Planet Earth

Tea'd Off

By Jeffrey KlugerSep 1, 1994 5:00 AM


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If you're looking for a drink with a little grace, a little elegance, a little je ne sais quaff, you can't do much better than tea. Ever since the first member of high human society designed and built the first crude cucumber sandwich, tea has been the drink of refinement. Even its nomenclature is redolent of class. It's orange pekoe you enjoy with your scones, not Orange Crush; Earl Grey, not Earl Scruggs; oolong, not Sam-You-Made-the-Pants-Too-Long. For even the most casual tea drinker, the reminder is always there that this is a beverage of distinction.

There is, however, an embarrassing little problem with tea, and that problem is scum. As anyone who has stared blearily into a cup of China black while trying to get out of the house in time for the 6:13 can tell you, tea is not always the most pristine drink. Allow a bag or infuser to steep in water long enough, and a thin, barely visible film may float to the top. When the cup or pot is empty, the film can cling to the sides like grime in a bathtub. For years, tea fanciers have wondered about the source of the mysterious goo. Recently, however, the question ascended to the scientific plane when the esteemed journal Nature, which usually concerns itself with such weighty matters as genetics, cosmology, and paleontology, addressed the tea scum puzzle. Since last August, when British chemists submitted the prosaically titled letter "What causes scum on tea?" Nature's pages have been aboil with the question. In a scientific community with riddles of the universe to solve, it is tea that has moved to the front burner.

"Only if you know what scum is and how it forms," says British chemist Michael Spiro, "can you eliminate it. And tea drinkers do want it eliminated."

The recorded history of tea is a long one. The earliest known mention of the beverage dates to 350 B.C. in an ancient Chinese dictionary, the Erh Ya (not to be confused with a contemporary Hollywood dictionary, the Love Ya). Tea cultivation began in Szechuan province, eventually moving down the Yangtze River and out to the coast. The drink didn't make its debut in England for nearly 2,000 more years, when it was first sold at Garway's Coffee House in London in 1657. At the time, coffee was the beverage of choice in England, leading many people to suspect that even if the sun did set on the British Empire, nobody would be getting much sleep. Tea soon supplanted coffee as the national drink, resulting in a nation with a slightly lower median pulse rate and significantly better median breath.

Other milestones in the history of tea occurred in the late eighteenth century, when the British Parliament, led by King George Amin Dada, passed the Tea Act of 1773, which led to the Boston Tea Party and later to the Boston New Year's Eve Party and the Boston Red Sox vs. New York Mets World Series Party. In 1904 iced tea made its appearance at the St. Louis World's Fair when an English beverage salesman, Richard Blechynden, despaired of selling hot tea in hot weather and instead poured it over ice. (Blechynden's subsequent inventions--the cheese steak Dove Bar and the corn dog Slurpee--did not fare nearly so well.)

But all these steps down the slippery slope of tea history were coated in scum. "We've always known scum is there, but we've never known much more about it," says Spiro, of Imperial College of Science, Technology and Medicine, in London. "In normal brewing you get less than a milligram of scum, and since it's quite insoluble, you could consume all you wanted and it probably wouldn't hurt you. But it doesn't look very nice, and that's what people object to most."

It was in 1992 that Spiro and his colleagues at Imperial College were first approached by a major tea manufacturer wanting to know if they could figure out just what tea scum is so that the industry could figure out how to eliminate it. "When they came to us they made it clear they didn't want any publicity; they just wanted the scum taken care of," says Spiro, sounding less like a chemist than a Corleone.

But eliminating tea scum involves more than phoning Luca Brasi. Spiro and his collaborator, chemist Deogratius Jaganyi, brewed tea in beakers and then scooped the scum from them, washed it, dried it, and studied it under a scanning electron microscope. What they discovered was intriguing. About 15 percent of the scum was a white, flaky material that turned out to be calcium carbonate, and the rest was a complex organic material. While the discovery of mineral debris in a cup of Lipton would come as a surprise to the majority of tea drinkers, most of whom draw the line at a splash of half-and-half, it did not surprise Spiro. "The water we made the tea in was hard water," he explains, "as is much of the water in Great Britain. Hard water forms when underground springs run through beds of limestone and pick up calcium and bicarbonate."

