The Printing. The most delicate work in the application of the process for impression* made with fatty ink consists in printing from the plate when it is in a perfect condition to receive the ink in the exact proportions necessary to give the identical value of the negative. A good lithographer will soon become familiar with this operation, and he will plate is moistened and treated with two different inks or colors, one thick one to blacken the plate, and one having a brownish tone, which gives the half - tones. After every printing, the plate is again wetted and wiped with a rag, when the inking is proceeded with once more. If the plate gives but little half-tone in the shadows, a blind proof is taken off, which takes off the last remnant of the color, and then the plate is wiped once more and printed. A plate of this kind should furnish six hundred prints or more. The permanency of the plates depends upon due attention being given to their preparation, upon having gelatin that swells but little, and employing little force in printing. Some operators replace a portion of the gelatin with isinglass. This substance is to be obtained, as a rule, only of inferior quality, and is very dear; the bleached material is perfectly valueless, and the only quality to be recommended is the Russian.
It is well understood that this liquid should be passed over the plate after it has been cleaned with spirits of turpentine. When it is desired to give more brilliancy to the print, we may leave covered the blacks protected by the printing ink, and only wash the whites. The image thus will offer more contrast, but this effect is not maintained. According to the
The choice of colors is important. If a brown tone is desired, then Munich varnish must be added to the blank ink. This has the defect of coloring the plate, so that in the end it is not white, but brown. This varnish has the effect,also, of tanning the gelatin,and the printaeoonap-pear flat. A good brown mixture is afforded by the finest printer's black of the thickest kind, mixed with red oxide of iron and a little Casar varnish. To preserve the margins perfectly white, the negative is covered up to the image or design. On printing, fine tissue paper is cut into bands of two or three inches breadth, and these are put put on the edges of the plate, which are to remain dean before the printings - paper is applied.
Or a frame may be employed, the aperture of which represents the size of the plate, and over this is stretched tissue - paper saturated with paraffin, nature of the gelatin, and especially according to the more or less adherence of the film to the rigid support, the number of prints obtained from a plate may be set down at only fifty Off sixty, or it may reach from five hundred to one thousand, and even more. The care given to the printing contributes in a great measure to the duration of the plate. The rollers should be kept scrupulously clean and protected from dust or any hard grain which would infallibly mark the gelatin film. The cloths used in wiping, the sponge, the water itself, should be clean, so as to avoid stains and scratches. When the printer perceives that the print has a tendency to fog, it suffices, as we have just said, to make the gelatin film absorb a greater quantity of moisture; but, before wetting, any fatty ink that may have remained on its surface should be removed by washing with spirits of turpentine. The cloths used for wiping with the turpentine should be different, and kept in a receptacle separately from those used for wiping with water or the glycerin liquid. As much as possible fatty essences should be avoided, so as not to encounter too much trouble in wetting with water, which, otherwise, repelled by the fatty body, wets with difficulty the surface of the film, rendering it necessary to repeat the operation several times to render it complete. When the absorption of the water is unequal, we perceive marbled markings on the prints which injure the image, and which can only be removed by longer and more regular wetting. When this accident occurs, there often results a serious loss of time, and it is even necessary sometimes to abandon, momentarily, the stained plate to restore it to good condition, whilst another one is being printed from. The different kinds of paper used, the more or less pressure, and fulling, or underlaying, as the printers call it, are conditions of success or failure. It la, therefore, necessary to take all these details into consideration.
It is evident that a plate hiked in the same manner will produce different results, according as the paper is granulated or smooth, laid or not laid. In causing the pressure to vary, the result will also vary; it should be regulated so as to remove all the ink from the plate. Fulling, or underlaying, assists in obtaining this last result in those cases in which there are hollows to be filled by the paper. This fulling is obtained by placing between the cylinder and the paper to be printed on, some sheets of paper or a sheet of vulcanized rubber. If the surface of the plate does not offer any depression, it is not necessary that this fulling should be very decided. However, we advise to never use a substance that is too hard, such as fuller's - or bristol - board, in order to avoid accidents that frequently occur on the surface and an opening the size of the picture is cut out, and this frame of paper, made just the size you want the print to be, is laid upon the plate every time an impression is struck off. By this means a regular edge is preserved and all smearing of the ink upon the margin is avoided, two desirable things which should never be neglected.
361. After the prints come from the press they often need considerable "spotting out," which is done in a manner similar to that practised with albumen prints. They are then ready for delivery to your patron, provided he is content with a mat surface only. If the desire be to make them resemble albumen prints, so far as having a shining surface is concerned, then they must be varnished, which operation certainly adds to their cost, and lessens their liability to be injured by moisture more than of the plate when hard substances are carried either by the ink or the air in motion. If there is fulling, a portion of the effect will be produced in the thickness of the cushion, whilst in the contrary case it is the gelatin film which receives all the injury by a depression of the film, and then by a rapid removal of the surface, if the coating does not perfectly adhere to the plate. - Leon Vidal.