Watching Paint Dry: The unexpectedly interesting story of car coatings

https://edconway.substack.com/p/watching-paint-dry

by rwmj • 3 years ago

175 99 3 years ago

edconway.substack.com

linksnapzz4• 3 years ago

The paint shop at a modern car assembly plant can be 50% of the square footage under the roof, and cost 50% of the outlay, so half a billion for a new one at least.

The change from VOC-borne to water-based paints was also a big deal for the environment. The lacquers did a good job, but imagine living in a neighborhood where several tons of toluene or acetone was being evaporated into your air every hour. In places like LA, this process was a huge contributor to smog in the 1960s/70s.

csours12• 3 years ago

I used to work in an automotive paint shop. When our exhaust scrubber (burner) went down, we had to stop painting cars. We had a 'budget' of VOC exhaust per year. I don't know when that went in, I imagine in the 80's or 90's.

We switched to water based paints in 2013 and that really helped with the VOC.

dghughes• 3 years ago

Take care of yourself!

My neighbour was a car painter for decades he died of dementia. My Dad and grandfather had a house painting business in the 1960s/1970s using leaded paint for most of that time. Both Dad and my grandfather died of lung diseases.

sokoloff3• 3 years ago

On the other hand, at least the early water-base painted cars were prone to premature rusting, which has its own (distributed) ecological impact. My W210 Mercedes was mechanically great the day I sent it to the scrapper for excessive rust through on the rockers and underbody structure. Hundreds of thousands of car met such an earlier than otherwise demise.

linksnapzz4• 3 years ago

Glad you liked yours; the 210s and 220s and the original MLs were the nadir of Mercedes value-engineering when it came to many things, and rustproofing was certainly one of them.

geepytee2• 3 years ago

You should tour any of the Tesla factories, this is not the case.

linksnapzz4• 3 years ago

I'm pretty sure the cost is still a large part of the plant budget, as well as the floorplan.

Also, Tesla isn't all automakers.

danzk4• 3 years ago

Acetone is not considered to be a VOC.

https://en.wikipedia.org/wiki/VOC_exempt_solvent

daniel_reetz• 3 years ago

Interesting. It's still difficult to purchase in CA. Used to be sold at Home Depot, now it's "Acetone replacement". I have to go to specialty suppliers.

DannyBee3• 3 years ago

Acetone is not a VOC. Also, Don't confuse VOC, which is about air pollution, with toxicity, which is not. Toluene is a very slow evaporating VOC that is toxic. Not all VOC are toxic and not all toxic solvents used in coatings are VOCs.

Most 2k water based urethanes with isocyanate hardeners are ~zero VOC (and colorless + odorless at less than harmful concentrations) but much more toxic to those spraying and within inhalation range. Thankfully we are moving to iso free formulations.

It happens that the isocyanate reacts with moisture in air fast enough that it won't harm many others but again, VOC != Toxicity.

I would rather have non toxic air pollution than colorless odorless toxic gas, and there are plenty of examples of VOC regulation generating the second.

It's one of the fun lies that paint companies sell (0 voc = safer for you. Non VOC is good for environment in general but tells you nothing about safety)

meepmorp• 3 years ago

Acetone is not a VOC.

Acetone is absolutely a volatile organic compound (VOC). It might not be toxic, but it's an organic solvent with a high vapor pressure at relatively low temperatures.

AlbertCory• 3 years ago

There are actually videos on YouTube of watching paint dry, e.g.

https://www.youtube.com/watch?v=PLOPygVcaVE

1.3M views! I found the plot a little thin (drum roll).

aidenn0• 3 years ago

I think you meant rim-shot, not drum roll?

david422• 3 years ago

Gonna watch that on 1.5x speed.

doctorhandshake• 3 years ago

Might be a little OT but I was hoping this would include more discussion of the contemporary interplay between aesthetics and paint chemistry / technology.

I know there are some interesting stories behind titanium dioxide production, the use of which is critical to making paints vibrant and opaque [1].

