Tire technology has come a long way since the Ford Model T first rolled out of the factory in 1908. Modern tires are not only different in dimension, compound, and overall structure, but they're also a different colour. That's because early tires were white, and only around World War I did they turn black. Here's why.
I suppose I should say what started me down this path, as tire colour probably isn't something anyone thinks about much. When my dad came to visit Detroit back in March, I took him to the Ford Piquette Avenue Plant Museum, the first Ford-owned factory, and the hallowed spot where the Model T was conceived and initially assembled.
While there, I noticed that certain Model Ts had white tires, while others had wheels wrapped in black rubber like we're used to seeing today. So, keen to learn more, I got in touch with tire manufacturer Michelin.
"Original tires had a lighter shade because of the natural colour of rubber," a company representative told me. "Carbon black [a fine manufactured soot] was added to the rubber compound in [circa 1917] and produced a tenfold increase in wear resistance."
This increased longevity is confirmed by award-winning chemical engineer Jack Koenig, who says in his book Spectroscopy of Polymers that a tire without carbon black would last "less than 8047km." Consider that most tires are driven between 12,000 and 24,140km a year, and are meant to last three or four years or more, and you get how low that was.
The Michelin spokesperson went on, saying carbon black represents about a quarter to 30 per cent of the composition of the rubber used in tires today, and in addition to making them more wear resistant, the material that gives tires their black colour is also good at protecting tires against ultraviolet rays that can cause cracking, and it also improves grip and general road handling.
Tire company Coker also gives credit for tires' black appearance to carbon black in a blog post titled "The History and Timeline of Whitewall Tires", mentioning that the strengthening properties of carbon black is key. Goodyear's Hug the Road blog also mentions improved resistance to ozone and increased conductivity to help transfer heat away from the tread and belts as benefits key to the blackening material.
So now it's worth asking:
What Is Carbon Black?
Carbon black is the product of a hydrocarbon that has gone through incomplete combustion, and whose "smoke" has been captured as fine black particles consisting almost entirely of elemental carbon.
It has been manufactured in a number of different ways over the years. According to carbon black manufacturer Orion Engineered Carbons, one of the oldest processes involves allowing a flame from an oil lamp to impinge upon a cool surface, and for the resulting powdery soot from that surface to be scraped off. That powdery soot was called lampblack, and was used as ink has for many centuries.
But in the 1870s, as noted in the thrilling tome Developments in Rubber Technology, Volume 1, came a breakthrough called the channel process. Essentially, it involved burning natural gas up against water-cooled H-shaped metal channels, and collecting the carbon deposits. This new process, and specifically the finer particles it yielded, was apparently an important step in yielding stronger tires for the auto industry, as Orion Engineered Carbons writes in its brochure:
The finer particles obtained from Channel Black made it possible to increase tire longevity to several tens of thousands of miles. In retrospect, the automotive industry owes much of its rapid growth to the discovery and refinement of Channel Black production.
But channel black wasn't particularly efficient or environmentally friendly, as you can see in the below picture of the stuff getting made. These were called "hot houses", and their smoke could be seen for kilometres.
Today, the primary method of obtaining carbon black is called the "furnace process", which involves taking a heavy oil or natural gas feedstock, and injecting it into a furnace wherein natural gas and pre-heated air have combusted (see image below). The high temperatures of this reaction cause the feedstock to "crack" and turn into smoke, which is cooled by water and filtered out as tiny carbon black bits from the gas.
The resulting fine powder is then formed into pellets via water and a binding agent for easier handling and transport.
Carbon black powder is extremely fine, and to see the true shape of the material requires use of an electron microscope, which reveals tiny particles, generally between 10 nanometres and 500 nanometres, that have fused together into chains of various shapes.
According to major carbon black manufacturer Birla Carbon, the size of the particles, as well as that of the fused-together "aggregates," and overall shape affects things like a rubber's abrasion resistance, tensile strength, blackness, conductivity, and weather-ability.
Different grades of carbon black tend to be categorised based on their surface area, as well as on their effect on the cure rate of rubber. Here's a look at a number of different grades, which are used for a variety of different rubber applications like motor mounts, conveyor belts, and high performance tires.
How a World War I Supply Shortage Could Be The Reason for Black Tires
The history of how tires got their black colour is complex and fascinating, but also a bit murky. I spoke with Jack Seavitt, a member of the board of trustees and also a tour guide at the Ford Piquette plant. While he later admitted that he and his colleagues had different stories on how it all went down, his take was that tires may have turned black as a result of a World War I munitions shortage.
In particular, he said that in the early 1900s, tire makers figured out that they could add magnesium oxide to rubber to increase strength. "But magnesium oxide was needed in the munitions industry during World War I," he told me, saying it was used as a propellant, and that brass for artillery shells was also in short supply. "So they said to the automotive industry: You can't use brass anymore, and you can't use magnesium oxide in tires."
"So they were told to find something else, and the something else they found was carbon black."
Clearly unsure about his account, Seavitt told me he and his team would do some more fact checking, and while I still haven't heard back, Seavitt's story did inspire me to do a bit more digging on the influence of World War I on black tires. And what I found is that he seems to be partly right.
A bit of browsing on the internet brought me to Crayola, makers of crayons and markers. Crayola used to be a brand under the company Binney & Smith, named after Edwin Binney and C. Harold Smith. These two were the son and nephew, respectively, of Joseph Binney, founder of New York-based Peekskill Chemical Works, which sold charcoal and lampblack — the aforementioned deep black powder obtained by collecting soot deposits from burning oil. It was used to make pigments and inks.
