And then there were the IC spray machines. There were seven of them, each capable of spraying 320 cans per minute. Overhead, a conveyer belt delivered cans into seven large funnels, and from these the cans dropped, one at a time, into the glass chambers of the machines. As each can dropped, it was loaded onto an indexed wheel, which rotated, stopped, rotated, stopped. As the wheel rotated, the can spun rapidly at 2,200 revolutions per minute. For an instant, each can was a veritable figure skater doing triple lutzes. At the first position, a high-pressure injector sprayed liquid epoxy down into the can. At the second, another injector sprayed the liquid epoxy at a slight angle, toward the top of the wall. This was to get an even, consistent coating. On the walls of the chambers, atomized spray accumulated like fine snow and formed a white, lard-like goop. An employee was scraping one clean with a metal spatula, much as one scrapes frost from a windshield.
And then, in a fraction of a second, the cans were gone. A conveyer belt whisked them away to another oven, which cured the epoxy by heating it up to 390 degrees, gradually, for two minutes.
Beyond the oven and some fans and the waxing machine and the necker and the flanger, Ball had a few machines and workers examining cans, to be sure they had been coated properly—in other words, thoroughly. Five digital black-and-white cameras examined the coating inside every can, with a strobe. One camera pointed straight down, while four pointed at the neck, where the end would eventually be fastened. A computer assessed the gray scale of every can—at two thousand cans per minute—to determine if the coating was sufficient, which is to say perfect. Another test employed a light sensor to test for holes in every can. The tiniest pinhole could spell disaster: a leaker or an exploder.
Line workers also collected sample cans, to test the internal coating more precisely. Hourly, they filled these samples with an electrolyte and then measured its current (in milliamps). If the coating wasn’t perfect, the electrolyte would come into contact with the aluminum, electrons would start to migrate, and the measurement would not read zero. They call this a metal exposure test. Line workers also tested the coating with two adhesion tests. In one, they measured how much force it took to scratch through the coating. In the other, they scratched the coating, then slapped sticky tape on the wound and pulled it off, and measured how much coating had been removed.
When things go wrong with the IC sprayers, apparently, it’s usually obvious. The injectors rarely execute partial sprays; they either fail to spray, or spray too much, and then the coating doesn’t cure right. If the can isn’t clean or still has lubricant on it, the coating doesn’t stick. If the oven settings are off, and the coating heats up too fast, blisters form. Unlucky customers have found, in their sodas, the internal coating floating on the surface. I’d take that over a mouse any day.
Finally, the cans were stacked in imposing pallets. A pallet of 8,169 cans is nine feet tall. They’re stacked two, three, four high in a warehouse that, with thirty-foot doors, outdoes all other warehouses except airplane hangars. You could fit a house through its front door.
The world’s first cans, developed by an Englishman in 1810, owed their corrosion resistance to a layer of tin. It didn’t hurt that the tin canisters were a fifth of an inch thick, and weighed over a pound. It was one of America’s first can makers, a Londoner who sailed to Boston named William Underwood, who is responsible for the shortened word that we know today. While he was sterilizing (pasteurizing) tin canisters of lobster in a giant iron kettle on the beach in Harpswell, Maine, one of his bookkeepers shortened the word canister—from the Greek kanastron, “a basket of reeds”—to can.
The art of can making entailed so much trial and error that early cans weren’t reliable. They exploded. They exploded because can makers didn’t like sterilizing their cans. Boiling them in water made them rust. That’s why some canners afterward slathered their cans with lead paint or lacquers. And still they went bad. Unlucky canners lost 100 percent of their production; lucky ones dumped thousands of errors in the Erie Canal. Some warned dealers to test their cans before selling any. A Wisconsin canner of peas, who quartered in the second floor of his warehouse, lost sleep on account of all the cans of peas exploding below him. Bacteria were to blame, and a young professor of bacteriology at the University of Wisconsin named Harry Russell studied and solved the problem for the pea canner in 1894. Can making had finally turned scientific.
