Ah, sounds a very good tip. I would never have thought of that.I’ve also found for Whites a polarising filter is very effective.
It would be intriguing to photograph whites in ultra violet as apparently they would take on a delightful blue colour. I have a "black light" (for moths - doesn't work very well) that makes white clothing glow (disco style so I am told) so that could be very effective for experimenting with whites.
Now to search for my old folding net, last used many years ago for Essex/Small Skipper counts – the net is doubtless hiding in the garage somewhere. I'll catch a white or two, then try to pose indoors in the dark except for the black light.
Jack