The two most permanent printing processes known are Platinotype and Carbon. The former will give either black or sepia-coloured prints, and the latter allows the choice of almost any colour to suit the subject. Black, brown, blue, green, and red prints may be easily obtained. For either of these processes the negatives require to be full of gradation and what is known as " plucky," that is, not too thin. In practice, it is a good plan to let the printing process which is likely to be generally used settle the kind of negative produced. For instance, if P.O.P., Bromide, or Gaslight papers are used, the negatives can be thinner than those required for the best results in Platinum or Carbon. The Gaslight papers are very convenient for many reasons. They can be printed, as their name implies, by gaslight or any artificial light, and no dark room is necessary for their development, which may be carried out in any ordinary room, if during the process the paper is kept some distance from the source of light and in shadow. The ordinary printing out paper, known as P.O.P., or the more recent P.O.P. self-toning paper, provides a convenient medium for proof prints from a negative when daylight is available.
A new process, known as " Ensyna," has quite recently-been placed on the market. It has been introduced by Messrs. Houghton & Co., of London, and can be printed by daylight or artificial light, and any colour from a bluish-black to quite a red may be produced simply by the different length of exposure given. No toning is required, the image being produced by physical development only, after which it is quickly fixed and washed. A finished print may be obtained in the short space of from six to eight minutes. The paper is said to be quite permanent and will probably prove a strong rival to the ordinary P.O.P. It may be had either with a glossy or mat surface, thus being suitable for all kinds of results. Enlargements may also be made on this paper, which is certainly an acquisition to the printing processes already on the market. For the production of artistic results a paper with a mat or semi-mat surface should be chosen. A print from a small negative which is required to show a large amount of detail will be best obtained on a glossy kind of paper.