Things are slow at the shop so we take time to oil and detail clean our machines. I am now onto cleaning and rearranging my work area. I have noticed some white stains on the concrete that are from the plate etch I use for our photo direct image silver master plates. I have tried every chemical in the shop to clean this up, nothing has worked. Some say to use a fine grade of sandpaper and then soak the spots in vinegar which is another acid that I'm uncomfortable using. I have tried deglazers, calcium eliminator, WD 40, plain soap and water, Windex, blanket wash, etc. Nothing seems to work. I'll try the sandpaper/vinegar thing next because I haven't tried that. Of course it stands to reason that another acid will remove an acid so maybe that will work. If any of you have any advice I would be happy to hear it.