Thanks very much for the file Mark. The glass shader you created is brilliant and judging by the shader tree is more complex than what I've been doing. It shows I've a lot to learn really. I rendered the image and it looks great, so I predictably copied and pasted your glass shader to my empty glass (pictured). The shader is obviously designed to suit a wine glass and not a simple pint glass. I'll study the shader though and see what I can come up with. Thanks again for all the help. :)

Darren