Reproduction of portraits on metal surfaces - using rows of shallow holes with size proportional to degree of shade

摘要

A method of reproducing a portrait on the surface of a precious metal for making jewellery, begins by covering the portrait with a network of parallel lines to make rows of squares. Each square is marked with a number from 1 to 5 corresponding to the degree of shade from white to black. The grid is then reproduced on a metal surface by making a series of shallow circular holes in which the sizes of the holes correspond to the degrees of shade. The holes are then filled with colouring matter which contrasts with the background.