For some reason chems work different here our climate is very dry and we are high altitude. The guy that sells me the chems runs a shop in Utah also, and they dont seem to get the results that I do out there.
They get it pretty clean, but we have been cleaning this location since July, and the area looks better each time you do it. You will probably never get it all the way clean. Also it depends on if they have ever had it done before and how long the stains have been there.