Hi all, just lost three jobs as the upvc frames had black marks all over them. This appears to have come from the black rubber beading ( seals ) that is between the glass and the frames. Infact when running my finger over them in the dry my finger tips are coming away black. I'm woundering whether this is because the beading is old. It's not happening on other houses just these three. Any ideas appreciated and any ideas how to get it off the frames please. Going back out to work now, came home to put this up as I panicked.