I was thinking about swirl marks...

C

Corey Bit Spank

Active member
And the causes. And while I do know...KNOW...that dirt and grime and poor washing and drying can create them, the inevitable swirl marks happen on the best kept cars.



So, it's making me wonder, do swirl marks occur more due to the enviroment? Changes in hot and cold (seasonal, night/daytime, a hot car that gets washed, dried, and then the paint heated up again under the sun).



Swirl marks just seem to be too uniform to all be created by human.



I apologize if this is a repost :(
 
Something else to add. If swirls marks are cause by improper washing and drying, why are they always circular in nature, even though I wipe back and forth?
 
John Styrnol said:
Something else to add. If swirls marks are cause by improper washing and drying, why are they always circular in nature, even though I wipe back and forth?
Click to expand...



I was going to post a thread today on this exact same question.
 
Very interesting questions, i have wondered the same, i use the back and forth method w/ everything that i apply and yet i sometimes get light swirling in someplaces. I also had a thought while driving recently, do leaves cause light scratches that can lead to swirlmarks, i was driving through a tree lined raod and leaved were falling on my car, it upset me, and then i thought about the swirls and how if u even drive ur car its more than likely swirls are happening by things out of our control, then i thought, what does brake dust do? Would the blowing of brake dust by the wind grind against the paint causing very microscopic marring of the paint?Oh, so much to worry about.
 
From what I can tell, and I'm talking about close inspection of paint surfaces with a microscope and other detailed imaging equipment, the "swirl" effect seems to be caused by all types of scratches.



In almost all cases I could see a cross hatch lattice of micro scratches, sometimes with a bias in one direction, i.e. in the direction most people wipe the paint when washing.



It took a little research in the effect of light reflection to figure out why we see circular marks instead of the cross hatch I could see under the microscope. It sort or works like this. The light is coming from a single point source, and it enhances the look of scratches that are perpendicular to the direction of the light. This means that we can see only the scratches perpendicular to the single point light source, and only the section of the scratch that is perpendicular. Which adds up to many straight scratches been highlighted just in the area that is perpendicular, which together look like a circular swirl mark.



The density of these scratches will effect the density of the swirl marks we can see.



I'll do a couple of pictures up to demonstrate as I think my explanation is a little fussy.



Greg
 
Here's a couple of images to help explain what I mean.





A rough representation of many straight scratches.

Magnified-Scratches.jpg




And now with the light source added (background colour changed to make it easier) and the areas highlighted are the parts of the scratches that would now be visible to the naked eye.

Magnified-Scratches-Highlighted-Black.jpg




Obviously I have only been able to put in a limited number of lines to represent the scratches and in real life there would be many more in many different orientations, which make the swirl look more rounded than my images. As I said before it's only a rough representation but I hope this helps with the explanation.



Greg.
 
I always figured they were caused by dust/dirt/particulates essentially eroding the finish on the car when driving. I also figured that the vortices that form on the cars surface when driving it were why they were swirly. Just a theory...
 
I dunno about the swirls being inevitable...I kept the S8 *totally* marring free for over two years, and that's driving it year-round. The only time it *ever* got any marring was after/during the "deer incident" repairs. But it took incredibly diligent/meticulous wash/dry/etc. regimens to keep it that way and I couldn't have done it without a spotlessly clean garage either. It's just a lot easier to mar paint than most people can ever imagine or should I say, a lot harder to avoid it...



I've seen plenty of cars with perfectly straight marring, or at least it was straight when I looked at it under controlled conditions. I'd say EclipseDetail has the right idea about why the marring often appears circular even on cars that don't get circular motions used on them. But most of the time, people do use circular motions.
 
I wonder how we get what looks like millions of pin holes or pores on older paint. Is it from the water beading and acting like thousands of magnifying glasses putting minute holes in our paint or just from being sand blasted going down the road or something in thew environment eating away at our paint. Do you know what I am talking about, it can usually be seen real good on black.
 
Just to expand on EclipseDetail's explanation...



The more your light source throws light in multiple directions, the more you'll see the circular swirling. The micro grooves are there.. what you see just depends on the light source.



Most incandescent lights (i.e. halogens, regualr light bulbs) throw light in all directions. Therefore, you will have many grooves at all angles being perpendicular to the light being thrown so will see many of them. Also, the greater the intensity of the light source, the greater the reflection and therefore the better the grooves show up. That's why high wattage halogens are great for spotting flaws in your work and driving you mad...



Contrast that with LED light sources which throw light in a relatively narrow, focused manner. Try shining one of those LED flashlights on your paint and you'll see very little.



The reason you see so much less swirling on silver/gold cars is because whatever light is reflected off the grooves edges is overwhelmed by the light reflected from the silver paint and back through the clear. Black, on the other hand, absorbs the light so very little light is reflected back through the clear.
 
agentf: I see those frequently, yes, on older cars, including my 92 black Miata! If you get it figured out, be sure to let me know. It *almost* looks sandblasted . My paint is sooo thin, i don't dare go after them...



But it is Shiney, nonetheless!



Jim
 
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