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Groovy chemistry: The materials science behind records

From wax to vinyl, chemistry shaped the history of recorded sound

by Matt Davenport
June 13, 2016 | A version of this story appeared in Volume 94, Issue 24

An image shows a man who presses records inspecting a recently pressed LP.
Credit: Quality Record Pressings
Salstrom inspects a recently pressed vinyl record.

At Quality Record Pressings in Salina, Kan., the influx of orders for vinyl records has been so great that the staff has been turning away requests since September. This resurgence in vinyl’s popularity blindsided Gary Salstrom, the company’s general manger. The company is just five years old, but Salstrom has been making records for a living since 1979.

“I can’t tell you how surprised I am,” he says.

Listeners aren’t just demanding more records; they want to listen to more genres on vinyl. As most casual music consumers moved onto cassette tapes, compact discs, and then digital downloads over the past several decades, a small contingent of listeners obsessed with audio quality supported a modest market for certain musical styles on vinyl, notably classic jazz and orchestral recordings.

Watch this process from start to finish for the QRP creation of the Cat Stevens classic “Tea for the Tillerman.”
Credit: Quality Record Pressings
Watch this process from start to finish for the QRP creation of the Cat Stevens classic “Tea for the Tillerman.”
Credit: Quality Record Pressings

Now, seemingly everything else in the musical world is getting pressed as well. The Recording Industry Association of America reported that vinyl record sales in 2015 exceeded $400 million in the U.S. That figure is vinyl’s highest since 1988, and it beat out revenue from ad-supported online music streaming, such as the free version of Spotify.

While old-school audiophiles and a new wave of record collectors are supporting vinyl’s second coming, scientists are looking at the chemistry of materials that carry and have carried sounds in their grooves over time. They hope that in doing so, they will improve their ability to create and preserve these records.

Eric B. Monroe, a chemist at the Library of Congress, is studying the composition of one of those materials, wax cylinders, to find out how they age and degrade. To help with that, he is examining a story of litigation and skulduggery.

In 1905, Thomas Edison was the defendant in a lawsuit over the composition of wax cylinders used as recording media. Several inventions in recording predate these cylinders, but the 1905 lawsuit reveals many of the key considerations in developing quality materials for an emerging record industry.

Making the record

Gary Salstrom started pressing records in 1979, and the methodology hasn’t changed much since then. In fact, the process still shares the same basic principles Thomas Edison and others used to press grooves into disc-shaped records in the early-20th century. Salstrom, the general manager at Quality Record Pressings, or QRP, walks C&EN through the current process.

1. Cutting

At a mastering facility somewhere around the world, an audio engineer mounts a 35.6-cm polished aluminum disc coated with nitrocellulose lacquer onto a lathe. The engineer then plays back a studio recording—for instance, from a reel of magnetic tape—which drives the lathe’s sapphire cutter vertically and horizontally to carve a groove in the lacquer, creating a master disc. These nitrocellulose masters are sometimes called acetate discs in the business, but that’s a material misnomer.

2. Plating

The mastering facility ships the nitrocellulose to Salstrom and his team of about 60, who start the next step within a day of receiving the disc. The grooves can start to deform if they wait much longer—not a lot, but enough that a trained ear can hear the degradation. The lacquer disc first gets a bath of stannous chloride to prepare it to hold onto a spray coating of silver. Once the lacquer has its silver coat, QRP electroplates it with nickel to create a metal disc that is essentially a negative of the lacquer disc—with its groove facing outward, instead of inward. Starting with this nickel negative, QRP uses a similar plating method to create a nickel double negative: a grooved metal disc that should replicate the groove in the lacquer. This is called the mother, and it is playable, allowing the QRP team to check how well it reproduced the nitrocellulose master. Once the team is satisfied with the fidelity of this disc, the team starts another plating process using the mother to produce metal stampers.

