Steve wrote in
:

https://www.mclendons.com/item.asp?s...&subcat1=Cemen
t+-+Grout+%26+Mortar&subcat2=

Can you scrape it with a single edge razor blade in a window scraper? Yep,
you may still see a residual mark even after scraping in certain light. Not
sure how to remove this. Maybe buffing with a machine.

Instructions for the stuff I used said to make sure to wipe up excess
within 5 min with absorbant towel then a light hand buff with a cotton
towel...to avoid residual marking.