Mac and Fellow Shadow Watchers,
I can't speak for other areas but
hereabouts the interglazing space in double glazing is filled with argon,
not air, from which it has a different 'refractive index' - I think my
physics teacher might have said if I'd had one. (WW2 - no teachers - just
nuns!)Does the maintained parallelism of an air/glass/air/glass/air interface still apply? My brain is starting to hurt again! Tony Moss