3. Pressing

Two stampers—one for the top and one for the bottom of a record—are loaded into a press, which is connected to a hopper filled with polyvinyl chloride pellets. The press melts the PVC pellets by passing them through a tube surrounded by steam. The now-molten polymer is then sandwiched between the stampers. Steam courses through channels adjacent to the stampers during pressing to ensure the PVC remains fluid and can really get into the grooves. Water then floods the channels, cooling and hardening the polymer. “If you didn’t cool it, you’d be left with a goopy mess,” Salstrom explains. The hardened disc then slips down to the next stage of the machine, where a trimmer blade slices off the excess vinyl. Finally, the press sends the record to a spindle, where it’s allowed to further cool overnight.

The waxes in question are more accurately described as metal soaps, fatty acid chains stuck together with the help of metal ions. A stylus can glide over the soft soaps without hitting hard bumps or grains that would produce audible crackles and pops. Yet the materials are substantial enough to maintain their grooves after being played repeatedly.

Although wax cylinders may seem like a primitive storage medium, they were a revelation at the time. Edison invented the phonograph in 1877 using cylinders wrapped in tinfoil, but he shelved the project to work on the lightbulb, according to sources at the Library of Congress.

But Edison was lured back into the audio game after Alexander Graham Bell and his Volta Laboratory had created wax cylinders. Working with chemist Jonas Aylsworth, Edison soon developed a superior brown wax for recording cylinders.

“From an industrial viewpoint, the material is beautiful,” Monroe says. He started working on this history project in September but, before that, was working at the specialty chemical firm Milliken & Co., giving him a unique industrial viewpoint of the material.

“It’s rather minimalist. It’s just good enough for what it needs to be,” he says. “It’s not overengineered.” There was one looming problem with the beautiful brown wax, though: Edison and Aylsworth never patented it.

Enter Thomas H. MacDonald of American Graphophone Co., who basically paid people off to help him copy Edison’s recipe, Monroe says. MacDonald then filed for a patent on the brown wax in 1898. But the lawsuit didn’t come until after Edison and Aylsworth introduced a new and improved black wax.

To record sound into brown wax cylinders, each one had to be individually grooved with a cutting stylus. But the black wax could be cast into grooved molds, allowing for mass production of records.

Unfortunately for Edison and Aylsworth, the black wax was a direct chemical descendant of the brown wax that legally belonged to American Graphophone, so American Graphophone sued Edison’s National Phonograph Co. Fortunately for the defendants, Aylsworth’s lab notebooks showed that Team Edison had, in fact, developed the brown wax first. The companies eventually settled out of court.

Monroe has been able to study legal depositions from the suit and Aylsworth’s notebooks thanks to the Thomas A. Edison Papers Project at Rutgers University, which is working to make more than 5 million pages of documents related to Edison publicly accessible.

Using these documents, Monroe is tracking how Aylsworth and his colleagues developed waxes and gaining a better understanding of the decisions behind the materials’ chemical design. For instance, in an early experiment, Aylsworth made a soap using sodium hydroxide and industrial stearic acid. At the time, industrial-grade stearic acid was a roughly 1:1 mixture of stearic acid and palmitic acid, two fatty acids that differ by two carbon atoms.

That early soap was “almost perfection,” Aylsworth remarked in his notebook. But after a few days, the surface showed signs of crystallization and records made with it started sounding scratchy. So Aylsworth added aluminum to the mix and found the right combination of “the good, the bad, and the necessary” features of all the ingredients, Monroe explains.

The mix of stearic acid and palmitic is soft, but too much of it makes for a weak wax. Adding sodium stearate adds some toughness, but it’s also responsible for the crystallization problem. The aluminum stearate prevents the sodium stearate from crystallizing while also adding some extra toughness.

In fact, this wax was a little too tough for Aylsworth’s liking. To soften the wax, he added another fatty acid, oleic acid. But a majority of these cylinders started sweating when summertime rolled around—they exuded moisture trapped from the humid air—and were recalled. Aylsworth then swapped out the oleic acid for a simple hydrocarbon wax, ceresin. Like oleic acid, it softened the wax. Unlike oleic acid, it added an important waterproofing element.

