Observe, then draw an empty transparent water glass and its cast shadow. As you look at the glass, look for the secondary highlight in its base and walls.
Fill the glass with water and look through it. Observe the distortion of the background and the change in the cast shadow. Also notice the increase in size of the secondary highlight.
Since the secondary highlight is the main distinguishing characteristic or transparent objects, it is sometimes helpful to accentuate it in your drawing.
Observe and draw several other transparent objects as well.
Which of these transparent objects is hollow and which is solid-and how do you know?