Different materials have different glossiness in surface. Because cotton fabric is spun directly from plants, so its glossiness is quite low, and it is matt on the surface. Polyester is the raw material extracted from petroleum and spun into yarn. Generally, its glossiness is matt. But its plasticity is very good. After heating treatment, its surface can also be made into bright and shiny, and its luster and color will change. Nylon, on the other hand, is bright, shiny, smooth and hard to make a matte surface. So if the backpack is made of nylon material, it must accept the fact that the surface is bright and shiny.