Further I have a pet theory that the recent trend in 'flat' automotive paints (without the apparent depth and larger suspended metallic flakes common in decades prior) has been enabled by some kind of technical advance as well, not just a change in consumer tastes, although I have no evidence to support the idea [2]

[1] https://www.theverge.com/2014/3/6/5476904/china-stole-the-co... [2] https://www.latimes.com/business/story/2023-03-07/la-fi-car-...

notjulianjaynes• 3 years ago

Further I have a pet theory that the recent trend in 'flat' automotive paints (without the apparent depth and larger suspended metallic flakes common in decades prior) has been enabled by some kind of technical advance as well, not just a change in consumer tastes, although I have no evidence to support the idea.

I've wondered about this as well. One theory I've had is that older paints used lead based pigments which gave a glossier finish, but are no longer used. I also do not have any concrete evidence to support this aside from pointing out that automotive paint was exempted from the 1978 (US) lead paint ban.

eig• 3 years ago

For those of us who would like a little more depth in the history and chemistry of automotive paints (and more images/videos too), there's a great video essay by New Mind on youtube:

https://www.youtube.com/watch?v=b_hgPinCZks

I was quite surprised at how important paint actually was to car production.

wlesieutre7• 3 years ago

That's a lot of work to paint 80% of new cars in the most boring colors possible

crazygringo5• 3 years ago

Then what's boring to you is clearly tasteful to the 80% of people buying them.

I personally like to express my personality in other ways. The last thing I want is a car screaming some garish hue. Especially since I can do things like match clothes to my mood and the season, but I can't get my car repainted every day or every three months.

mhb2• 3 years ago

The gap between boring and garish is at least big enough to drive a Mini Cooper through.

Swizec• 3 years ago

Then what's boring to you is clearly tasteful to the 80% of people buying them.

Apparently this has to do with how the economy is doing. When times are tough, people like boring car colors. Something about ease of resale and broad palatability in car dealerships.

https://www.cnbc.com/2020/09/22/most-cars-are-painted-one-of...

wlesieutre7• 3 years ago

It's not even really up to customers today, most people (me included) will take whatever color is available as long as it's not hideous. That's how I'm ending up with a white car even though I'm not enthusiastic about it. I guess manufacturers know that, so it's no problem for them to keep cranking out the whites and grays.

Was talking to a Mazda salesperson recently and he was complaining that the first five or six of the new CX-90s they were being allocated are all white. Though looking at their website they have some red and dark blue ones on the way now, so maybe that was just the first production run.

seabird• 3 years ago

Not every car that isn't black/white/gray is garish, and at least in the US, most people have unbelievably bad taste when it comes to vehicles.

nicenewtemp84• 3 years ago

I worked in car sales for a decade.

If you like model xyz, and you like red, but we only have it in Silver, you'll probably buy it.

If you like model xyz, and dislike vibrant colors (very common), you won't buy the red one we have.

wlesieutre7• 3 years ago

It's true, if I weren't married I'd be getting Soul Red Crystal. Gorgeous color. But it's not for everyone, apparently.

And the blue option isn't available, so white is it. If they had literally any non-red color we would've bought it, but they didn't.

sp332• 3 years ago

They just stopped putting flake in the paint. https://www.latimes.com/business/story/2023-03-07/la-fi-car-... & https://news.ycombinator.com/item?id=33880005

DannyBee3• 3 years ago

You can get whatever color you want in most luxury cars, you just have to pay and wait for it.

Audi will happily get you a Lamborghini yellow q5 if you want.

1970-01-01• 3 years ago

They all use electrodeposition and most of them use robots to do most of the car spraying. They are gradually beginning to explore replacing their gas ovens with electric ones to reduce the carbon emissions at plants.

Toyota's electrodeposition and prep process can be seen here:

https://youtu.be/DLav5xRvWUo?t=269

hedgehog• 3 years ago

Pretty cool. For the next step the sprayers don't work like a normal spray gun, instead of pressure they use a spinning contraption to mist the paint and static electricity as a kind of terminal guidance to get over 90% of the paint onto the object being painted.

https://en.wikipedia.org/wiki/Rotational_bell_painting

https://www.youtube.com/watch?v=JuvFX-Y5tyk

csours12• 3 years ago

I used to work in an automotive paint shop. Another point of interest:

There's a limit on the number of tries you have to "repair" the paint job, because the vehicle has to go through the oven again to bake the coatings. The trips through the oven affect more than just the paint. Some panels are filled with foam; there's internal sealant and glue, and external sealant. All of those things don't really love being baked too long. For the shop I worked in, we got 2 tries to repair.

