Concentrated calcium or Lime scale
Often from an indoor parking garage, is caused by the concrete being cross-linked with water and calcium leaching out from the concrete, dissolving calcium hydroxide from the matrix. On contact with the atmosphere the calcium hydroxide reacts with carbon dioxide to form calcium carbonate and drips down from the level above onto the paint surface producing a surface stain.
When water drips off of concrete and onto your vehicle's paint, it brings with it a tiny bit of calcite and mineral deposits, and sometimes rust deposits causing an orange red stain from the concretes steel reinforcement (rebar), which dries on the paint when the water evaporates, leaving a light coloured streak that is not miscible. These types of stains should be removed as soon as possible
Correction- (a) to remove the lime residue from glass, carefully remove with a plastic razor blade
(b) Lime on paint or plastic can be removed with a weak acid chemical cleaner if caught early, use a 1:1 or stronger solution of distilled water/distilled white vinegar (Acetic acid) or try 3D Products 3D Eraser –made from biodegradable ingredients (Phosphoric Acid 10 – 15%, Deionized Water 80-85%) that will not harm your vehicles surfaces and if used as directed, it’s also environmentally safe. Use with very fine #0000 synthetic steel wool, for eliminating water spots on glass. Super fine synthetic steel wool works best for removing water spots from car windows. Do not leave on for long and apply in shade. The Gel like consistency prevents the solution from running down your car surface.
(c ) To remove any surface etching use a machine polish ( Optimum Polish, Optimum Compound)and a cutting (LC Orange or Yellow) foam pad (speed # 4-5.0 ) to level the surface (use the least aggressive polish/foam pad first, if this doesn't remove the problem step-up to a more aggressive set-up)
MSDS - http://www.3dproducts.com/msds/105W_Eraser.pdf