Though the mineral ions are always present in groundwater, it takes a bit of doing for them to make themselves visible. When water is heated and tea is introduced into it, some of the organic compounds at the surface go through a series of reactions that involve the ions and oxygen in the air and are turned into a visible film. The calcium and bicarbonate ions form calcium carbonate, which gets mixed into the film as well, and voilà: scum.

When Spiro and Jaganyi reached their conclusions, they were under no illusions that a journal like Nature would leap to print them. In a publication whose taste in headlines usually runs toward the esoteric ("Velocities in the mantle," "Radial single-layer nanotubes") and away from the sensational ("Julia Roberts and radial single-layer nanotube to wed?"), a tea scum breakthrough would probably not command much attention. Nevertheless, the researchers submitted their work to the journal's Scientific Correspondence section, and no one was more surprised than they to find that their letter was actually published.

By the subdued standards of the Nature audience, the reaction to the letter was swift and passionate. A few months after Spiro and Jaganyi's correspondence appeared, marine botanist Ralph Lewin of the Scripps Institution of Oceanography, in La Jolla, California, weighed in with his own tea theories, saying, in so many words, "horsefeathers" (or "Equus caballus feathers"). According to Lewin's letter, which was published under the headline "Waxy tea," the scum is made up of nothing so elegant as ions, but rather, lipids that coat the leaves of tea plants and melt only at high temperatures. Plants use wax as a natural waterproofing to help maintain the proper level of internal moisture, and when tea leaves are processed, Lewin argued, the wax stays on; only when they are immersed in boiling water does it melt away and rise to the surface of the cup or pot, often cracking and fracturing like ice floes. When milk is added, the waxy film grows even thicker and more visible.

Other correspondence soon followed Lewin's. Jacinta Enzweiler and Marcelo de Oliveira, from the Universidade Estadual de Campinas in São Paulo, Brazil, added their voices to the rising scum chorus, agreeing with Spiro and Jaganyi and pointedly disputing Lewin. Spiro and Jaganyi, now joined by colleague Yuen Ying Chong, also took a run at Lewin, arguing that the wax theory holds no water, since it fails to explain why scum does not form in soft water containing no limestone residue, or why it does form when instant, powdered tea--which presumably contains no residual wax--is used.

Clearly the scum challenge had been issued, the goo gauntlet thrown. At the risk of becoming mired in the marsh of tea science myself, I figured the only way to settle the issue was to talk to some of the combatants directly.

My first effort to contact the tea scholars was less than successful. With the help of Brazilian directory assistance I was able to get the number of Drs. Enzweiler and Oliveira in São Paulo, but when I tried to phone, I repeatedly ran into problems. Most of the calls I made were apparently beamed out first to a relay station off the South American coast, then up to a satellite in geosynchronous orbit, and finally out to the vicinity of the Horsehead nebula. After several sprightly conversations with what appeared to be a pulsar, I gave up.

My luck was better when I tried to contact Spiro in London. Unlike one of his more famous namesakes, he was not, I discovered, prepared to plead nolo contendere in the tea wars.

"I don't understand what made Lewin say that scum is just bits of wax," he said. "He didn't do any experiments; he didn't look at it under a microscope; he just said off-the-cuff, 'Oh, I think that's what it is.' In our letter we stressed that we got scum only in hard water, which would seem to refute his wax theory."

Lewin, who was also readily reachable out at Scripps, was a little more accommodating. "I take no issue with what the other fellows said," he explained. "Their mechanism is correct, but so is mine; there's nothing that says both calcium carbonate and wax can't play a role." Lewin points out that the organic material isolated by Spiro and his colleagues had a molecular weight of 1,000, "which is precisely what you'd expect of high-melting-point wax. Even the question of instant tea isn't a problem. If the instant is made from tea leaves, it's likely that all of the components of the leaves--including wax--are going to be present in the resulting powder."

If the giants of tea science couldn't reach a consensus, the only answer, I figured, was to conduct a little research myself. Gathering up a few friends, I visited a restaurant promisingly named Tea & Sympathy. This out-of-the-way Manhattan bistro features authentic English tea and authentic English cuisine in an authentic English atmosphere. I must admit I would have been more enthusiastic about the outing had it not been for the authentic English cuisine part.

