The longevity of a soap bubble is limited by the ease of rupture of the very thin layer of water which constitutes its surface, namely a micrometer-thick soap film.
It is thus sensitive to :
* Drainage within the soap film: water falls down due to gravity. This can be slowed by increasing the water viscosity, for instance by adding glycerol. Still, there is an ultimate height limit, which is the capillary length, very high for soap bubbles: around 13 feet (4 meters). In principle, there is no limit in the length it can reach.
* Evaporation: This can be slowed by blowing bubbles in a wet atmosphere, or by adding some sugar to the water.
* Dirt and fat:  When the bubble touches an object, it usually ruptures the soap film. This can be prevented by wetting these surfaces with water (preferably containing some soap).
After experiments, researchers found that a solution containing:
* 85.9 % water
* 10 % glycerol
* 4 % dishwashing liquid
* 0.1 % guar gum
gave the longest lasting results as it minimised the Marangoni Effect.