The Opacity parameter controls the transparency of a material. The default setting is 100 percent opaque. An Opacity value of 0 creates total transparency.
Set transparency:
Do not save your changes.
The sample sphere becomes semi-transparent.
Opacity controls transparency.
The sphere becomes more transparent towards the edges.
The opacity falls off towards the center of the sphere, revealing a nearly transparent center.
The sample sphere takes on a ghostly look.
The areas of opacity turn dark like smoke, then light like clouds.