Soap bubbles

Everyone must have blown soap bubbles at some point in his life. They can be blown by use of a straw, a ring, or even a toy machine-gun. To get big bubbles, we should use a mixture of six units of water, 2 units of dishwashing liquid, and one unit of glycerine (it is available at the chemist'). The mixture should be left for some 6 hours. You can use a metal ring with the diameter even as big as one meter to blow gigantic bubbles, provided you have a big enough bathtub.

The bubbles blown from complicated frames e.g. a cube, assume unique shapes, minimizing the surface.

The question remains, why soap is added to make the bubbles long even though we know that soap decreases the surface tension of a liquid. It seems that by decreasing the surface tension, we weaken the forces that keep the bubble together in one piece. In fact, it is only after the surface tension has been lowered, can we stretch water in long layers. Without soap the cohesion forces are too strong. A water drop is indeed very dense!