[Aunty Betty]

Apologies to my seemingly dumb question guys - I've never ever used glass in any render before.

Grendel thanks for that tip and indeed I'd been checking out 3D extract for some speed tips etc earlier on.

molaram - thanks for clearing that up.

Couerl - many thanks for your further suggestions.

Well as usual I can see from tests there's that discrepancy between reality and an artistic reality of a material such as how the impressionists may have rendered glass or indeed most painters. I'm trying to find a happy medium as I don't want the complexity of the surfaces to overpower the overall impressionistic effect.