As a Measure of Durability. Almost all polishes, waxes, etc. bead water initially. As they are removed, breakdown or dissipated by washing, exposure to sunlight and heat, expansion and contraction, abrasion, abrasion from pollen and other pollutants, the water beading is diminished. This is due to the reduction in surface tension of the polish or wax once it is removed or breaks down. If the surface has any protection when there is no water beading is the subject of much controversy. Especially when the polish or wax exhibits good water beading immediately after the initial application. If there is any protection left, how would one know? There are no scientific tests to my knowledge that can determine this. Most consumers and especially wax/polish manufacturers use the reduction in the height, contact angle and diameter of water beading as a gauge to know when to re-apply polish/wax for continued protection. If a polish/wax gives water beading initially but then stops beading after washing, part of the polish formula has been removed. If this happens, is there any protection left???? Was the chemical or film that caused the water beading also the protection???? If a manufacturer claims that their polish/wax will bead water initially and then magically change to sheeting… I say impossible!!!! Let them prove that the polish/wax film protection initially applied is still there… Until a specific test is developed and not some fake, razzle-dazzle test, these questions will remain unanswered and I will continue to use water beading, (height, contact angle and diameter) as a major factor in gauging a polish/wax protection. P.S. Please remember that healthy paint will bead water without any polish/wax applied. This confuses many people to believe a polish/wax is lasting longer than they think. To test your polish/wax, you must measure the water beading of your paint (height, contact angle and diameter) without any polish/wax applied. Next, measure the water beading of your paint (height, contact angle and diameter) within 24 hours after initially applying your polish/wax. This is your starting point. This will also be the gauge for determining the water beading (longevity, duration and changes) for that specific product. As the water beads start to diminish (get wider and shallower and loses contact angle), the polish/wax and its film protection factor is going away. When the water beading is the same as before you apply your product, the polish/wax and its protection are gone.