I'm looking to identify this occurrence but I'm unsure if this is completely on topic here, since this is not my vehicle, and I'm not exactly looking for repairs. I'd just like to find out what caused this, so I apologize is advance if this is out of scope, but curiosity got the best of me and it has been killing me for a while now.

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There is this abandoned car I pass by frequently, in a semi rural area. It has these irregular wiggly lines all over the paint, on the hood, sides, plastic grill, even the windshield.

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They vary in width from a few millimeters up to maybe 2 or 3 centimeters (0.1 ~ 0.8 inches), and on the wider parts have these visible regularly spaced repeating triangular marks.

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At first sight they looked bumpy as if raised above the regular paint surface, like something under the paint puffed up (rust, oxidation?), but as I rubbed my finger over them I noticed they were flush with the surface. The markings also came off easily, revealing no visible "permanent" damage. The surface under these lines seems unspoiled and they are apparently just "dirt" arranged in a strange patterns.

Curiously, despite coming off easily, they are seemingly relatively water resistant, the car has been abandoned for a while, but the marks have been enduring the rainy weather with little fading.

My question is what are these and what causes it?

Things I've ruled out

  • Snail trails: I'd find it strange that snails would scout a surface so thoroughly, I'd expect them to roam more freely. I'd also expect a smooth trail of slime rather than a these erratic dashed lines.
  • Rust : Would probably have raised the paint, and would not happen in the windshield
  • Welding patchwork: Not on the glass or plastics, and would take a lot of questionable craftsmanship for dubious benefit

Side note, I've since seen another (not abandoned, but slightly neglected) car not too far from the illustrated one, with very similar markings.

My search-fu has failed me on this one. Any clues?

1 Answer 1


I'll answer it myself since I've since found the answer after posting.

As first postulated, these are indeed snail marks, against my best judgment.

As revealed by this Family Handy post these are snail lines, but not caused by their body sliding on the surfaces. The tiny triangular marks are apparently made by the snail's mouth, as it repeatedly scrapes off the surface in a line motion within its reach, forming repeated arches as it moves forward.

Snail mouth gif

Snail mouth GIF stolen from Tenor

I assume the wet weather makes delicious edible growth (algae?) thrive on the accumulated dirt, and snails feed on it.

I suppose strictly speaking this isn't exactly on topic after all, since it isn't exactly car specific, but I didn't feel like wasting the post, maybe someone finds this helpful.

Wikipedia image illustrating more snail trails

  • 5
    While I can appreciate the research you did, I will never be able to unsee that GIF. My nightmares thank you =D
    – nitsua60
    Feb 29 at 3:03
  • 1
    @nitsua60 same. Sluuuuurrp.
    – brichins
    Feb 29 at 3:52

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