In the meantime, can makers had begun using tin plate coated with enamel, which allowed them to can applesauce, sardines, and tomatoes (without juice). Then something funny happened. A Maryland canner complained about black spots in his cans of corn. He figured the tin plating was no good. Herbert Baker, the chief chemist at the American Can Company’s lab, figured him wrong. He showed that “corn black” was iron sulfide, the iron from the can and the sulfide from the corn. He also showed that zinc prevented its formation. Zinc had been in the solder used in old handmade cans. New solder, and new machine-made cans, didn’t contain any zinc.
From 1911 to 1922, Baker worked on getting zinc back into cans. First, he looked at the thickness of tin, and the purity of the steel, but these were dead ends. Then he impregnated parchment paper with zinc oxide, and lined cans with it, which was effective but inefficient. Galvanized ends worked, too, but imparted upon foods a zinc flavor. Finally, Dr. G. S. Bohart, chemist at the National Canners Association, put zinc oxide in enamel.
Like modern epoxy coatings, enamels separated the package from the product. Can makers had learned the hard way that a plain tin-lined can was fine for pastas, peaches, pears, and pineapples, but would bleach strawberries, cherries, and beets so thoroughly that customers wouldn’t return to buy more. Peas, any kid knew, were mild, but beans, which contained sulfur, would turn blue, then black. Bohart’s C enamel (as opposed to the standard R enamel) worked because the zinc oxide reacted with the hydrogen sulfide before it had a chance to react with the can. C enamel allowed can makers to put all kinds of heretofore forbidden—that is, corrosive—products in cans. Can making companies quickly figured out how to put ham, dog food, and orange juice in cans. Aggressive foods, such as sauerkraut, pickles, and jalapenos, would eventually demand even thicker coatings.
Still, nobody could figure out how to can beer. Tin-coated steel cans turned beer cloudy, and ruined its taste. Iron was even worse: just one part per million of iron in beer ruined its flavor. This was because of iron’s interaction with water: it tears water molecules apart, releasing oxygen that changes the taste of the beer, and corrodes the can. C enamel wasn’t cutting it. Brewer’s pitch, as sticky as tar, seemed a good coating candidate, except that it didn’t survive pasteurization. The solution was two different coats of enamel—one made by Union Carbide, and the other made by a small company that became Valspar. In 1935, after three years of effort, American produced the world’s first beer can. Gottfried Krueger Brewing, of Newark, New Jersey, was American’s first customer. Pabst got into the game six months later. By the end of the year, can makers had sold more than two hundred million steel cans to twenty-three brewers.
By the time Bill Coors, an engineer, borrowed a quarter million dollars and set out to manufacture aluminum cans, in 1954, he could turn to epoxy rather than enamel to protect the metal. He could also turn to the work of an English scientist, Denis Dickinson, who in 1943 had made a stab at quantifying the corrosivity of the stuff in a can. He called his measure a corrosivity index. To compute it, he took a two-inch strip of a can, boiled it in hydrochloric acid for two minutes, and measured how much metal had been lost. Usually it was somewhere between 100 milligrams and 300 milligrams. Then he took the same strip of metal, put it in a food or beverage for three days, at 77 degrees, and measured how much more metal had been lost. A product’s corrosivity index was the ratio between metal lost to food and metal lost to acid. Most products came out below 1. Fruits came out anywhere from 2 to 4. Anything above 6, Dickinson figured, was abnormally corrosive. Yet he remained unhappy with his measure. “It is unfortunate th
at this, probably the most important diagnostic factor,” he wrote, “is still so imperfectly understood.” He’d have loved Ed Laperle and been fascinated by Mountain Dew.
Whatever the constitution of his energy drink, Bob doesn’t just put it in one of Ball’s cans and close it. He must deal with the headspace: the 5 milliliter air bubble at the top. He doesn’t want oxygen in there, because oxygen trapped there will dissolve in the beverage and corrode the can. If what’s on the inside of the can gets on the outside, terrible things happen. In a warehouse as in a hospital, just one untreated infection can be enough to infect every patient in the building.
