Also known as photo-chemical milling, photoengraving is an engraving technique that makes use of strategies commonly associated with the processing of photographic images. The purpose of photoengraving is to aid in the process of reproducing images for mass distribution. As part of the process, an image is created which is then captured on a metal plate prepared for the purpose. That plate is next immersed in an acid bath as a means of etching the image on the plate. Once the plate is prepared, it can be used to produce multiple copies of the image.
There are several variations on this basic photoengraving process, with some having to do with the type of metal plate used to create the template itself. Both zinc and copper plates may be used for the process, each producing an image that is configured in slightly different ways. Depending on the nature of the image involved, such as a picture or an illustration, one method may be preferable to the other. In any case, the plate itself must be sensitized in order to allow the image to be captured clearly.
The process of photengraving involves the application of some type of material that is known as a photoresist. It is this material that is placed as a facing on the metal plate that actually serves as the medium to capture the image and make the etching possible. Exposure to ultraviolet light causes portions of the photoresist to harden into position, corresponding with the shading in the image that is to be captured. By immersing the plate in the bath, the portions of the photoresist that did not harden are washed away, leaving behind the image. To finish the final part of the process, the metal will be exposed to some sort of etching compound that dissolves the portions of the metal plate surface that are not still covered with the photoresist, resulting in a useful engraving that can be used to reproduce the image in a number of applications.
The use of photoengraving is common in a number of industries, owning to the many ways this process can be used to create etchings that simplify the creation of multiple images. Along with the creation of printing plates that can be used in the mass production of print media illustrations in books and other forms of print media, this process can also be used to create nameplates, engravings on a wide range of objects, and even aid in the creation of commemorative trophies and plaques. In recent decades, photoengraving has also been helpful in the creation of printed circuit boards associated with a number of different electronic devices.