internet, even prompting some political commentators to mention her partisan colour. Her Twitter feed, @FLOTUS, sent 42,352 new visitors to the website of Artistic Nail Design, the company responsible for her nails. Patriotism was also expressed on the fingertips during the 2012 Summer Olympics, where several athletes sported specialized national manicures. In the late 1980s, Florence Griffith-Joyner, the late American track-and-field athlete, sported long, star-spangled nails, but the tastefulness of her style was questioned. Today, nail art is no longer considered somewhat tacky. Now, it's simply cool.

There have even been instances of nail activism. New York-based nail fanatic Casey Danton painted "No H8" on her nails last year as an anti-bullying statement, earning her thousands of followers on Instagram. She currently writes a blog, Dull Like Glitter: Saving the World One Nail at a Time.

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Social media and the recession have been key elements in the growth of nail polish, Ann Mack, director of trendspotting for the marketing firm J. Walter Thompson, says in a phone interview from New York. Nail polish is the new lipstick, the small, affordable luxury that is a "mood-lift accessory." But the growth in the marketplace, Mack notes, also comes from innovation, as manufacturers such as Essie meet demand with stickers and patterning techniques that are available in drugstores.

The desire to wear nail polish is so strong that Inglot Cosmetics, an international beauty brand, has devised a breathable nail polish that satisfies the requirements of devout Muslim women who are unable to wear regular polish because of the washing ritual involved in daily prayers.

Nail primping is a function of a sisterly female culture in which the client and her technician sit across a table from one another, holding hands by necessity, forcing an intimacy that is hard not to indulge with some kind of friendly verbal exchange about family, children, husbands and social activities.

As Jezebel, the notoriously feminist website, has noted approvingly, "nail art ... might be the only form of primping and grooming that isn't rooted in making oneself more appealing to men or exploiting women's insecurities. It transcends skin colour and hair texture and face symmetry and body type." And it defiantly confronts dated standards of demure femininity. In NAILgasm, Jennifer Yu, the communications director of LVMH's fashion division, says that nail art "empowers us women to have our own voice." It's about not caring what others think, she adds.

And not only that. As a friend of mine once observed, the veneer on the nails is a bright, hard, un-chippable shell that makes others think you're firmly put together, even if you're feeling wobbly emotionally. Polished nails, in other words, are psychological aids, always within view. Deborah Lippmann, a celebrity manicurist who has a line of luxury nail and hand products, told me recently that some of her fans tweet about how they choose colours based on how they want to feel. "I read someone tweeting that she was getting her nails prepped for the coming week with No More Drama [the colour Lippmann designed with Mary J. Blige] because 'that's the kind of week I want.' "

The evolution – or society's re-acceptance – of nail adornment is exciting and overdue, Lippmann feels. "There was a long period of time when wearing red nail polish to the office was considered really inappropriate. It was too sexy. It drew too much attention. And it was thought that women shouldn't be noticed in that way. There were so many rules. And those are gone now.Not in all workplaces, but, in many, women feel free to wear what they want on their nails."