Swish set: Swetha Sivakumar brushes up on nail polish

There is so much chemistry at work here, between the polymers, solvents, pigments and photochemistry, that each glass bottle might as well be a tiny laboratory.

My teenage daughter loves nail polish. She can spend hours scrolling through Pinterest, studying intricate designs, and painting and repainting her nails. Every shopping trip turns into a negotiation, with her pleading to buy yet another shade she claims to have been searching for “forever”.

(Adobe Stock)

Her fascination with nail polish both amuses and confuses me. I’ve always kept my nails short and clean, my indifference to cosmetics shaped partly by personality and partly by a conservative upbringing.

A few months ago, I decided to explore her newfound passion and see if I could share in it. I have since become fascinated by these shiny, varied, quick-setting varnishes.

There is so much chemistry at work in these cosmetics, with their polymers, solvents, pigments and photochemistry, that each glass bottle might as well be a tiny laboratory.

The more I’ve learnt, the more intrigued I have become, and I’ve been peppering my daughter with questions. She is now the amused one, patiently explaining drying times, pigment finishes and builder gels. So, what have I uncovered, about this world that sits at the intersection of cosmetics, chemistry, biology and art?

Let’s start at the beginning: Why do humans have nails?

Their primary function is mechanical. Nails provide counter-pressure to the soft tissue of the fingertips, improving fine motor control. This rigidity allows us to grip small objects, manipulate tools and perform precise tasks. They offer a massive evolutionary advantage over claws.

Meanwhile, the keratin cells are tightly packed, creating a hard, compact surface that protects the fingers from falling objects, and from scrapes while gripping (or, in another era, digging or even walking). With their smooth, slightly translucent surfaces, it isn’t surprising that humans have, for thousands of years, treated the nail like a tiny canvas.

In ancient civilisations, painting them simply involved staining them with natural dyes such as henna (which is made, incidentally, from the powdered leaves of lawsone plants). In ancient China, mixtures featuring egg whites, beeswax and vegetable dye were used.

Early modern nail polish borrowed heavily from automotive paint technology. Today’s nail polish is far more complex, because it has to do a lot more. It must last long and not fade, brush on easily and evenly, dry quickly and adhere well to the nail but also last long in the bottle.

This requires some careful chemical engineering.

At its core, the varnish is made up of solvents that will allow the polish to evaporate quickly (for that quick-drying effect); nitrocellulose, a polymer derived from cotton (for the glossy finish); and, because nitrocellulose is brittle and does not adhere well on its own, polymers and plasticisers to keep the overall effect intact for longer.

Finally, there are the pigments: tiny, solid particles that give the polish its colour.

This is where things become really interesting. The colours themselves may be organic (such as the pinks and reds made from carbon-based molecules) or inorganic (the blues, purples, whites and numerous other shades made from metal compounds, because safe-to-use natural sources are rare).

The eventual look of the painted nail is often determined by a metallic element too. Pearlescent surfaces need flat particles derived from mica or metal oxides to reflect and refract light. Magnetic particles such as black iron oxide can help the polish move and align in ways that form a swirl or pattern. Glitter requires larger reflective particles, often made from tiny shards of metal or plastic polymers.

Mix these elements together in proportions that guarantee longevity and one has the tiny finished lab in a bottle.

Gel nail polish, incidentally, relies on an entirely different chemistry. Instead of simply drying on the nail, its small reactive molecules (called acrylate monomers), when exposed to UV light, link together and snap into place to form a smooth, solid polymer bonded to the surface beneath. This gives such polish its signature gloss and durability, but also makes it difficult to remove. If the gel polish isn’t cured properly, it can leave unreacted acrylates behind to interact with the skin as well. These can cause allergic reactions, not just to such nail paint but to anything that contains such acrylates, and that list can include dental fillings, certain medical bandages and craft supplies. My daughter and I are not always in agreement, but we have agreed to avoid these risks.

As for the rest, along with millions around the world, her nails continue to serve as her smallest canvases of self-expression. And these days, with each new pattern she tries out, I’m tuning in to take a closer look too.

(To reach Swetha Sivakumar with feedback, email upgrademyfood@gmail.com. The views expressed are personal)