Code 4351 applies to employers engaged in photoengraving.  Photoengraving involves the process of reproducing graphic material by transferring the graphic image photographically to a plate or other surface in etched relief for printing.  This classification contemplates photographing the image and the development of negatives used in the photoengraving process.

The process begins by placing the negative over a sensitized metal plate.  The plate is then exposed to an arc light, which causes the image to be transferred to it and developed.  Acid-resisting substances are applied to that portion of the plate’s surface containing the image.  The plate is then immersed in an acid solution and coated by brush with the acid eating away all nonacid-resisting material.  The plate is then refined by means of a rotating machine to remove excess metal and a beveling machine to bevel the plate.  The plate is then mounted on a wood or metal base to keep it even with the other type.  An engraver will usually clean the plate and perform any fine finishing which may require occasional hand engraving of additional designs.