Editing Soap film (section)

==Drainage==

[[File:GenerationSoapFilm.jpg|thumb|upright|Figure 4: Picture of a film taken during its generation. The film is pulled out of a soapy solution and drains from the top.]]

If [[surfactant]]s are well chosen<ref name="Ball61">Ball, 2009. pp. 61–67</ref> and the atmospheric humidity and air movements are suitably controlled, a horizontal soap film can last from minutes to hours. In contrast, a vertical soap film is affected by gravity and so the liquid tends to drain, causing the soap film to thin at the top. Colour depends on film thickness, which accounts for the coloured interference fringes that can be seen at the top of figure 4.