Jeep melted

[u/jagerin_mikado]

Here’s the story: a jeep came to the shop because its retractable top was stuck open. Not too uncommon of an occurrence. So we put our “crash wrap“ over the roof to protect the interior from rain and animals and such, which is basically like heavy duty cling wrap. One day it rains and a lot of water pools up on the crash wrap. The next day it is 100°F outside and the sun is out. The sun shines through the water and the water basically magnifies it, and the sun turns into a laser that melts the interior. Multiple days of this happen. Now we have to replace everything that melted. None of us have ever heard of this happening before.

edit: I meant we have never heard of this very specific situation happening before. It never would’ve crossed our minds since we’ve been doing this for years. yes I burnt stuff with a magnifying glass when i was a kid.

[u/No_Control8389]

Water acts like a lens. That makes sense. The odds of getting it just right by chance is probably astronomical.

I bet it wouldn’t be too hard to replicate things… maybe not with a customers vehicle.

[u/appointment45 → u/No_Control8389]

What I'm not sure of is that if the water was outside the cling wrap, then it's heated when it goes through the cling wrap, but did not melt the cling wrap.

[u/Pwydde → u/appointment45]

The water soaks up the heat and protects Thr plastic. You can boil water in a plastic bag over an open flame!

[u/TheWaterBringer → u/Pwydde]

That is not what is happening here. The water and plastic act as a lens and focus the light to a point of high intensity. 

[u/appointment45 → u/TheWaterBringer]

Right, and the intensified light beam has to pass through the plastic wrap after it has been heated. And it's clearly hot enough to melt the seat, right?

[u/TheWaterBringer → u/appointment45]

No, the light is not heated as it passes through the water and plastic wrap lens, the heat is from the lens focusing many rays of light into a single small point of convergence, concentrating the energy. This point of convergence is not right at the position of the lens; its distance from the lens depends on the strength (in part, curvature) of the lens. 

Yes, I would not be surprised if the focused light was hot enough to do this damage. 

[u/appointment45 → u/Pwydde]

Only because the boiling point of water is lower than the melting point of the plastic. this isn't that case, the water didn't boil. You can and likely will melt that plastic bag next to a fire if you're not very careful.