Because the small hole on stainless sheet causes the ink to screen, while finishing the ink drop down into the hole, making a darker alternate surface.
Due to the small hole on the sheet of stainless steel. While the ink to make the cut screen. Ink dropped into the hole Make darker than other surfaces.
Since the birth of the small holes on the sheet of stainless steel. Do while cut ink to screen ink fell in the hole. Make a darker than other surfaces .