a method for creating a three - dimensional engraving within a solid . a three - dimensional illustration of the solid is scanned into a numerical controller associated with a machining center . the 3d illustration is projected into the solid according to individual depths of cut . the solid is machined according to its projected depths . shading is accomplished according to depth of cut and by immersing the solid into an oxide bath and successively abrasively removing a darkened coating according to depth of cut . powder coating with a thermoset plastic , baking and curing steps provide a transparent coating to the solid .