It is designed through a multi-action method, beginning using an anodization section to make the floor from the casing a porous aluminum oxide, after which using a machine to brush the casing via a powdered compound, absorbed by aluminum oxide. The process is concluded with an "ultrafine particle bathtub" https://social4geek.com/story13437019/facts-about-iphone-7-plus-c%C5%A9-revealed