ILLUSTRATIVE PROCESS-WORK 255 



The Rubber O/set Machine is being installed somewhat largely in printing establish- 

 ments. It is an adaptation of lithography, and the principle of it is that, instead of 

 printing from the lithographic stone or metal plate direct onto the paper, the inked 

 print is impressed upon a sheet of rubber, stretched over an intermediary cylinder, 

 and from thence is transferred, or " offsetted," on to the paper, which is carried round 

 the impression cylinder by grippers in the ordinary way. 



The offset method can be applied to flat bed machines for printing from stone, but 

 usually the machine is rotary, and prints rapidly, as many as eight thousand impressions 

 per hour being obtained when the machine is mechanically fed. The results are 

 excellent, the finest lines and dots of the process block being reproduced on almost any 

 quality of paper. It is somewhat of an irony that lithography should come to the 

 help of its old enemy the half-tone block. A good deal, however, has still to be done in 

 improving the quality of the inks used for the offsets, in securing rubber which shall be 

 more sympathetic with the inks, and in other directions. 



Transfers from process blocks are not so rich and full in colour as could be desired, 

 and successful experiments have been made in the use of intaglio plates for this transfer 

 process. An ordinary half-tone negative is made, from which a positive or transparency 

 is prepared. This positive is etched on copper or zinc in the same way as for a photo- 

 gravure. A print is pulled from this plate in lithographic ink, which is transferred to 

 the zinc or aluminum plate for printing on the offset machine, and an impression taken 

 therefrom is offsetted on to the rubber sheet, from which it is printed on any quality of 

 paper, with admirable results, the colour from these offsets being rich and velvety similar 

 to those produced by the Rembrandt photogravure work. 



Up to the present three-colour work by the offset machine has not been so successful 

 as black and white. The coloured inks are a greater difficulty, and the true register, 

 so necessary for three-colour ink, is far from a certainty. When these difficulties are 

 overcome there will be a vast field of operation open to this new development. 



The Mertens Process. A most interesting application of this use of intaglio gravure 

 with letter press has been made in Germany by Dr. Mertens, who for newspaper work 

 has coupled up his rotary intaglio printing machine with a rotary newspaper machine. 

 The paper from the roll or web first takes the impression from the intaglio plate, passing 

 on to the type machine which prints the letter press from the stereo plates. The two 

 machines work of course at the same rate, and the result is a newspaper in which the 

 illustrations have the rich qualities of photogravure work, produced (it is claimed) at a 

 rate of twelve thousand an hour. 



Coupled Up Machines are being applied to the printing of three, four or more coloured 

 work. The machines to the required number of colours are coupled up to one driving 

 shaft, and the sheets pass from one machine to another, all the colours being printed 

 one after another in quick succession, instead of each colour being left some hours to 

 dry before imposing another. The use of dryers in the specially prepared inks permits 

 of a second, third or fourth printing following immediately on the first without producing 

 the muddy effect resulting from the admixture of two colours both equally wet. The 

 invention has greatly extended the possibility of the use of colour blocks for ordinary 

 illustration by reducing the time necessary for the printing of large editions. 



An interesting application of the Rembrandt intaglio process is in the direction of 

 colour work. Attempts to print colours on the rotary intaglio machine have not been 

 successful owing to the difficulty of obtaining accurate register on a rotary, but a com- 

 promise has been effected in what is known as the Widdop process by printing the 

 colours lithographically from stones or plates over a gravure print. The results are 

 rich, and blend very harmoniously with the soft monochrome of the gravure print. 

 Reproductions of watercolour drawings by this method are particularly successful. 



The success of the Rembrandt photogravure process has produced many rivals. 

 Most of them work on the principle of the rotary machine, but an interesting develop- 

 ment not far advanced at the present moment, though full of promise is that of 

 flat bed machines for printing gravure plates. 



