Is there any proof they stay clean longer ?
If so can somebody direct me to it ?
Has anyone analysed it or done tests ?
I think there's a fair bit of anecdotal proof that WFP windows stay cleaner for longer. I've read much of it on this forum and heard similar from local window cleaners who use WFP.
Ian Giles cites an example with a group of shops he does that used to be a bit of dust trap - he's done them for years - and since going WFP he's sure the windows stay cleaner.
I suspect that's because with using good old Fairy, there's a residue left on the window that dust will stick to and that rain will mark.
With pure water, once it's dry, there's no soap residue for dust to stick to and for rain water to mark.
Remember, just because evidence hasn't been analysed or tested and is purely anecdotal, it doesn't mean it's rubbish.