• Soap bubbles dazzle the eye and attract people of all ages. The glistening reflections on their surfaces betray subtle changes in light. Although these fleeting objects display a mystery on their surfaces, the rules that form them are actually pretty simple and well understood. Made in the bath, shower or from the breathe of a bubble blower, all soap bubbles use the same rules to guide their formation.
  
  

Chemistry of the Soap

• Soap molecules have a hydrophilic and a hydrophobic end. The hydrophilic end is attracted to water, whereas water repels the hydrophobic end. The hydrophobic end will move away from the water, making the soap bubble rise to the surface. As more and more soap molecules rise to the surface, they will connect in a membrane (thin layer) with all the hydrophobic ends facing away from the water and all the hydrophilic ends facing toward the water. If another layer of soap molecules forms a membrane opposite to the first membrane, these two membranes have trapped a layer of water between them. This layer is the wall of a soap bubble--a wall that's composed of two layers of soap sandwiching water, all of which together have trapped a pocket of gas or air.
  
  

Surface Tension

• The behavior of surface tension turns the pocket that the soap and water caught into a sphere. Liquids seek to reduce the energy needed to hold their molecules together. In the layers of a soap bubble wall, the two liquids on the inner and outer surfaces--both soap--are attracted to the liquid between them, the water. This attraction pulls the soap layers toward each other, reducing the volume of the soap pocket. The smallest possible shape to house a pocket of air is a sphere. Thus, the soap and water will form a sphere, even if a strangely shaped wand was used to blow the bubble in the first place.
  
  

Improving Soap Bubble Formation

• The strongest soap bubbles come from special recipes of soap. The best soap solutions for soap bubble formations are made from detergents. Detergents don't have a carboxylate group, which other soaps possess and which interacts with the iron and magnesium in the water to produce a scum that prevents bubbles from forming.
  
  Humidity also promotes soap bubble formation, as do wet hands, because dry surfaces will break the hydrogen bonds needed to sustain the soap bubbles. In addition, glycerin is often added to soap bubble solutions because it forms weak bonds with hydrogen, preventing evaporation--the main culprit causing bubbles to break.