Meet Mr. Mauve

His name is William Henry Perkin. I bring him up because reader Antuanete wants to know what precisely coal tar dyes are and how they’re made. I confess that the specific chemistry of synthetic dyes is mostly beyond me. What I do know is that the world’s first synthetic dye was a kitchen accident. It happened in 1856 when Perkin, then an apprentice to the legendary German chemist A.W. Hoffman, attempted to create synthetic quinine (an expensive tree bark extract that was a critical malaria medicine) over his Easter vacation. He combined aniline, a by-product of the coke-making process, with potash and sulfuric acid. The goo he made was not even a little bit like quinine, but when Perkin combined it with alcohol, a sort of purple was the result.

Convinced he had something of value on his hands, Perkin showed is potion to Hoffman who immediately instructed him to throw the mess out and get back to work. It wasn’t a matter of simple short-sightedness on Hoffman’s part. The eminent chemist correctly saw that isolating whatever it was that produced the color from the Perkins’ hydrocarbon soup would be a very difficult job indeed. Hoffman vastly preferred to work with materials that crystallized, as crystals yield pure isolates (think of water freezing on a dirty pond…the water below stays dirty, but the ice above is clear and mostly pure).

But Perkins was too excited to stop. Being an amateur painter he had a clear understanding of what it would mean should he be able to produce a color as valuable as purple from a material as cheap as coal residue. For up until that time, all dyes, whether for food or textiles, were made from naturally-occurring substances. That sounds great to us now, though harvesting colorings from natural sources was hideously expensive and labor-intensive. Then, the only way you could get a heat, light and water resistant purple clothing dye was by milking the hypobranchial glands of Mediterranean sea snails. Try doing that for minimum wage Monday through Friday. No wonder purple clothes were worn solely by royalty dating back to the ancient Persians.

In time Perkins did succeed in purifying his dye. He dubbed his compound “mauveine” and promptly put it on the market, where it was put to use as a silk dye. The violet color became known as “mauve” and while the color itself never took off as a commercial product, the process Perkins invented was soon used to synthesize all sorts of other colors (roughly 700 by the turn of the nineteenth century). Most of them were used in the textile industry, though some were put to use in food. Perkins became a millionaire and a legend. The Mediterranean snail gland futures market, by contrast, tanked.

Here I should insert that while all colorings made via the manipulation of hydrocarbons are called “coal tar dyes”, none of them are actually made from coal tar anymore. Compounds like aniline (and its chemical precursor, benzine) are very, very bad for you. Were true coal tar dyes used in foods back in the day? Yes they were. However it must be said that while they were toxic and/or carcinogenic, they were far less dangerous than other dyes used at the time. The primary reason, because it took a lot less coal tar dye — just a few drops — to create a richly colored…whatever. And poison, as any toxicologist will tell you, is in the dose.

Today’s coal tar dyes are far, far safer than any of their predecessors. In fact as I mentioned in a previous post, they are about the safest, most exhaustively tested additives there are in the food industry. Some people don’t like them, some people are sensitive to them. For those people there quite a few natural alternatives to be found out there. I’m not necessarily advocating the use of synthetic colorings if you happen to be suspicious of them. Goodness knows that, at least historically speaking, there’s good reason to be suspicious. I however believe them to be quite safe indeed.