Why does soap make bubbles disappear?

[Velvetee]

Why do bubbles in a bubble bath disapperar when they come into contact with soap?

My partner says it's because soap has a high salt content and this destroys the bubbles. Is this true?

[tigersam258]

i think its to do with the alcohol content in the soap.

[rojash]

Soap contains surfactants whose purpose is to break the surface tension of the water - bubbles depend on surface tension to sustain themselves.

[Dr. Suds]

It's not salt content per se. Lime soaps -- the water-insoluble soaps that form when soap is dissolved in water that's at all "hard" (limey) -- are potent defoamers. This is seen not only in bubble baths but also with beer in glasses that have been washed with soap in anything but completely "soft" water. It has also been taken advantage of in formulating some laundry detergents -- counteracting foaming by incorporating a small amount of soap so the foam breaks faster.

In water that has no available calcium, magnesium, etc., soap only adds its own lather to the foam of a bubble bath.