Well WTB - Close but no cigar - at least you put me on the right track - Thanks - I changed the ambient to black rather than grey and got a clean render.

Wonder how that slipped by testing?

The supreme irony of life is that hardly anyone gets out of it alive.
Robert A. Heinlein

11th Gen Intel(R) Core(TM) i9-11900K @ 3.50GHz   3.50 GHz
64.0 GB (63.9 GB usable)
Geforce RTX 3060 12 GB
Windows 11 Pro