So, you want to blow a giant bubble?

According to the Guinness Book of World Records, the largest blown free-floating soap bubble currently stands (the record, the bubble has since popped) at 96.27 m3 (that’s a whopping 5.7 m diameter!). To put that in context, a bubble that size could hold an entire Volkswagen Beetle. In terms of the longest bubble, the world record stands at 32 meters, that’s longer than a basketball court! One could even say its..unbeleivabubble.

As large as these bubbles are, they somehow maintain a wall thickness of only a few microns – that’s one one-hundredth the thickness of a sheet of paper. So why can such fragile bubbles grow to such large sizes? A team of physicists at Emory University is working on it.

The author’s recreation of the world record largest bubble.

While at a conference in Madrid, physicist Justin Burton was walking the streets when he came across street performers blowing massive soap bubbles. Upon returning home his sister bought him a bubble wand. Burton wondered, what kind of natural forces yield such large bubbles, and how can they stay intact for such a long time?

I love bubbles and the world loves bubbles—we buy over 200 million bottles of the product annually. Maybe it’s because bubbles captivate our imaginations, their iridescence turning ordinary sunlight into a psychedelic light show. It’s no wonder street performers are turning to bubbles to make mind-bending art.

For some, bubbles are an afternoon of enjoyment, but for others, they’re so much more. The Soap Bubble Wiki connects bubble enthusiasts across the globe, providing the chance to exchange recipes, recommend tools, and learn the soapy science behind bubbles.

While blowing a big bubble is certainly fun and brag-worthy, the study of soap-based films is far from trivial. In physics research, soap bubbles can serve as vital models for larger processes. They’re also important in educational models. When a bunch of bubbles coalesces to form foams, they can become a powerful force, whether it’s in a can of soda, a fire extinguisher, or a volcanic eruption. Studying the stability and longevity of such foams is important to understanding our environment.

An alternative technique for blowing a bubble, as described by a particularly loquacious marine invertebrate.

But to understand the foam, we must first understand the bubble. And to understand how to make a bubble, we must first ask, what is a bubble? We must observe the bubble, we must be the bubble. Let’s break it down:

The film of a bubble is usually composed of a soap-based solution. Soaps and detergents are classified in a category of substances called “surfactants”, which reduce the surface tension of the liquid that they’re added to. Essentially, this is what allows the soap to stretch and disperse. Next comes the long-chain polymers. If you’re looking to try this at home, look no further than a container of guar at your local health food store. Guar gum comes from a bean and acts as a

thickening agent for foods and industrial mixtures. Although I wouldn’t eat these bubbles if I were you…

It takes about 300 ml of liquid to make a bubble over 100 m3 and break the world record. To do this, your bubble mixture must be perfectly balanced. It must be elastic, but not too stretchy. The fluid must flow, but not flow too much.

For their experiment, the researchers created various mixes of water, soap, and long-chain polymers to make their bubbles. Unfortunately, blowing a 100 m3 bubble is a poor use of lab space, and quite difficult to measure accurately, so the soap films were created using a cotton string, and the thickness was measured using infrared light. In addition to measuring the thickness, they also tracked the lifetime of each film.

Interestingly, one factor that strongly determines the size of a bubble is the mixing of polymers with different molecular sizes. The larger the difference, the more a bubble can extend. It’s still not clear why this happens, but it means that fewer polymers need to be added to create an ideal bubble mixture.

So, what does this all mean for the casual bubble fan? When you’re choosing a day for bubbles, a warm and humid summer afternoon is a perfect time. In an arid climate, the water along a bubble film will begin to evaporate, progressively thinning the bubble until a hole is developed, and the bubble pops. If you’re looking to maximize your bubble, I’d strongly recommend taking a trip to Florida.

In the future, this research could lead to developments in bubble mixtures and could change our understanding of how soap-based films work. In the grander scheme of things, sometimes the most random experiments lead to huge scientific advances. We never really know what will spark the next discovery.

“Just follow your curiosity, you never know where it will lead,” remarked Burton on the research.

Where will your curiosity take you?

—Lissie Connors

Lissie Connors is a graduate student studying earth science at the University of Oregon. She’s a regular contributor to Physics Buzz, writing about anything from space plasmas to electric eels.

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