The main limit on repairs though? The windshield. Windshields are glued in with specialized urethane 'caulking'. They have to stick to the paint, and the paint has to stick to the body. That is only certified reliable with less than 5 trips through the ovens (in my shop).

---

Paint is the hardest thing to get right in the whole assembly process, because there are so many process variables. Temperature and humidity (dew point) are the biggest besides the actual paint mix, but there's also unexpected problems from every direction. Our solvent paint process (pre-2013) was very vulnerable to siloxane (silicone) lubricants. Someone in IT applied some lubricant to a label printer and ruined hundreds of paint jobs. Livestrong bracelets also ruined at least a hundred paint jobs. Someone did weekend work on the roof? Congratulations on your dust quality spill (spill means a bunch of problems).

All of the parts of the paint have to work together, and that includes things that you don't think are paint. The body is just dumb metal, right? Of course not. The metal panels have oil on them in stamping, and they MUST stay oiled right up to the point where the body takes it's first bath. If too much of the oil has evaporated, then you start getting corrosion, and in many cases you won't be able to tell until the vehicle gets to the customer.

---

Paint shops have the most complicating routing of any part of automotive assembly. The electronic quality and build data has to be synchronized with the physical process, and that data package can be updated by several different systems. Then either IT or OT (operational technology) can make a routing decision, or an individual can use a key switch to manually change routing. "Why did this vehicle go here" is not a straightforward question to answer sometimes.

EvanAnderson3• 3 years ago

Thank you for this comment. I enjoy hearing about intricacies of engineering processes-- particularly those that sound "easy" on the surface.

This gives me a deeper appreciation for cars with plastic body panels. I also wonder if DeLorean Motor Company took any of this into account when they designed the DMC-12 with stainless steel body panels.

csours12• 3 years ago

Plastic panels are a whole bucket of issues in themselves. As far as I know, the color matching plastic panels are painted using a different process. That means the the front and rear fascia (bumper) of your vehicle are painted in a different plant (usually) from the rest of the vehicle. The colors have to match to a very high degree.

And yes, that's a big reason why they went with stainless. Stainless steel does corrode, just much less visibly than regular steel. It also has different physical properties like work hardening etc. It's also VERY expensive. Salty napkin math says $10,000 more for the Cybertruck.

buildsjets• 3 years ago

The DMC-12 had stainless steel body panels, but it had a plain ol' carbon steel frame (designed by Lotus and similar in design to the Esprit) with an epoxy coating, and they have NOT fared well over the years. You can buy a new-build stainless frame for it, it only costs as much as a new regular car.

https://deloreanindustries.com/8-1-0-stainless-frame/

crazygringo5• 3 years ago

This is fascinating, thanks. Can you elaborate more on how the label printer and Livestrong bracelets ruined paint jobs? Was it something they emitted through the air? How would that be in concentrations to affect the paint job, what would happen to the paint?

csours12• 3 years ago

Silicone oils caused the paint to "run away", like putting soap in a greasy pot.

Droplets were enough to cause problems - there's no hiding problems on a car's paint job and customers are VERY demanding.

danzk4• 3 years ago

Silicone has very low surface tension, imagine water on a non stick pan. If paint encounters a droplet of silicone it will shrink back on itself and form a hole around the contamination.

bluGill3• 3 years ago

The metal panels have oil on them in stamping, and they MUST stay oiled right up to the point where the body takes it's first bath.

