Okay guys. I have a buddy who I use to do car stuff with who runs a farm with his father. Where they do their plasma cutting and welding, the ceiling has collected some yellow scum. He can’t wipe it off with his finger in a video he took and sent me. It looks like it’s bonded with the metal sheet material. I was thinking something along the lines of a caustic degreaser, somewhat like we use for cleaning the oxidation off gutters but not too sure. Any suggestions?
Edit. 50 x 60 room. Has floor drains for water to escape.