Anyone come across it? I had a job a few years ago where there were weird 'cloudy' marks on the glass. Washing didn't get it off so I tried damp and dry scrim - still no joy. I concluded that it must have been on the inside surface (single glazing). The customer complained so I went back to check again - he insisted it wasn't on the inside and when I had a look he was right. I had another try on the outside but still couldn't get it off and it was only then he told me what it was
He'd had a break-in a few days previously.
Did a quote today and after I'd booked the job I noticed marks on the double glazing. Wet finger and hard rub had no effect so (having forgotten previous experience) I rang the bell and asked the householder to come and look. She watched me try to make some impression on it and when I couldn't she said it must be on the inside.
Left it at that but thinking later I remembered what had happened all those years ago. Coupled with the fact that she asked what the arrangement would be if she wanted to cancel (always gets alarm bells ringing!!) I phoned and told her that I thought the marks were finger print powder and that as we guarantee perfect results but in this case wouldn't be able to achieve them I withdrew my offer of service.
No argument, didn't sound surprised, just said "Oh, alright then".
I reckon she was just after a 'one-off' even though I told her we don't do them, and then she would have used the marks as an excuse not to pay and to cancel after the first time.
Lucky escape