bluestone and tree sap
I searched prior posts for cleaning bluestone, but no one seemed to have tree sap as the issue.
I've tried scrubbing with bleach/water, alcohol, orange stuff for removing sticky things, fingernail polish remover, and bug and tar remover made for cars. The most that happened was that the white sap turned gray, but it's still there. The only thing that worked was scraping it off with the tip of a screwdriver. That might be an option, except there are so many sap drops over such a large area, that it would take me months!