How to Remove Acid Rain From a Car Windowby Contributing Writer; Updated October 25, 2017
Water spots can prove to be an immense annoyance, especially when they make up for their small size with force in numbers. Acid rain spots, however, can prove to be far more troublesome in the long run. Often producing a cloudy or misty effect on the outside of the windows, acid rain actually can eat into your glass as it dries, and leave permanent marks. But even these stains can potentially be vanquished, with the appropriate methods. Read on to learn how to remove acid rain from a car window.
Clean your window as normal, with a lint-free cloth. Spots left over from acid rain are sometimes difficult to discern from simple water spots--with luck, your glass is only dirty, and not damaged. Follow up the initial wipe-down with an application of Windex. Try to let the window dry out of direct sunlight, in order to prevent ugly streaking.
Dust the spots with a thin layer of baking soda (sodium bicarbonate). Take a damp rag, and scrub the water spots with a liberal amount of elbow grease. The baking soda is an effective, readily-available abrasive medium that will remove the spots without damaging the underlying glass. For an extra abrasive edge, consider scrubbing with an old toothbrush. If the spots persist, however, move on to Step 3.
Apply a small amount of cutting compound to a super-fine (Grade #0000) steel wool soap pad. Cutting compound suspends an abrasive in a paste that can then be applied to your glass, and the soap pad will scrub more effectively than a simple cloth. Do a test on a small patch of glass before you apply this method to the whole window, to ensure that your window will endure treatment.
Attack any remaining spots with the same amount of vigor and elbow grease--acid marks can be incredibly persistent, and at this point you're polishing more than you are cleaning. After an appropriate amount of effort, check to see if any stains still persist. If stains are still readily detectable, try repeating this step while using a cutting compound of smaller grit size.
Assess the final result, after all reasonable effort has been exhausted. As the name suggests, acid rain actually etches into the surface of the glass. If the damage is extensive enough that it impairs the functionality of the window, you may have to bite the bullet and obtain new glass.
Consult your local repair shop to see how acid rain marks can be prevented in the first place. A preemptive application of baking soda, as in Step 2, may help to prevent acid rain marks from forming.