I toured an assembly line a few years ago. The guide told us that in the 1970s they had teams of people watching iron/steel prices, when they thought the prices where at the low they made a massive order of all iron that factory would need for the next few years. When the factory when to just-in-time (sometime in the 1980s or 1990s) they couldn't do that anymore - but they also got to get rid of all the equipment to de-rust all that stored iron: since every raw material was shipped out as a final assembly in a week there was no time for significant rust to form and so they avoided a lot of problems.

csours12• 3 years ago

JIT assembly has SO many non-obvious implications. I had not heard of this one, thanks.

refurb2• 3 years ago

Any reason why an automobile manufacturer couldn't buy a steel futures contract to fix the price?

geepytee2• 3 years ago

You were painting bodies with windshields already bonded onto them? Seems like a good idea to adhere windshields after paint.

singleshot_• 3 years ago

I got the feeling they were in an auto body shop, where the paint might be trashed and the windows might be fine.

csours12• 3 years ago

Nope, the windshields go on top of the paint, but the requirements for the windshield affect the paint process.

akiselev2• 3 years ago

That sounds fascinating and complicated. I scratched my car a few years ago and decided I wanted to DIY a chameleon paint job instead of taking it to the shop (the car is worth less than the paint job if I pay retail). I’ve been slowly acquiring all the gear I need like a forced air respirator and sprayers.

I was wondering how realistic that really is to DIY or if I’m kidding myself. Sound like even if I rented a stall in a paint shop for a few weeks, I won’t have the time to finesse the technique to get a good end product, especially with how much more finicky I understand the chameleon paint to be.

csours12• 3 years ago

My understanding about chameleon paint is that it's very hard to match if it's not all painted at once. I think the difficulty may depend on your expectations for the final product.

jasonwatkinspdx• 3 years ago

Maybe vinyl wrap would be a more approachable solution? https://www.rvinyl.com/Chameleon-Shade-Shifter-Vinyl-Wraps

dekhn• 3 years ago

these innovations spread back into the normal paint world, I've come across a number of things about modern paint that show it was first developed for cars (and mostly GM/Ford). Automobile primer is great for covering 3d prints.

ZeroGravitas• 3 years ago

Masking tape being a notable example:

By the early 1920s, two-toned cars were the rage, and that created a major headache for the automotive industry. To craft this duo-tone look, one portion of the car had to be masked off while the other was painted. The problem was nobody knew how to do this well. So automakers and auto body shops improvised. They glued old newspapers to the body and windows with library pastes, homemade glues or surgical adhesive tape. This helped create a sharp demarcation between the two colors, but the adhesives stuck so firmly that trying to remove them often ruined the paint job.
At the time, 3M primarily manufactured sandpaper and other abrasives. One of Dick Drew's jobs was taking samples of waterproof sandpaper (another 3M invention) to nearby auto body shops for testing. One morning in 1923 he walked into one of these shops and overheard "choicest profanity I'd ever known." Yet another paint job was botched and the worker who'd done it was furious. Drew had seen this occur on many other visits, but this time he spoke up. He could, he said, produce a tape that would end the painter's torment.

legitster• 3 years ago

There's so much more detail you can go into in this stuff.

Before the Model T assembly line in 1916, most manufacturers did something like 6 or 7 coats by hand because it was such thin, slow drying varnish. And to get that nice shiny enamel surface we are used to with hand brushes, they had to alternate the direction of the brushstrokes between every coat as well as sand it. In addition to time, this is a huge QC issue.

Part of the magic of the all-black Model T is that you can just dip parts that can be dipped, Japan parts that can be Japanned, and pour paint on parts that cannot. At final assembly they will all be matched up together without any mismatching paint jobs.

And we cannot understate how magical the introduction of asphaltum and naptha were to the paints. This was still pretty new technology then and the precursor to our modern petrochemical derived paints and even plastics. You could get thicker coats that dried faster. So paint could just be poured on and the surface tension would smooth the surface perfectly. And they were more durable because they produced a more flexible coat.

One of the innovations of the Dodge Brothers (that Ford later copied) was that by using more metal body components, not only do you save on labor (working with wood is much more skilled than running a metal press) but that metal can withstand the much faster oven-baked finishes.

ughitsaaron• 3 years ago

The conventional wisdom is that Ford decreed that all Model Ts should be black because that was the fastest-drying of all colours

Is that actually the conventional wisdom?

danzk4• 3 years ago

I believe it's a myth. It was most likely due to efficiency and cost reasons. Black was cheaper than other pigments and was less likely to show imperfections.

mhb2• 3 years ago

These days, where we use enormous ovens to cure and dry car coatings, it is comfortably the most energy intensive and carbon intensive parts of making a car.

