Busted By Science: Those Videos Of Comically Inflated Vinyl Wraps Are Not What You Think

It’s hot in China right now. It’s summer, after all, so that’s to be expected. This year, though, the heat has spawned a viral video showing “pregnant cars” with huge round bubbles on their hoods and doors.

The implication is that a Chinese heatwave has been so extreme that it caused vinyl wraps to balloon up to this immense degree. There’s a certain intuitive nature to this. Heat makes things expand, air included. Thus, extreme temperatures could make vinyl wraps balloon out like a big pregnant belly, right?

Many outlets fell for this, including The Times of India and The Express Tribune. But a casual examination suggests the whole heatwave explanation is pretty nonsense. Let’s watch the video, do a little science, and talk about what’s really going on here.

Protective films on vehicles inflated in heat wave in China
pic.twitter.com/jcCu3v9gk1

— Science girl (@gunsnrosesgirl3) August 10, 2024

Examine The Evidence

The video has been shared and reshared on Twitter many times. A version was posted by reporter Jennifer Zeng on August 6, while a clearer version was shared by Pritam on August 9. When reposted by Science Girl, this misleading video gained over 9 million views.

Each car has these huge ballooning bubbles in its vinyl wrap, filled with many gallons of air. Roughly translated, the Chinese audio comments on how the vinyl has puffed up. The narrator says “This is not too bad, you can still see directly ahead,” referring to one of the hood bulges. The audio doesn’t tell us much about what’s going on, but the Chinese text tells us that this was apparently taken in Hubei province on June 5.

The prevailing theory from posters and the press is that a Chinese summer heatwave caused this problem. But that seems entirely unlikely if you run the numbers. Science time!

It’s true that small air bubbles in vinyl wraps are not unusual. Properly applying the film involves removing the air bubbles for a clean look, but it’s plausible that a hasty or lazy installer may have left some air bubbles behind. However, the idea that leaving these vehicles out on a hot day could create these huge bulging bubbles? That’s difficult to believe. Here’s some math to explain why.

Imagine that a whole quart (~0.94 L) of air was trapped underneath the vinyl wrap on the hood of one of these vehicles. That would be a sizeable bulge that you could never miss on sight. Nobody would accept a wrap with a bubble that big, but let’s be generous in our calculations. Imagine that air bubble was there when the vinyl was installed at a temperature of 68 F (20 C). If you then took that car outside on a hot day of 104 F (40 C), the air would expand. By how much? Only a disappointing 7%! Your quart-sized bubble would now be 1.068 quarts (1.004 L) in volume assuming the same atmospheric pressure.

Meanwhile, the bubbles we’re seeing are many gallons in size. That doesn’t check out. Basically, there’s no way heat alone could have caused these bulges. Air simply doesn’t expand enough to generate such extreme results.

Another theory put forth was that outgassing from the vinyl or adhesive caused this phenomenon. It is conceivable that breakdown under heat could release some gases from the vinyl, it’s true. However, it’s simply not plausible that a thin layer of vinyl could release so many gallons of gas—let alone while retaining its structural integrity and remaining visibly unaffected in any other way!

If you think critically and do the research, you’ll realize there has to be another explanation. Especially given that on June 5, the temperature in Hubei was only 79 F. Even as temperatures have risen closer to 100 F in recent days, that’s still not hot enough to explain anything. After all, Texas regularly hits those kinds of temperatures. There are plenty of wrapped cars there that survive without issue!

There is one thing, however, that generates bubbles in vinyl wraps exactly like these ones. Compressed air! In fact, blowing air under a vinyl wrap is a pretty common way to remove it. The typical technique involves inserting a compressed air nozzle under the corner of the wrap and inflating it to lift the wrap up from the hood. Head over to one of the many discussions on Reddit, and you’ll find a bunch of commenters from the vinyl industry saying just that.

So what’s the deal with this video? Well, I can think of two explanations. Somebody potentially saw these cars in the process of having their wraps removed, and simply assumed it was down to the warm local temperatures. Alternatively, it was a joke video put together that has been misinterpreted across a significant language barrier.

Out of extreme caution, I’ll say there’s an extremely tiny chance that there was some terrible batch of Chinese vinyl that maybe outgassed to some insane degree. But it’s hard to see how that would be the case. Especially given that most of the cars shown only show bubbling on one or two panels. You’d expect the vinyl to be bubbling all over if it was a heat-related outgassing issue.

It’s a shame that so many Twitter accounts—and news outlets—uncritically ran with this story about heatwaves and pregnant vinyl-wrapped cars. A bit of thinking and checking the weather forecast would have revealed all was not as it seemed! Of course, many newsrooms don’t employ engineers or scientists on their regular payroll, but it’s still important to examine exceptional claims like these before printing.

Ultimately, critical analysis and a bit of good old science will help you find the truth, even if Twitter is wrong. My engineering degree has never found me fame or fortune, but it’s given me the key skills to see through things like this!

Image credits: Pritam via Twitter screenshot