And so went the soapy song and dance. Aylsworth continued revising formulations and procedures as he and Edison discovered problems.

But Monroe hasn’t just been reading about these formulations. “I’m a chemist with a hood,” he says. “I’m gonna make me some.”

By performing historical chemical reenactments, Monroe can compare his samples to the wax cylinders in the Library of Congress collection to understand how the material ages and how to better preserve it. He can use his materials to quantify things such as a metal soap’s hardness or its thermal expansion coefficient without touching an invaluable collection piece.

Credit: Anna-Maria Manuel
A cylinder made from Edison’s brown wax, which is actually more of a metal soap.
A photograph shows an early brown wax cylinder made by Thomas Edison’s company.
Credit: Anna-Maria Manuel
A cylinder made from Edison’s brown wax, which is actually more of a metal soap.

Monroe has been performing chemical analyses on both collection pieces and his synthesized samples to ensure the materials are the same and that the conclusions he draws from testing his materials are legit. For instance, he can check the organic content of a wax using techniques such as mass spectrometry and identify the metals in a sample with X-ray fluorescence.

Monroe revealed the first results from these analyses last month at a conference hosted by the Association for Recorded Sound Collections, or ARSC. Although his first two attempts to make brown wax were too crystalline—his stearic acid was too pure and had no palmitic acid in it—he’s now making substances that are almost identical to Edison’s.

His experiments also suggest that these metal soaps expand and contract quite a bit with changing temperatures. Institutions that preserve wax cylinders, such as universities and libraries, usually store their collections at about 10 °C. Instead of bringing the cylinders from cold storage directly to room temperature, which is the common current practice, preservationists should allow the cylinders to warm gradually, Monroe says. This will minimize the stress on the wax and reduce the probability that it will fracture, he adds.

The similarity between the original brown wax and Monroe’s brown wax also suggests that the material degrades very slowly, which is great news for people such as Peter Alyea, Monroe’s colleague at the Library of Congress.

Alyea wants to recover the information stored in the cylinders’ grooves without playing them. To do so he captures and analyzes microphotographs of the grooves, a strategy pioneered by researchers at Lawrence Berkeley National Laboratory.

Soft wax cylinders were great for recording one-off sessions, Alyea says. Business folks could capture dictations using wax and did so up into the 1960s. Anthropologists also brought the wax into the field to record and preserve the voices and stories of vanishing native tribes.

“There are 10,000 cylinders with recordings of Native Americans in our collection,” Alyea says. “They’re basically invaluable.” Having those recordings captured in a material that appears to stand up to time—when stored and handled properly—may seem like a stroke of fortune, but it’s not so surprising considering the material’s progenitor.

“Edison was the engineer’s engineer,” Alyea says. The changes he and Aylsworth made to their formulations always served a purpose: to make their cylinders heartier, longer playing, or higher fidelity. These considerations and the corresponding advances in formulations led to his second-generation moldable black wax and eventually to Blue Amberol Records, which were cylinders made with blue celluloid plastic instead of wax.

But if these cylinders were so great, why did the record industry switch to flat platters? It’s easier to store more flat records in less space, Alyea explains.

Emile Berliner, inventor of the gramophone, introduced disc-shaped gramophone records pressed in celluloid and hard rubber around 1890, says Bill Klinger. Klinger is the chair of the Cylinder Subcommittee for ARSC and had encouraged the Library of Congress to start the metal soaps project Monroe is working on.

In 1895, Berliner introduced discs based on shellac, a resin secreted by female lac bugs, that would become a record industry staple for decades. Berliner’s discs used a mixture of shellac, clay and cotton fibers, and some carbon black for color, Klinger says. Record makers manufactured millions of discs using this brittle and relatively inexpensive material.

“Shellac records dominated the industry from 1912 to 1952,” Klinger says. Many of these discs are now known as 78s because of their playback speed of 78 revolutions-per-minute, give or take a few rpm.