Bob deals with this threat by flooding the headspace with carbon dioxide or nitrogen before seaming the can shut. If he doesn’t, he voids the warranty on the can, exposing himself to all kinds of liability. Because this final step happens at a beverage plant, not at Ball’s can-making plant, Ball assists. The guy who oversees is Dave Scheuerman. A dozen reps work for him, running around North America, enlightening customers on “double seam theory,” teaching them how to read good cans, recommending pressurizers and optical oxygen sensors, helping them properly put their product in cans. Scheuerman has been working at Ball for thirty years and has seen a lot of good cans perish in the line of duty. He tells their tales somberly, soberly, and slowly. I met him on the third day of Can School, and of all the engineers I met, he was my favorite. A trained food biologist, he seemed more like a general in the Ministry of Can Defense. With an undershirt poking out beneath a blue shirt and jacket, he looked not unlike a tubbier Robert Redford. He knows that even with all the technique in the world, there’s still room for error. “It’s a talent,” Scheuerman said. “An art form you have to learn.”
The simplest mistake the filler at a beverage manufacturer can make is one of overcompensation. A filler may crank up the nitrogen or carbon dioxide and overpressurize his cans. Other beverage manufacturers play it safe by overfilling their cans, selling 12.2 or more ounces of beer for the price of 12 ounces. This is not a rookie mistake. Scheuerman has done the math, evaluated engineering tolerances, and calculated with assurance that a manufacturer who decreases his fill range one twentieth of an ounce—from 12.1 to 12.05 ounces—will save 174 cases, or 4,176 cans for every million cans he produces. Fewer of his cans will explode. It’s technically 0.4 percent of his inventory, constituting a few thousand dollars’ worth of product that he was giving away for free by overfilling, and enough product to fill 17 more cans. It pays for itself: no destroyed products, no threats to other perfectly good products, no wasted time, no complaints, no lawsuits. “If they have too many duds,” Scheuerman said, “I just tell ’em, back off on your fills.”
Sometimes duds manifest themselves on account of small changes in the way a particular beverage is made. A new fertilizer turns out to be corrosive, an ink turns out to release lead, a new coating turns out to produce traces of benzene, or a lemon-lime extract, imported from Brazil, turns out to have been boiled in a copper kettle. Some copper ends up in solution, and once in the can, together with acid, corrodes it galvanically (recall the Statue of Liberty). The can plates out, and the plating removes more of the internal coating, and the bare aluminum only exacerbates the effect. Copper can also come from the water supply, the water that is added to soda syrup. “You don’t even need a microscope,” Scheuerman said, describing the symptoms of copper contamination in cans. “You see black dots all over the can. You see a reddish copper tinge.”
Overgassing, overfilling, and unwittingly contaminating cans are of such concern to Scheuerman because two out of three leaking product complaints now come from warehouse problems. This is the dreaded outside-in corrosion. Scheuerman laid out the scenario: a primary leaker leads to secondary leakers and in not much time the distributor of Bob’s Energy Drink is facing an unfolding nightmare. “You get a leak in a can at the top of the case,” Scheuerman said. “The can leaks, drips down, wicks into adjacent cases. You end up with a Christmas tree pallet.” He paused. “I have seen entire warehouses, with a million cases, that were a total write-off.” On the podium at Can School, he said this seriously, like it might pain attendees to imagine. Rocking back and forth on his feet—heels, toes, heels, toes—he said calmly, “This is not a salvage operation.”
Hot warehouses are particularly terrifying to Scheuerman. In such places, the alloy used to make the ends “relaxes,” or loses 7 percent of its strength. So warehouses in Alaska are safe. Warehouses in Alabama are risky. A 115-degree shelf is a problem; a 150-degree trunk—like Lynda Ryan’s—is definitely a problem. Hence the disproportionate number of failures from the South. Worse, shrink-wrapped pallets, in hot and humid warehouses, tend to collect and trap condensation at the can’s most vulnerable spot, the top. Technically, there’s no coating on the top of the score mark around the aperture, so if water collects there, you get top-down corrosion, and leakers, and then more corrosion problems. (Food cans sometimes rust via the labels, which absorb moisture.) So Scheuerman recommends using shrink-wrap with slits in it. Otherwise, he said, truck drivers delivering cans will hear pops in their trucks. “The sad thing is,” Scheuerman said, “they always ask, ‘Is this safe to send to the customer?’ I don’t know. More may pop next week.” He says a fan is okay, but what distributors really ought to do, ironically, is keep the product warm—warmer than the dew point.
