The Evolution Of Automotive Paint
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Published 2022-06-02
VARNISH
At the dawn of the automotive industry, early motor-vehicles were painted in a manner similar to both wooden furniture and horse-drawn carriages of the time. A varnish-like product was brushed onto the vehicle’s surfaces and subsequently sanded and smoothed. After multiple layers of varnish were established, the vehicle was then polished. Varnishes are generally composed of a combination of a drying oil, a resin, and a solvent.
LACQUERS
The first true automotive specific coatings would emerge in the early 1920s as a result of an accidental discovery. This liquid became the basis for nitrocellulose lacquer, a product that would become a popular staple of the automotive finishing industry for decades to come. Nitrocellulose was the first man-made plastic and it was created in 1862 by Alexander Parkes.
Dupont chemist, Edmund Flaherty, would go on to refined the use of nitrocellulose dissolved in a solvent, to create a system that used a combination of naphtha, xylene, toluene, acetone, various ketones, and plasticizing materials that enhance durability and flexibility, to create a fast drying liquid that could be sprayed. Nitrocellulose lacquer has the advantage of being extremely fast drying, and it produces a tougher and more scratch resistant finish.
ENAMELS
By the 1930s, the development of alkyd enamel coatings would offer a significant enhancement over the properties of existing lacquers. This reaction occurs between the fatty-acids of the oil-portion of the resin and oxygen from the surrounding air, creating a durable film as the solvent evaporates.
ACRYLICS
In the 1950s, a new acrylic binder technology would be introduced that would transform the automotive coatings industry. Acrylic paints are based on polyacrylate resins. These synthetic resins are produced by the polymerization of acrylic esters or acrylates, forming a durable plastic film. Like previous systems, the acrylates are dissolved within a hydrocarbon solvent and applied using spraying.
However, unlike alkyd, acrylate polymerization occurs without surrounding oxygen, and in most production acrylic systems, is initiated with a catalyst based on isocyanates or melamines. Polyacrylate resins do not easily absorb radiation in the solar spectrum, giving them excellent resistance to UV degradation, when compared to previous resins.
UNDERCOATS
Since the inception of its use, most of these undercoats or primers were composed of a combination of alkyd and oleaginous resins to produce an interface coating. Initially these coatings were applied to individual panels through dip coating, though this would eventually evolve to a combination of dipping and spraying entire body assemblies. Because undercoats directly interface to the vehicle's base metal, they serve as the primary form of corrosion protection.
However, the process by which they were applied resulted in inconsistent coverage throughout the vehicles. This was due to recesses and enclosed areas on the vehicle’s body. In the 1960s, Ford Motor Company would pioneer a dramatically different approach to vehicle priming through electrodeposition. The car body is coated on the production line by immersing the body in a tank containing the aqueous primer dispersion and subjecting it to a direct current charge.
EPA
By the end of the 1970s, the EPA had sought to reduce photochemically reactive hydrocarbon solvent discharges from industrial finish operations by introducing emission requirements that restricted finishes to be sprayed at a minimum volume solids content of 60%.
CLEAR COAT
This initiative led to a new approach to how automotive finishes were utilized, with specific functions of an automotive coating now being directly engineered into each layer. In the Late 1970s, the first wet-on-wet systems were developed that consisted of a thin base coat and a thicker clear coat. This separation of coating function now allowed for completely different chemistries to be employed between layers. Based on solvents composed of glycol ethers and water, these systems dramatically reduced hydrocarbon emissions and were generally high solid in nature, easily meeting EPA requirements .
POLYURETHANES
Modern automotive coatings overcome these limitations by using a hybrid dispersion of acrylics, polyurethane and even polyesters. These systems, known as acrylic-polyurethane enamels, incorporate the monomers of each resin in a proprietary combination that, once initiated by a catalyst, undergo polymerization. By adjusting the constituent resins and their quantities as well as the catalyst formulation, the sequence and rate of how this polymer network is formed can be modified, and the properties of the composite film adjusted to suit the needs of the product.
