Are multiple coats of wax beneficial? (Layering)
That depends on what effect you are looking for: protection or beauty.
Protection
If your looking for the maximum protection possible, then one or two thin coats of wax, maybe even up to three thin coats of wax, has the potential to create the most surface protection depending on the wax, the surface itself and whether or not sufficient time has passed in-between each application. Of course the law of diminishing returns states that you will not create exponentially greater layers of protection with each application, but Meguiar's knows that a second, and sometimes third application will insure uniform, thorough coverage over the majority of the surface, thus maximizing the protection.
Environmental conditions today demand more frequent washing and waxing in order to prevent costly damage to the outer layers of paint. Just as important as a second, and possibly a third coating of wax is to provide the maximum amount of protection in any one detailing session, (especially on the horizontal surfaces), it is also vitally important that you wax more often to maintain your finish. This is especially true if your car is a daily driver exposed to the elements and parked outdoors most of the time.
Beauty
Will more coats of a product make a finish deeper, darker, and wetter looking with each additional application?
In a word: Possibly
Generally speaking, when trying to take your car's finish to its maximum potential for clarity, gloss, shine and depth of color, there comes a point, or a plateau, that you will reach whereupon additional applications of either polish or wax will not increase the results of any of those categories. Of course, you are more apt to reach this plateau if your skill level is high and if the quality of your products is also very high.
These assumptions also assume that the surface in question is on
* A brand new car
* A car with a brand new paint job
* An older car whose finish has been well maintained and is in excellent condition
* An older car whose finish has been professional restored to excellent condition
If any of the above holds true, then you will most certainly hit the wall, so to speak, reaching that plateau of perfection whereby further applications will not improve the results of the previously applied coating. Your finish will have reached its maximum potential in appearance value.
After time goes by and this plateau you have previously reached begins to diminish, you can restore the paint to it's maximum potential again, quickly and easily by simply applying a new coat of the right wax or polish. This maintenance procedure will only act to restore the finish back to it's maximum potential and shouldn't be positioned, or confused with making your surface deeper, darker, shinier, etc. than it's maximum potential.
Once you hit 100% max potential, (or that plateau), it's time to stand back and admire the results, not continue to apply more and more coats.
Special Note: Ideas suggesting that repeated applications of a product will continue to increase optic clarity and gloss and protection are misleading you and your own common sense should enable you to understand that a finish, whether black, red, single-stage, clear coat, etc. has a limit to how perfect it can become. 100% of 100 is 100
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