Britannia may rule the waves, but she's clearly abdicated in the kitchen. The secret to eating well in Great Britain is . . . well, there is no secret to eating well in Great Britain. Generally it's a good idea just to bring some crackers and Ring Dings with you and try to hold out until you get to France. Most British entrées belong to one of the four food groups--link sausage, patty sausage, pork sausage, and beef sausage--and bear such lip-smacking names as bangers and mash, bubble and squeak, toad in the hole, shepherd's pie, shepherd's household pets, and shepherd's extremely old footwear.

When my friends and I arrived at Tea & Sympathy, the bill of fare was not quite as forbidding as all that. The only item that initially alarmed me was Tweed kettle pie. The menu explained, however, that this was nothing more threatening than a salmon and cod casserole in a parsley sauce. (I did have a momentary flash of concern that the word parsley was supposed to be paisley, but one of my companions pointed out that this would clash with the tweed.) Ultimately I settled on Welsh rarebit--a sort of English version of a grilled cheese sandwich--while my more adventurous friends chose bangers and mash--a sort of English version of sausage and Spackle.

Of course, what we were really here for was not British food but British tea, and so in addition to our entrées we ordered two pots of brewed Typhoo, a popular blend of English black teas. We filled our cups and waited for scum to form, but the surface of our tea remained perfectly clear, without so much as a single ion of scum anywhere to be seen.

"Excuse me," I said to the waitress, feeling at least passingly ridiculous. "Do you normally get, well, scum on your tea?"

"Scum?" she asked, sounding more like Eliza Doolittle than I had any right to expect. "I think so. Let me ask. Constance!" she called across the restaurant. "Do we normally get scum?"

"Wha'? On the tea?" Constance called back, her own accent well- nigh impenetrable. "Nah. Not 'ere. Water's not 'ard enough. Get it back 'ome, though."

"So you think it's the hardness of the water that does it?" I asked, mentally scoring a run for Dr. Spiro.

"Don't know; could be."

"What about wax?"

"In the cup?"

"On the leaves."

"Never 'eard of it."

In our informal survey as well as in our cups, Dr. Lewin was clearly faring badly. New York may be a hard town, but it is known for soft water; if scum failed to form in water without calcium carbonate, it would have to be Spiro's ions, not Lewin's wax, that are responsible for the stuff in the first place. When we poured our second cups, however, the wax theory rallied. There on the surface of each cup was a faint, filmy sheen. Scum! In water as soft as a baby's bottom!

We drank off the Typhoo, I with a silent toast to Dr. Lewin, but then one of my more scientifically minded companions raised a question. Since we had all added milk to our first cups of tea, might some residual milk fat have been left behind, and might this be what we were seeing on the surface? We requested a clean cup, poured more Typhoo from the pot, and alas, my skeptical friend appeared right: there was not a scintilla of scum visible in the new, uncontaminated cup. This was not necessarily the death knell for the wax theory, of course; Lewin did stress that scum is more visible in the presence of milk. But the fact that it seemed utterly invisible without milk was not an encouraging sign.

We spent the better part of two hours and went through the better part of two more pots of tea trying to solve the scum mystery, but with no luck. By the end of our fourth (highly caffeinated) pot, as my heart rate became indistinguishable from a hummingbird's and my speech patterns indistinguishable from Porky Pig's, I figured it was time to call for our check. It was humbling but not surprising that working with nothing more than bangers, mash, rarebit, and Typhoo (when's the last time you used those four words in a sentence?), we had made less progress than scientists working with electron microscopes and mass spectrometers. Of course, unlike the scientists, we got to eat our research tools, so I suppose things all even out.

The scientists conducting the tea studies don't plan to pursue their work with much Manhattan Project-type vigor. Lewin has spoken his piece and appears content to move on to other, more substantive matters. Spiro and company have published their results in chemistry journals and are rounding out their research by looking into the effects of milk on tea scum. Whether their corporate sponsors will meanwhile try to develop the first-ever scumless tea is up to them. But there is one scum tip Spiro was willing to reveal to the world: If you add an acid to the tea water, you can turn the bicarbonate ions into carbon dioxide before they can form calcium carbonate. Without calcium carbonate, according to Spiro's theories, scum can't form. And one way to make tea water more acidic? Add a wedge of lemon. For this you need a Ph.D.?

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