The plate is then carefully compared with the original copy and after any necessary corrections have been made it is gone over by an expert operator, who cuts out any of the channels which may have been obliterated by the burr of the wax, resulting from pressing in the names.
We now have a plate in which the lines have been cut in small channels and the names stamped with type. This is a matrix, or mould, from which an electrotype of the lines now sunken in the wax may be made in high relief for printing, but the blank portions of the wax are so thin that it is first necessary to fill in all these places on the plates with wax in order to produce a sufficiently deep electrotype plate. This is done by "building up" the plate. A small hook-shaped tool, heated over a gas jet, is used to melt small pieces of wax which are run carefully around all the names and in the spaces between lines, thus filling up all these spaces with a round, smooth body of wax. From this mould an ordinary electrotype is made by the method described elsewhere in this book.
All these operations require much skill and patience at every step, but the plates produced by the wax process are always much deeper and stronger than those made by any other process.
The method by which a photogravure plate is produced, is probably the least understood of all of the many photo-processes of reproduction. This is chiefly on account of the difficulty of the process, which is not an easy matter to explain in detail, and also on account of the secrecy with which all plate makers guard their processes.
The reproduction of a mezzotint or line-engraved print, when made by a good photogravure process, produces in most cases a print which cannot be detected from the original. The originator of the process was probably Fox Talbot, an Englishman. The writer has seen one of his prints, made between 1855 and 1860, which was a very creditable piece of work. Dujardin of Paris took up Talbot's process, and after much modification, succeeded in developing a successful process which he is working to-day. All photogravure plate makers of the present time have more or less copied the process of Fox Talbot.
There are three different methods of making these plates known to the writer. The reader probably knows that a photogravure plate is not a relief plate, but an intaglio, and is printed on an etching-press in the same manner as an etching and requires special skill in printing on the part of the printer to produce the best results. I will give a brief explanation of the three different processes.