School of Physics Lecture Demonstration Manual

Fb-5 Minimum Area of Soap Film

Published: Friday 10 March 2006 - Updated: Tuesday 29 March 2011


To demonstrate that liquid surfaces tend to shrink to the smallest possible area.



Click on pictures to enlarge.

Min Area of a Soap Bubble Diagram


If the wire frame A with the cotton loop attached as shown is dipped into the soap solution, a film is formed and the loop keeps its irregular shape. The loop becomes circular when the film inside it is broken with the aid of a needle heated in the flame of a match.

A film is produced on the wire frame B and the curvature of the cotton can be altered by the force applied at F.

Various prisms and pyramidal frames are available to demonstrate the minimum surfaces generated when dipped into the soap solution. The surfaces are strikingly beautiful.

Safety notes

Electrical Safety 

Chemical Safety 

Fire/Burn Safety 

Personal Protection 


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