Over time, paint will get damaged by scratches, oxidation, swirl marks and etc. It's not something you can avoid even with regular waxing. Waxing only slows down the process and prevents it from being critically damaged.
Car polish are available in both abrasive and non abrasive types. But, generally, car polish is a mildly abrasive compound that helps remove these blemishes, clean, smooth and restore the sheen of the paintwork. Think of it like an exfoliating face wash; removing a layer of dead skin on your face.
How does Car Polish works?
Car polish removes a thin layer of the clear coat of the paintwork and levels it out with the surrounding regions to smooth out the paint with the imperfections. This will restore the sheen of the paintwork. The tiny abrasive particles in the car polish compound, when manually applied with hand and proper technique or with a buffing machine, will safely remove the defects from your paintwork even up to the extremely fine imperfections.
Depending on how aggressive the polish you use, usually it only removes around 5-10 microns of your clear coat and the clear coat of a brand new car is usually 30-50 microns thick.
Which type of car polish to use?
It is recommended that you use a non abrasive polish if you want to DIY the polish. If you really want to use an abrasive polish, make sure you know what you are doing and follow the instructions thoroughly since it will physically remove layers of your paintwork! 😨 Too much layers removed and you might be looking at quite a bill for paint restoration. Although now with modern cars now comes with a layer clear coat, it is still recommended to take precautions.
Tip for those who want to DIY: Stop polishing when your paint is already shiny. Over-polishing your paint might make it dull again.
Compounds vs Polishes
Compounds are usually more aggressive. These are mostly used to remove heavy scratching, paint oxidation and watermarks etching or sometimes, acid rain etching. Usually saved for paintwork that are in severe conditions. The heavier abrasive particles can leave behind micro-scratches of its own.
Polishes are less aggressive and are used to remove lighter scratch marks. They are also used to remove the micro-scratching from the compounds. Polishes can be broken down further into cutting polishes and finishing polishes.
Depending on the condition of your car paint, you can start on different levels, for example is your paintwork doesn't have heavy scratches, sometimes you may not need to use compounds and starting off with cutting polishes is good enough. Typically, you would go in the order of the most aggressive polish and work your way to finer polish.
Diminishing vs Non-diminishing
Diminishing polishes starts off aggressive, and as you work them, the abrasive particles will break down and it will become less aggressive.
Non-diminishing polishes however do not break down. The abrasive particles tend to stay on the same level of aggressiveness all the way.
Diminishing polishes will leave you with a finer scratches and sometimes may not even need a follow up polish unlike non-diminishing ones. However, because the abrasive particles in a diminishing polish do break down, you might not even have polished away your defects by then and will need to start over with another coat. So if you are looking at a very heavily defected paintwork, you might want to consider using a non-diminishing polish instead to help reduce the risk of over-polishing your paintwork.
How often should I polish my car?
If you maintain your car well, and it is regularly waxed, having it polished once a year is good enough. Polish lasts longer than wax in term of maintain the shine of your car. However, if you frequently find major scratch or spots on your car, you may need more polish work.
But do keep in mind that since car polishes are abrasive, do not over-polish your car. Usually your professional detailers are able to offer you some advices on how often to polish your car and how to maintain it. Polishes should also be followed by either a sealant or wax so you don't lost all that hard work way too quickly than its' worth.