Trying to decide what %sh to put on a cement 2 story wall of a school. It’s not painted. There are some black streaks on it. Any suggestions?
Too many variables to know (especially without a photo).
Suggestions:
Search “concrete siding” on this site and see if anything comes up that looks similar.
Start low and work your way up.
Are the black streaks even organic?
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SH doesn’t fix everything. Dirt comes off with soap and water, organics (some) come off with SH. Other stuff comes off with other chemicals. Try spraying your HW mix in an inconspicuous area.
Racer put up a video of cleaning a school and he had multiple applications on the same place to get it clean. Go look for that.
need pics
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