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All Comments (21)
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i have worked on cars for some 50 years and now have a collection of old "mopar" muscle cars. after graduating from high school in 1972, i built and ran an auto body shop for three years and then went on to college and law school. i was the main "paint guy" at my body shop. in the 60's and 70's, GM used Acrylic Lacquer and Ford and Chrysler used Acrylic Enamel paint. both these paints were "single step" paints meaning that you just shook the paint vigorously, thinned it (usually 2-1) with a Lacquer or Enamel thinner, and then sprayed the paint on the vehicle. most colors required at least two coats - except black. the "metallic" paints (paint with small metal flecks) had to be applied in a certain way or you would get what was called "tiger stripes" meaning that you could see broad "mismatched" areas where the metal fleck "laydown" was mismatched from one area to another. the thinners for these paints came in three temperatures ranges, fast drying, medium drying, and slow drying. you used fast for cold shop temps and slow for hot shop temps. Lacquer was the easiest to use as if you made any mistakes like a dry spot, a "run in the paint", or the pesky fly that hit a panel, you could wait an hour and the paint was dry and hard enough to sand down and completely refinish. Acrylic Enamel was a different story. that paint was a little thicker in viscosity (as it had more clear acrylic in it) and you usually had to wait 24 or even 48 hours to sand and refinish Enamel. it was also easy to "blend in" small repairs or "partial panel painting" with these paints. there was little difference in appearance between these two paints, however, a skilled bodyman or painter could tell the difference between Lacquer and Enamel vehicle paint. i closed my body shop in 1974 to go to college. when i retired from my law practice in 2016, i started my car collection. i have found that the "water based paints" are AWFUL and CANNOT be used by a private person in their house garage. you MUST have a professional, commercial "paint booth" to spray the water based paints as they need constant air flow and "heat" to cure properly. the "base coat, clear coat" paints can be sprayed by a "do it yourself" private car restorer. i restored and painted one of my 1968 Plymouth Barracuda's using Acrylic Lacquer that I was able to get "custom mixed" and painted that car in the garage of my house. it came out very nice and looks just like the paint that would have been on the car when it was new in 1968. one thing about painting "old cars" - if you are a "purist" and want your car to "look like it did when it was new", you have to find a shop that can spray the old single step Lacquer or Enamel. ALL the new paints, water, base-coat/clear-coat, "Emron" type paint using an additive or "hardening agent" - all those paints have a MUCH higher gloss than paints had 55 years ago. only a few "luxury" cars "back then" had REALLY glossy paint jobs - like the Cadillac's and Lincoln Continental's. there were no Chevy's or Fords or Plymouths or Dodges or Pontiacs or Buicks or Oldsmobile's that looked like the cars do today. like so many things in this world now, EVERYTHING is much more complicated - AND EXPENSIVE!! when i contacted PPG (a major car paint company) to get a gallon of Acrylic Enamel to paint my 68 Barracuda with original paint (yes, PPG still manufactures some old OEM paint products), they said, "Yes, we have that paint, it is $1000 a gallon." i ended up painting the Barracuda with "Lacquer" at $327.00 a gallon. it is not unusual for a simple, modern repaint of a car costing $10,000 today. when i ran my body shop in 1973, we charged on average, $150.00 for a complete repaint. there was a guy named "Earl Schieb" who had a series of "franchised" body shops around the country who advertised "A new paint job for $29.99!"
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Really enjoy your videos dude. You choose unique topics and research them on master level. The footage you use is the best part- I dont know where you find all the clips. Then you deliver the fruits of your research in the way a true master of that topic would - easy to follow with a great structure that keeps focus. Truely well done, so few gets this right. Lastly- I've started to notice big channels on youtube copies topics off one another, many of them, not you sir- your topics are fresh!
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Awesome. IMO this represents the best species of educational YouTube video: something completely quotidian, viewed through a completely unexpected perspective that elevates it to another level of interest. I would never have viewed paint as a form of technology, but it totally is!
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As an automobile historian, I really appreciated this video: well researched and tackling an often overlooked topic. Well done 👍
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Great video… I have a suggestion for a part 2 companion video. You could cover the color pigment process… the search for rare materials, why some colors take years to perfect and why said colors are expensive up-charges. It’s an aspect of the industry that flys under the radar.
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As a COF.....Certified Old Farte.....I remember when GM used lacquer, Ford used enamel, and all red pigments faded faster than light at sunset. Late 80's I had a roommate that was a master painter and then went on to be a salesman for an auto paint company. We had many a conversation about paints, myself having done some basic painting. With the base coat urethane topcoat system, we've hit auto paint Nirvana.
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Never thought I'd be interested in something like this, yet here I am. Watching the history of automotive paint
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At 11:30. As far as I'm aware wet-on-wet doesn't usually refer to clear over base. It refers to spraying base over a smoothly applied primer or sealer that is not sanded or fully cured. It can save time but obviously the underlying surface needs to be well prepared and perfectly flat in advance. Technically the application of the clear over the base coat is the same technique but that terminology isn't used because that's the only way to do it.
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Simply put, This is the best video on Automotive coatings, that exists on YouTube. Kudos on a stellar production !!!!
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Been painting cars for 8 years.. what a cool video! I have sprayed both modern water based and solvent based paints. In my experience water paints provide a better user experience, but solvent paints generally provide a more durable product that can be more reliable and less finicky in the long run. With a good painter using the correct products, it can outshine waterborne as well. I spray a hybrid of the Axalta Cromax system.. Standox base coat which is ok, but with their 7900s series clear coat, it is absolutely phenomenal. The clear really makes the product.
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Detroit Agate, Motor City Agate, or Fordite, is a type of “stone” made from automotive paint that accumulated on factory equipment over the years. It has many layers/bands of wildly-varied color. People sometimes shape it into jewelry.
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Somebody show this to Mazda and Alfa. Especially the "rust-preventing-layer" bit.
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Regardless of your views on the environmental impact of modern industries, you have to give props to the engineers and scientists for solving so many problems with so many constraints.
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acrylic laquer and polyurethane will always be the best coating that I worked with acrylic laquer for custom painting and polyurethane for bependablety Great video I did a lot of painting in the early '70's and '80's lot's of artwork with acrylic laquer...and even with Imron polyurethane's I seen some cars and vans painted 10+ years ago and they looked like they were done yesterday that paint could take a lot of stones bouncing off them and still look like new . .
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I had a thought about how remarkable automotive paint was just a day or so ago on a drive, what a happy coincidence this is! Excellent video as always.
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I know I say what others already said, but damn man, your content is so rich in information and details as well as very easy to digest [English isn't my native language and I have zero problems following the script]! I am so thankful that you put out these videos, each one is a little gem that shines brightly throughout the platform. The topics that you choose aren't even what I would look for, but I am being sucked into the topic, whatever it may be, and I find it VERY interesting after you explain it. Thank you!
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Very interesting. So much engineering goes into things that seem so simple.
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What a great video! As a coating and corrosion engineer the history was fascinating.
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This is the best presentation of automotive coating concepts that I have seen. Good work.
