@ dazi dont know what oxidised frames are?!

i did used to do them trad and as i recall i dont think they hda hard water marks on them, but i cant be 100% on this!
they are upvc frames(white)
i doubt its on the insaide but again i cant be 100% on this either
when i rinse glass i rinse from the top of the glass
they dont clean them inbetween me doing them as far as i know again cant be 100% but doubt it very much mate!
there not on a main road!
i already do clean all my houses wfp top trad bottom!
some good ideas there mate thanks once again, GB