After noticing fascinating street performers blowing giant soap bubbles, Justin Burton, a physicist at Emory University, was inspired to conduct a study. He was curious to find out what gives a small amount of soap the ability to stretch into a giant bubble. Recently, Burton and his colleagues completed the study in which they found out that mixing different molecular sizes of polymers within a solution is the key element of creating a thin film that stretches without breaking. This discovery in fluid mechanics could potentially lead to improving processes such as the flow of oils through industrial pipes and the clearance of polluting foams in streams and rivers.
More info: news.emory.edu | journals.aps.org
Recently, scientists perfected a recipe for making giant soap bubbles
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However, the study published in the journal Physical Review Fluids has some other practical benefits. Apparently, it has helped to develop a perfect recipe for making giant soap bubbles.
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A few years ago, Burton was in Barcelona for a conference when he got the idea for the study. His attention was caught by giant soap bubbles. “These bubbles were about the diameter of a hula hoop and as much as a car-length long. They were also beautiful, with color changes from red to green to bluish tones on their surface," he recalls.
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The scientist says that the rainbow effect shows that a film’s thickness is comparable to the wavelength of light, or just a few microns. It prompted him to investigate how such a thin film doesn't break when it's being stretched over a large distance.
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Giant Soap Bubbles Recipe
Ingredients
1 liter of water (about 2 pints)
50 milliliters of Dawn Professional Detergent, which is available online (a little over 3 tablespoons)
2-3 grams of guar powder, a food thickener sold in some grocery stores or available online (about 1/2 heaping teaspoon)
50 milliliters of rubbing alcohol (a little more than 3 tablespoons)
2 grams of baking powder (about 1/2 teaspoon)
Directions
Mix the guar powder with the alcohol and stir until there are no clumps.
Combine the alcohol/guar slurry with the water and mix gently for 10 minutes. Let it sit for a bit so the guar hydrates. Then mix again. The water should thicken slightly, like thin soup or unset gelatin.
Add the baking powder and stir.
Add the Dawn Professional Detergent and stir gently, to avoid causing the mixture to foam.
Dip a giant bubble wand with a fibrous string into the mixture until it is fully immersed and slowly pull the string out. Wave the wand slowly or blow on it and enjoy the physics of giant soap bubbles!
Image credits: emory.edu
The study, which took a year to complete, revealed that polymers made the long, fibrous bubbles.
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"The polymer strands become entangled, something like a hairball, forming longer strands that don't want to break apart. In the right combination, a polymer allows a soap film to reach a 'sweet spot' that's viscous but also stretchy—just not so stretchy that it rips apart," the scientist explains.
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