I guess so if you don't count what it takes to make aluminum and steel.

yread• 3 years ago

a friend (a paint engineer) believes there are massive energy savings to be had from the painting (baking). He was shocked to see how wasteful the process is in automotive plants compared to his other clients. All because the paint has to be perfect and last long

csours12• 3 years ago

It would be better phrased as "most ... intensive part of an automotive assembly plant". Generally, the only big thing that assembly plants actually manufacture is the body (including painting the body)

Once production was shut down at my plant because it was too cold and the natural gas company said they had to use the gas for residential customers.

tomcam3• 3 years ago

As an old-timer, I can tell you that modern automotive paint is off the charts gorgeous end of a quality that would have looked like alien technology in the 1970s. One color you will see frequently is a metallic red that consists of the red pigment with fine metal particles that give it a deep glimmer. 30 years ago the only way you could get that was a very expensive coding process that required 10, 12, 20 layers of paint. Now anyone can get it on their Corolla for little or no markup.

Another piece of trivia is that Fender, the guitar company, has often used automotive paints for its guitars. The reason is not just availability and durability, but that it accurately tracks recent color trends.

greenthrow2• 3 years ago

Fender only followed car color trends in the late 50s and early 60s. After that they went their own way (including natural wood bodies and many "interesting" color choices of the 70s.)

Most Fender guitars sold today are still in those "custom" Duco colors from the late 50s and early 60s. (The standard Stratocaster was a burst color and the standard Telecaster was butterscotch or blonde. Any of the Duco car colors back then was a "custom" option for an additional charge.)

tomcam3• 3 years ago

I interviewed their #2 guy for a radio show a few years ago and he's the one who gave me that info. In fact, they follow lots of other color trends--right up to and including women's shoes (not joking). I called him out on it and he said, "Do you have any better ideas?" and that shut me up really fast.

csours12• 3 years ago

There's a red tintcoat that's just amazing. It's red basecoat with a red tinted clearcoat. So much depth, I feel like I could wade through it.

supportengineer• 3 years ago

The red paint on recent Mazdas specifically - I stop and stare every time.

tomcam3• 3 years ago

YES

danzk4• 3 years ago

Mazda Soul Red is what's called a "Candy Color“. It's achieved with a translucent red layer applied over a base color layer. It's rare for an OEM to offer a color like this because the thickness the coating is applied changes the color and It's much more difficult to achieve a consistent color.

emmelaich• 3 years ago

These days people using vinyl wrap as well.

e.g. if you see a Tesla in other than white, red or blue, then it's probably:

https://www.3m.com.au/3M/en_AU/p/c/films-sheeting/vehicle-wr...

intrasight• 3 years ago

Great article. Reminded me of this article about the mineral "Fordite" that I recently read:

https://www.boredpanda.com/car-paint-deposits-fordite-detroi...

Many dozens or perhaps hundreds of "watching paint dry" cycles results in some spectacular agate-like specimens.

Gupie• 3 years ago

Strange seeing "duco premier email a froid" in the vintage poster! I assume it is vintage? Anyone know what "email" means in this context?

ShakataGaNai• 3 years ago

https://www.1stdibs.com/furniture/wall-decorations/posters/o...

" Cellemail le premier email a froid Francais / Cellemail the best French cold enamel "

So, I think it's french for enamel? Based on that link.

glandium• 3 years ago

Yes, émail is French for enamel.

photochemsyn• 3 years ago

Great article, I agree that "the influence of the chemical industry on modern products is astoundingly important, yet it’s one of the least appreciated and most rarely told stories in the modern industrial pantheon."

BXLE_1-1-BitIs1• 3 years ago

In the mid seventies I painted my newly built harpsichord in three colors with alkyd paint. Six coats with sanding between. It took about a month. After the final coats, it took several grades of wet sanding followed by rubbing compound.

Then there's composite gliders. Gelcoat is sprayed into molds before layers of fiberglass, Kevlar, or carbon fiber alternated with adhesive is laid into the mold.

Gelcoat durability is problematic. Eventually you have to sand WITHOUT damaging base layers before repainting.

Composite adhesives can be toxic. I know a canoe builder and a glider repair engineer who died prematurely – and two harpsichord builders.

Watching Paint Dry: The unexpectedly interesting story of car coatings

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