Scheuerman learned most of this fifteen years ago, when Ball started printing 1-800 numbers on cans, and people called with problems. “We figured, of all the places our cans go, supermarkets, gas stations, and convenience stores, that the last two were where the problems are.” He was wrong. Most consumer complaints were coming from supermarkets. Next in line was vending machines. He wondered: how can the claims be so high? It turned out they’d find a leaker, wipe the others off, and put them back. “They were spreading a cancer,” Scheuerman said. “In vending machines,” he said, “if they act quick, they get away with it. If not, they gotta replace the whole machine and clean it.” He said all of this with a tone that would not be inappropriate at a wake. His face remained straight.
“When a customer picks up a can and it’s dented, banged up, corroded, or leaky, they usually don’t say, ‘Boy, Safeway beat the heck out of this,’ or, ‘the Freightway Truck Line abused this.’ They look at it and they say, ‘I can’t believe these people put this on the market, on the shelf.’ ” Ball doesn’t like it when that happens. So Scheuerman gives customers corrosion bulletins and displays. And he has a road-ready presentation. He can do it anywhere. All he needs to know is the number of people he’s presenting to, and what language to do it in. Calmly, steadily, Scheuerman balances defense with offense. From lessons learned in the field, he suggests modifications that increase efficiency and reduce the chances that a canner will be exposed to a lawsuit from a can that explodes and takes someone’s eye out.
Still, cans fail. Ball implores customers to notify them ASAP if they have any complaints of leakers, and compiles the responses in a report. They want to perform a “root cause analysis” on all field failures they can get their hands on. During Can School, Laperle showed me where they do this. It’s called “the morgue,” and it was a small room near the flavor lab where thirteen cans, dead of various causes, lay exposed on a black countertop.
It’s Laperle’s task to determine if the fault of these field failures lies with Ball or not. Sometimes, a canner or distributor or consumer sends a can back because of an unidentifiable blob. This is not a problem. About a third of the lab contains machinery devoted to solving such a mystery. There’s a Fourier Transform Infrared Spectroscope, which checks the composition of the blob against a database of 100,000 chemicals, and a gas chromatograph, which checks a database of even more. The blob could be lubricant, or ink, or any other number of manufacturing chemicals, or it could be something the filler goofed on, like something from a truck, or a pallet, or it could be bird poop, or part of a mouse, or alfalfa pollen, which has turned beer the color of Mountain De
w.
To be sure it’s not an impurity in the metal, there’s an electron microscope in a room next door. With this, employees like Michelle Atwood, a young Midwestern biochemist, examine the crystal structure of the metal in the can, looking for globs of iron, for example. When I poked in the room, Atwood zoomed in on the tiny back-to-back Rs incised into the tab of a Rockstar Energy Drink can. She zoomed from 100x, to 500x, to 1000x, until the backbones of the Rs looked jagged, like thorny spines of a rose bush.
Often the fault lies with customers who unintentionally discover the weakest point of the can. These customers tend to be old, and they tend to winter in Florida. In March, these snowbirds buy cases of soda, put them in the closets of their trailers, and drive north. In October, when they head south again, they open the closet door to a swarm of fruit flies. One or more of the cans have burst. This happens regularly, every fall: perfectly made, perfectly filled, perfectly warehoused cans fail.
The cans fail because the ends—which are manufactured on a separate line at the Golden plant and get shipped to canners in brown paper bags, like huge packages of Ritz crackers—are more susceptible to corrosion than any other part of the can. To make a can openable, the aperture must be scored such that kid fingers and elderly fingers can lift up on the tab and tear the aperture. The score line is only 1/1000 of an inch thick, and technically it’s not coated. The die that forms the score is so sharp, and so forceful, that the coating right at the score line is removed. To be sure the scores are just right, they’re camera and pressure tested at the Golden plant. “Just right” is an understatement. “Give or take two or three millionths of an inch,” Elmer, the plant’s assistant manager, once told me while pointing to a can, “and this can won’t open.” Elmer grew up in Missouri, making parts at his father’s machine shop. The parts were for the aerospace industry. Cans, he explained, are manufactured with much tighter tolerances than aerospace parts—ends particularly. Many in the industry like to say, he told me, “The can is just a pedestal on which the crown sits.” Marvel of marvels: not perfect-tasting beer but the top of the can.
Rust: The Longest War Page 12
