How Silicone Got Into Your Shampoo, and Why Its Name Is a Mistake

How Silicone Got Into Your Shampoo, and Why Its Name Is a Mistake
Flint, quartz and sand: where silicone's story starts.

Silicone started as a chemist's wrong guess about some sticky goo made from quartz. It ended up in nearly every bottle of shampoo. Here's what it actually does, told fairly.

In 1873 a chemist named James Emerson Reynolds gave a lecture with a title that sounds like a riddle: "On Alcohols from Flint and Quartz."

He was chasing an old hunch. Silicon sits just below carbon in the periodic table, and carbon is the backbone of every living thing. Chemists wondered whether silicon could do the same tricks, and whether there might be a whole second chemistry built from sand and stone.

At the University of Nottingham, Frederic Stanley Kipping spent decades trying to find out. In his flasks he kept producing thick, oily, stubborn substances that wouldn't crystallize. In 1901 he wrote their formula as R₂SiO. On paper it looked just like a ketone, the carbon family that includes acetone, which is written R₂CO. So he called them "silicoketones," and the name shortened to silicone.


Frederic Stanley Kipping (1863–1949), the chemist whose “silicoketones” gave silicone its name.

The name was a misnomer, and Kipping knew it. These weren't small ketone-like molecules. They were long chains, silicon and oxygen alternating link after link, with little carbon groups hanging off the sides. Chemists now prefer the word siloxane. Late in his career, Kipping doubted that silicon would ever amount to much.

He was wrong about that too.

From quartz to bottle

The route still begins with stone. Quartz sand or quartzite is heated with carbon until the oxygen is stripped off, which leaves silicon metal. The metal reacts with methyl chloride to make chlorosilanes, and adding water to those links them into silicone chains. In 1943 Dow Chemical and Corning Glass formed a joint company, Dow Corning, to make them at scale.

Silicones went into gaskets, sealants, lubricants and medical tubing. And then, in 1987, they went into shampoo in a way that changed the bottle.

The 1987 trick

Two-in-one shampoos already existed. Early versions from the 1970s used positively charged polymers. In the bottle, those polymers bundle together with the shampoo's cleansing molecules into tiny droplets called a coacervate. When rinse water dilutes the lather, the droplets break apart, and the positively charged polymer is drawn to hair, which carries a slight negative charge. Formulators call this "dilution deposition."

Procter & Gamble's Pert Plus, launched in 1987, was the first 2-in-1 to use silicone as its main conditioning agent. As the shampoo is rinsed, the coacervate clumps, traps fine silicone droplets and lays them down along the hair fibre. The cleanser leaves with the water and the silicone stays. One industry account says that today most shampoos deliver cleansing and conditioning in one formula.

It was a genuinely clever bit of chemistry, and it's worth saying plainly what it does well.

The fine-hair problem

Picture a single fine strand. It's thinner than average, so it has less to carry any weight with. Wash after wash, a smooth film gets laid down, and some of it stays. The strand feels silky in the hand. By afternoon, though, it lies flat against the scalp, because the film that makes thick hair glossy can make fine hair heavy.


Illustration: a heavy film can weigh a fine strand down (top); a lighter coating leaves it free (bottom).

Hairdressers describe this as hair being weighed down. It's not damage. It's simply the result of a film designed for a different head of hair.

Where Flint & Stone sits

Flint & Stone takes a different route to slip and strength. It's two bars, a shampoo bar with 8 ingredients and a conditioner bar with 14, and the conditioning comes from rice protein, which coats each strand so hair feels stronger, breaks less when it's brushed, and looks fuller.

Hair that's used to a silicone film can feel different for the first few washes while the old layer rinses away.

There's a quiet irony in it, too. The molecule began as "alcohols from flint and quartz." A bar called Flint & Stone just reaches for the rice instead

Sources

Image credits

  • Top image: Flint & Stone.
  • Second image: Photographer unknown, portrait of Frederic Stanley Kipping (via Prabook). License: Public domain (PD-UK-unknown; PD-US). Source: Wikimedia Commons.
  • Third image: Flint & Stone.
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