PVC has enough structural fortitude to support a groove and stand up to a record needle.

Edison and Aylsworth also stepped up the chemistry of disc records with a material known as Condensite in 1912. “I think that is by far the most impressive chemistry of the early recording industry,” Klinger says. “By comparison, the competing shellac technology was always crude.”

Klinger says Aylsworth spent years developing Condensite, a phenol-formaldehyde resin that was similar to Bakelite, which was recognized as the world’s first synthetic plastic by the American Chemical Society, C&EN’s publisher.

What set Condensite apart, though, was hexamethylenetetramine. Aylsworth added the compound to Condensite to prevent water vapor from forming during the high-temperature molding process, which deformed a disc’s surface, Klinger explains.

Edison was literally using a ton of Condensite per day in 1914, but the material never supplanted shellac, largely because Edison’s superior product came with a substantially higher price tag, Klinger says. Edison stopped producing records in 1929.

But when Columbia Records released vinyl long-playing records, or LPs, in 1948, shellac’s days in the music industry were numbered. Polyvinyl chloride (PVC) records provide a quieter surface, store more music, and are far less brittle than shellac discs, Klinger says.

Lon J. Mathias, a polymer chemist and professor emeritus at the University of Southern Mississippi, offers another reason for why vinyl came to dominate records. “It’s cheap, and it’s easily molded,” he says. Although he can’t speak to the specific composition of today’s vinyl, he does share some general insights into the plastic.

PVC is mostly amorphous, but by a happy accident of the free-radical-mediated reactions that build polymer chains from smaller subunits, the material is 10 to 20% crystalline, Mathias says. As a result, PVC has enough structural fortitude to support a groove and stand up to a record needle without compromising smoothness.

Without any additives, PVC is clear-ish, Mathias says, so record vinyl needs something like carbon black to give it its famous black finish.


Finally, if Mathias was choosing a polymer to use for records and money was no object, he’d go with polyimides. These materials have better thermal stability than vinyl, which has been known to warp when left in cars on sunny days. Polyimides can also reproduce grooves better and offer a more frictionless surface, Mathias adds.

But chemists are still tweaking and improving vinyl’s formulation, says Salstrom of Quality Record Pressings. He’s working with his vinyl supplier to find a PVC composition that’s optimized for thicker, heavier records with deeper grooves to give listeners a sturdier, higher quality product. Although Salstrom may be surprised by the resurgence in vinyl, he’s not looking to give anyone any reasons to stop listening.  

Keeping clean with a little 15

A soft brush can usually handle any dust that settles on a vinyl record. But how can listeners deal with more tenacious dirt and grime?

The Library of Congress shares a recipe for a cleaning solution of 2 mL of Dow Chemical’s Tergitol 15-S-7 in 4 L of deionized water. C&EN spoke with Paula Cameron, a technical service manager with Dow, to learn about the chemistry that helps the Tergitol surfactant get into—and out of—the groove.

Molecules in Tergitol 15-S-7 possess hydrophobic hydrocarbon chains that are between 11 and 15 carbon atoms long. The S means it’s a secondary alcohol, so there’s a hydroxyl jutting from the midsection of the hydrocarbon chain to connect it to a hydrophilic chain of repeating ethylene oxide units.

Finally, the 7 is a measure of how many moles of ethylene oxide are in the surfactant. The greater the number, the more water-soluble the compound is. Seven is squarely in the water-soluble category, Cameron says. Furthermore, she adds, the surfactant doesn’t become viscous or gel-like when mixed with water.

The end result is a mild, fast-rinsing surfactant that can get in and out of grooves quickly, Cameron explains. The bad news for vinyl audiophiles who might want to try this at home is that Dow typically doesn’t sell surfactants directly to consumers. Their customers are generally companies who make cleaning products.

Sadly Cameron doesn’t know of a consumer product that has similar properties. And the Library of Congress doesn’t guarantee this solution will satisfy all users.


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