Hi I'm a WFP newbie convert from trad and I do a stained glass window evening course. My tutor is on a job and is releading some windows. The diamond peices of glass now are out of the leaded lights now and the architect is giving him a hard time about them being clean. Although window cleaning isn't his thing as he repairs and makes up leaded lights, not cleans them. So he asked me to help as he knew I was a window cleaner. Anyway I got a 15th century manor house (watch out for falling masonary! and windows caving in!) and although they clean up lovely with wfp I got the same result with his test peice of glass. You cannot get rid of the cement mark (?) that runs where the edge of the leading should be/is. He wants some of my water, but I try to explain once he puts the glass in it'll contaminate it, it depends on rinsing with unpolluted pure water (sigh). Any suggestions on how to get rid of this line about 1cm in form the edge of the glass?