How Does It Work
Bubbles form because of water’s reduced surface tension due to the soap. Hydrogen atoms in a water molecule are attracted to oxygen atoms in other water molecules. They “like” each and they cling together. Soap molecules help them be more “stretchy” by butting in and decreasing the force of the attraction. Soap (and sugar) also slows evaporation of water molecules so bubbles can last longer. Why are bubbles round? Physicists will tell you that bubbles use a minimum amount of surface area to enclose the volume of air trapped inside.
Similar to the way we perceive colors in a rainbow or in an oil slick on water, we see colors on a bubble due to reflection and refraction of light waves off of the inner and outer film surfaces of the bubble wall. The rainbow colors and dark lines you see are the result of how the wavelengths of light are mixing after they leave the surface of the bubble. You can’t actually color a bubble since its wall is only a few molecules thick. A bubble can reflect color from its surroundings, however.
Regular bubbles burst when they come in contact with just about anything. Why? A bubble’s worst enemies are oil, dirt, and gravity. A “sugar” bubble will last a long time on a surface if the surface is free of oil or dirt particles that would normally break through or dissolve the soap film. Gravity is not a friend because it moves the film and water in the bubble downward so the film gets thinner and thinner on top and finally can’t hold together.
When you blow a bubble inside a bubble, you probably noticed the outer bubble expanding a little. When you blow the inner bubble, the volume of the air in the outer bubble is fixed and becomes compressed by the growing inner bubble. Did you follow that? The additional air not only causes the creation of the inner bubble, it forces the outer bubble to expand to accommodate the inner bubble’s volume as well. Thanks to the soapy and sugary solution, the hydrogen bonds in the water are elastic enough to allow for the increase in volume and compression.
A very important factor of the bubble solution is the water. Good quality water that doesn’t contain high levels of iron or other minerals or even purifying chemicals is best. If you’re uncertain as to the quality of your tap water, invest a small amount (about $1 US) in a gallon of distilled water from a grocery store or pharmacy.
