PIGMENTING Under the headings " Oil-pigment Process " and " Bromoil " have been indicated the means by which a print is obtained in gelatine relief, and in each case it remains to produce the actual picture by the application of a pigment or ink.
At least one brush of pole-cat hair, of fair size, is necessary, and smaller brushes will be found useful for local work. A small quantity of ink (a piece the size of a pea will be ample for even a is in. by ro in. print) is taken and rubbed down with the palette knife on a piece of clean glass or opal until of such a consistency that it can be spread on the glass in a thin film. If the pigment is too hard it may be thinned down with a softer ink, or with a trace of megilp or Roberson's medium. A thick ink tends to give hardness and brilliance, a thin ink softness. Black and Venetian reds are useful pigments, as by their use colours can be obtained ranging from black, through warm black, sepias and browns, up to red. The print is pigmented on a support made as follows : The foundation is a sheet of glass or zinc, or a pulp slab ; over this are placed two or three smooth sheets of wet blotting-paper ; and on top is stretched a piece of damp muslin. The soaked print is placed on this, and the moisture removed from the gelatine surface by gently wiping with a moistened pad of soft linen. A brush is now dabbed once or twice on the film of pigment, and then on a clean portion of the glass. The object is to secure that each hair-tip holds a minute trace of pigment. The charged brush is then applied to the print with a gentle dabbing motion, and if all is right the image will gradually appear as the gelatine accepts or rejects the pigment in accordance with the light action that has taken place on the bichromated gelatine. The print must be worked
upon patiently and systematically all over. It is best after each re-charging of the brush to work first on the stronger parts of the subject and then pass to the more delicate parts (such as the sky) when the pigment in the brush is diminished Gentle brush action and a thin ink will cause the print to accept colour more readily than a more vigorous dabbing and thicker pigment. High lights may be brightened by taking a clean flat-cut brush and " bouncing " or " hopping " it vertically on to the print. The more patiently the ink is applied in small quantities by con tinued and gentle dabbing the finer will be the deposit and the better the gradations of tone. Variations in brush action, the use of pigment of a different consistency, the ability to lighten or strengthen parts locally, all provide means of exercising control over the final result. But the beginner would be well advised to direct his efforts at first to obtaining " straight " prints with a fine deposit and a full scale of gradations.
The finished print is hung up to dry. The ink will set almost as soon as the paper is dry, but the prints should be carefully handled until the image is thoroughly hardened. The brushes should be cleaned immediately after use. This is easily done by rubbing their surface on a piece of fluffiess material moistened with petrol. The blotting-paper should also be dried after use or it will develop mould.