After Joseph retired and Edwin and C. Harold started Binney & Smith, the company became known for red oxide paint, which was used to decorate barns throughout America, and after the turn of the century, Binney & Smith introduced innovations like dustless chalk for classrooms and affordable crayons branded "Crayola." More importantly, by this time, Binney & Smith had become a world leader in the production of natural gas-based carbon black, selling it as ink under the "Peerless" brand, which won a gold award at the 1900 Paris Exposition.
Binney and Smith even made improvements to carbon black's manufacturing processes via patents like Edwin Binney's 1890 "apparatus for the manufacture of carbon-black." These improvements in the production process, along with the plethora of natural gas discovered during Pennsylvania's oil rush, set the stage for a revolution in the tire industry.
According to an article written in 1992 in the American Society for Testing and Materials' newspaper Standardization News by a Michelin quality guarantee manager, Thomas Hancock — founder of the British rubber industry — and Charles Goodyear — discoverer of the vulcanization process — had patents from the 1830s dealing with adding lampblack to rubber for colouring, but it wasn't until later that tires actually changed colour.
The author, Jeffery A. Melsom, says the true rubber-strengthening benefits of carbon black was discovered by S.C. Mote, a chemist for the Silvertown, England-based India Rubber, Gutta Percha and Telegraph Cable Company, in 1904.
"It wasn't until 1912, however," Melsom wrote, "that this secret ingredient was used in tires by the Diamond Rubber Co. of Akron, Ohio, which acquired the rights to the use of the material from Mote's company."
This is where accounts differ. Melsom says S.C. Mote from Silvertown discovered the value of carbon black in tires, and that Diamond Rubber then got permission from Mote to use the strategy in its tires. But carbon black company Birla gives much of the credit for discovering carbon black's strength to B.F. Goodrich, who owned Diamond Rubber Co, and who was impressed by "Silvertown" tires it had imported from England. Birla writes on its website:
But when [B.F. Goodrich] began experimenting with "Silvertown" tires to change up their look, they discovered that the tread rubber was not just grey — it also had a longer life.
The Silvertown manufacturer had been using a small amount of Binney & Smith carbon black to give its tires their tint, and Goodrich discovered that increasing the amount bound the rubber particles together, making the tires stronger. So in 1911, they put out a request for a manufacturer that could produce an annual supply of one million pounds of carbon black.
Supplying that 450 tonnes of carbon black to BFG was none other than Binney & Smith, who played a major role in uniting a number of smaller carbon black companies into Columbian Carbon Company, which was acquired in 2011 by Birla, the aforementioned modern juggernaut in today's carbon black industry.
So to recap, Binney and Smith, the company that founded crayon-maker Crayola, became a big carbon black producer for inks and pigments, a chemist at a British tire company put the material into tires and possibly determined that carbon black could replace Zinc Oxide (which was used as a reinforcing agent in the early 1900s), then B.F. caught wind of these tires and ended up bringing the technology into the mainstream thanks to a huge order of Carbon Black from Binney and Smith.
So, where does World War I come in? Well, Jack Seavitt from the Ford Piquette plant may have had a point about a munitions shortage, though I think he mixed up magnesium oxide with zinc oxide. I say he might have had a point because I came upon a December, 1988 issue of Fortune Magazine that mentions a munitions shortage:
The market for carbon black exploded after World War I. Until then zinc oxide reinforced the rubber in tires. When the production of brass for shell casings consumed the available zinc, chemists chanced on carbon black, which worked even better.
I also came across this paragraph in Reinforced Plastics magazine:
The date of this discovery is quite ominous as this occurred on the eve of the start of World War I. Zinc oxide had been used as a reinforcing agent in tires, however, zinc is a component of brass and was needed for bullets, munition, and armament components. This set the stage for carbon black to move from a small black pigment business to a global industrial specialty [sic] chemical business. The volume of carbon black supplied to the market sextupled from 1915 to 1924 as a result of this new innovation...
And there's this passage from the book The World Rubber Industry, which discusses why carbon black in tires didn't catch on until well after its benefits were discovered, in part because of weak tire structures being tires' major failure points, not rubber tread:
...tyre carcasses at the time were so weak that improving the tread alone offered little benefit. But then the improvement of tyre carcasses through cord casing, the great upsurge in tyre consumption, and the shortage in the First World War of the zinc oxide previously employed for tyre reinforcement, facilitated increased use of black, and demonstrated its superiority.
Michelin's spokesperson told me the company's first black tires, launched around 1917, were called "Universal Tread Covers," and were advertised as tires built for "all roads and all weathers."
So it's not totally clear how much World War I factored into tires becoming black, as it appears that knowledge of carbon black's strengthening power had existed well prior, as did a vast supply of the microscopic black particles thanks in part to Binney & Smith and the Pennsylvania oil rush.
It seems like a bit of a convergence. At the same time, cars were becoming widespread in the first years of mass production, and tires were becoming strong enough to make long-lasting carbon black reinforcement worthwhile, and other chemical alternatives were restricted during the war.
Still, the fact is that starting just around World War I, carbon black took over from zinc oxide, and tires became black. But more importantly, they became more durable, and still keep that colour to this day.