Bubbles

I want to make something realistic, and my first challenge is the shader and render of the bubbles. I made the Material on Arnold 5 using a ramp on the specular,

Bubble (Beauty)

Bubble (Specular)

Bubble (Coat)

Bubble (Beauty)

Bubble (Specular)

Bubble (Coat)

Bubble (Transmission)

Bubble (Wireframe)