Science

Physicists work out the perfect soap mix recipe for blowing giant bubbles


Physicists have worked out the perfect soap mixture recipe for blowing giant bubbles — and the secret ingredient is a food additive called ‘guar powder’.

Looking to find out how soapy films fifty times thinner than a human hair can form bubbles stretching more than 10 feet long, the team tried different mixes in the lab.

They found that polymers — long molecules found in substances like guar powder — make bubbles stronger as their chains get tangled together and help resist popping.

The findings are not just useful for bubble-blowers, however, as they could help improve the flow of oil through pipes and the removal of foam pollution from rivers.

Scroll down for video

Physicists have worked out the perfect soap mixture recipe for blowing giant bubbles ¿ and the secret ingredient is a food additive called 'guar powder'. Pictured, the researchers blow enormous bubbles on a lawn in the Emory University campus in Atlanta, Georgia

Physicists have worked out the perfect soap mixture recipe for blowing giant bubbles — and the secret ingredient is a food additive called ‘guar powder’. Pictured, the researchers blow enormous bubbles on a lawn in the Emory University campus in Atlanta, Georgia

WHAT IS GUAR POWDER? 

Guar powder is a food additive.

It is used to thicken food, or as a source of fibre.

For example, it can be added to baked goods to improve dough, or ice cream to generate smaller ice crystals and therefore a smoother texture. 

It is derived from the guar plant, which is also known as the Lond bean.

The plant is grown primarily in northwest India and Pakistan, although crops are also cultivated in the plains of Texas, in the US.  

Pictured, a guar plant

Pictured, a guar plant

‘This study definitely puts the fun into fundamental science,’ said paper author and physicist Justin Burton of Emory University in Atlanta, Georgia.

Professor Burton and his colleagues study so-called ‘fluid dynamics’ — the flow of liquids and gases. 

‘The processes of fluid dynamics are visually beautiful and they are everywhere on our planet, from the formation and breakup of bubbles to the aerodynamics of airplanes and the deep-sea overturning of the world’s oceans,’ Professor Burton said.

The physicist was inspired to study bubbles after seeing street performers blowing huge ones using a soap solution and thick cotton strings.

‘These bubbles were about the diameter of a hula hoop and as much as a car-length long. They were also beautiful, with colour changes from red to green to bluish tones on their surface,’ he said.

The iridescent, rainbow-like colours that can appear on bubbles are a result of the thickness of the soap film being close to the wavelength of light — around a thousandth of millimetre, or a fiftieth of the thickness of a human hair.

This fact made the physicist wonder how such a thin film of liquid could stay intact over distances exceeding 10 feet (3 metres) — so he and his colleagues set out to investigate in the lab.

‘We basically started making bubbles and popping them — and recorded the speed and dynamics of that process,’ Professor Burton explained.

‘Focusing on a fluid at its most violent moments can tell you a lot about its underlying physics,’ he added.

The researchers tested out bubble mix recipes that they found on the Soap Bubble Wiki — an open source project that aims to help so-called ‘bubblers’ blow the perfect bubble by separating ‘fact from folklore’ around soap mix recipes and ingredients.

Many of the recipes on the wiki usually included a polymer in addition to water and dish-washing liquid, the team noticed. 

Polymers are substances made up of long chains of repeating molecules.

The most commonly-recommended polymers for making bubble mix included natural guar, which is used as thickening or fibre additive in certain foods, and polyethylene glycol (PEO), which is used as a lubricant in some medicine.

For each soap mixture they investigated, the researchers shone infrared light through the resulting bubble film to measure its thickness.

The team also determined the molecular weights of the different polymers used by each recipe and tested how far each liquid could stretch by letting drops fall from a nozzle and observing the thread of liquid that between droplet to nozzle.

Put together, the findings revealed that the polymers were key to making giant bubbles, with their long strands allowing the bubbles to stretch without popping.

For each soap mixture they investigated, the researchers shone infrared light through the resulting bubble film to measure its thickness, as pictured

For each soap mixture they investigated, the researchers shone infrared light through the resulting bubble film to measure its thickness, as pictured

‘The polymer strands become entangled, something like a hairball, forming longer strands that don’t want to break apart,’ Professor Burton explained.

‘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 researchers also found that using polymers of varied molecular lengths — as can form naturally when, for example, PEO is allowed to degrade over time — can strengthen the soap film even more

‘Polymers of different sizes become even more entangled than single-sized polymers, strengthening the elasticity of the film,’ Professor Burton explained. 

‘That’s a fundamental physics discovery,’ he added.

The team also determined the molecular weights of the different polymers used by each recipe and tested how far each liquid could stretch by letting drops fall from a nozzle and observing the thread of liquid that between droplet to nozzle, as pictured

The team also determined the molecular weights of the different polymers used by each recipe and tested how far each liquid could stretch by letting drops fall from a nozzle and observing the thread of liquid that between droplet to nozzle, as pictured

According the the researchers, developing a better understanding of how fluids and thin films respond to stress could lead to a variety of applications — such as helping to ensure oil flows smoothly through pipelines.

‘As with all fundamental research, you have to follow your instincts and heart,’ said Professor Burton.

‘Sometimes your bubble gets burst — but in this case, we discovered something interesting.’ 

The full findings of the study were published in the journal Physical Review Fluids

HOW TO BLOW THE BEST BUBBLES 

Physicist Justin Burton of Emory University in Atlanta, Georgia, has recommended the following recipe for blowing giant soap bubbles.

You will need: 

  • 2 pints of water;
  • 3 tablespoons of Dawn Professional Detergent;
  • 1/2 of a heaped teaspoon of guar powder;
  • 3 tablespoons of rubbing alcohol;
  • 1/2 of a teaspoon of baking powder.

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 to create giant soap bubbles. 

 



READ SOURCE

Leave a Reply

This website uses cookies. By continuing to use this site, you accept our use of cookies.