Mary

Like your thoughts and insights.  I cannot argue with the fact that if we had regular cleaning of building facades the soiling would not develop to the extent it has.

I mean, the ludicrous bit is when you watch the window cleaners clean the glass of a window, and squeegee all the dirty detergent laden water down onto the frame or sill ... where it then sits.  No attempt to wipe down the frame members or the sill ... or in the case of flush curtain walls, no attempt to clean the aluminium or polished granite panels.

What a missed opportunity!

On more porous masonry buildings it becomes more difficult, because cleaning is actually quite difficult due to the fact that the soiling gets bound into the pores of the masonry.  Bit like stain removal from your clothes as distinct from the routine wash.

No time to get more detailed just now, but would like to consider this later and come back with some further thoughts.

Cheers

david