First we're going to make glass. It's very simple all done through layer-styles. All you have to do is draw a random #000000 sharp edge shape with the Pen tool.
Set the blending mode to Lighten.
Step two:
Add the following layer-styles:
Blend Mode: Lighten
Opacity: 24
Gradient: Default
Reverse: Check
Style: Linear
Aligh with Layer: Check
Angle: -90
Scale: 100