Ok guys, I will give you all the information you can handle regarding etching.
Basically there are three way you can receive etching on your clear coat. The first is from bird droppings, second from acid rain, and lastly from hard water. I am sure you can put two and two together and see the trend of acidic properties. Because birds have pee and poop in one squeeze, this makes their fecal matter more acidic. Also depending on how close you are to the ocean or how far away you are located from "salt water" will tell you how acidic the elements are. Anyone located close to the ocean will have a greater chance of etching due to the higher acidic levels. With water, it depends more on your underground water tables. If you have well water, then you will have a higher calcium content and this will cause "water spots" that if not taken care of quickly can turn into etching. Acid ran is less likely to happen and I have yet to deal with any clear coats that have been eaten by acid rain therefore I would rule that out in my cases. So in conclusion if you live close to the ocean, have bad water, or have a high bird population; be more careful and keep your eyes peeled.
The best offense is a good defense. Keep your car sealed and waxed as much as possible. I would recommend a good seal every 3 months and a wax every month. It is also a good idea to keep some QD and a MF towel in your car, so if you get some bird droppings on your car, you can take it off quickly therefore lessing the chance of etching. Still you would like to wash your car as quickly as possible after you have contamination.
As far a etching goes, it needs to be machine buffed out. Etching is when your clear coat has been actually eaten away by acid, therefore leaving a haze and a little dimple in your clear. Clay will get some of the haze and contamination off, but to get the actual etching off you will need to buff it. With any etching as far as bird droppings, water spots, ect it is always a good idea to clay first. For example with water spots it is mostly caused by cal cum build up which under a microscope looks like little sand molecules. If the calcium has not been removed before buffing those little sand molecules will scratch the paint thus making the detailer have to take off more clear than needed. For some water spots and etching you can use a product like ScratchX that is abrasive and will take some of the crap off, but I buff everything. A great product that can be used while washing is CG Water Spot Remover and is designed to remove the cal cum build-up and other contaminates.
I can elaborate for hours, but knowledge is power and I want to let you guys know what causes it, and the best way to take care of it. If I had etching this is what I would do, or what I would make sure my detailer did to properly take care of the problem:
Hope you guys find this informative and helpful!
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