The third coat, blue, is then put on for the finish, and here it is well to state that one coat of blue is rarely sufficient. It nearly always requires two coats of this colour to finish the picture. The first one is usually too light to give the desired effect. It may occur to the worker that one good, heavy coat would be sufficient, but this theory does not work out in practice. It is only a waste of pigment. Two some what thinner coats, or even three, will be found to be more effective. It is a rather difficult task to describe the develop ment of the coating of blue. If the first printing of this colour has been properly accomplished, enough may adhere to the sky and water portions of the print to give these their proper proportion, and, of course, where the blue covers the yellow patches left in the sky we shall have greenish-looking spots ; these should be carefully uncovered with a thin, soft stream from the hose or by careful brush work, but sufficient blue should be left to strengthen the effect of the cloud convolutions.
The water then receives our attention, and when we have taken off sufficient pigment to give us a slightly flatter tone than we have in the sky (this is helped by the deposit of yellow left from the previous printing), we then turn to the remaining portion of the picture, and, after washing out some of the excess blue from the trees, but not all, we give our attention to the grass, and note with pleasure the appearance of the yellow sunlight effect as we gently wash off the top colour. As we proceed with this we may find that our sky is too blue, so that we shall have to reduce its vividness still further ; in fact, it is necessary to observe constantly the effect of the last coat or coatings over the entire print, so that our finished picture will represent a harmonious effect. This point should really be emphasised; but, in order to secure a pleasing result, the three colours must be properly blended and at least a trace of each should be combined with the other two in every part of the print.
For further particulars, especially on the artistic side, we must refer the reader to Photo-Aquatint, by Alfred Maskell ; Practical Gum Bichromate, by J. Cruwys Richards ; or to Les Proc/des d' Art en Photographie, by MM. Demachy and Puyo.
Artigue's Paper.—A variety of gum paper, which may be
obtained ready-coated, requiring only to be sensitised before use. The vehicle is supposed to be a mixture of albumen and gum solution. Papier velours shows an extremely fine and delicate surface of velvety black, the coating being so thin as to be almost transparent and easily wiped off the paper by a stroke of a moist finger. From this fine, easily soluble layer of pigment arise the special qualities of the paper.
It is usual in sensitising to float the paper face upwards on the sensitising solution—a 5 per cent. solution of potassium bichromate with a few drops of ammonia. The sheet must remain in the dish until the sensitiser is judged to have penetrated through the back, no liquid being allowed to fall on the prepared surface. One minute is about sufficient. If very great care is exercised, both in immersing and drying, so as not to injure the sensitive surface, there is no reason why it should not be dipped like other papers of the kind. Drying must take place in a room where there is a fire and where the walls are dry.
Exposure is timed by an actinometer, although, owing to the transparency of the film, details are visible on the back, and development may follow immediately in water at the ordinary temperature—or in winter at 8oc Fahr. The image will often develop of itself, without any attention greater than rocking the dish. But if this does not suffice we must adopt Mr. Alfred Maskell's sawdust developer. A thick soup of finely ground sawdust is prepared in a wide earthenware pan. The paper is laid on a sheet of glass just above the pan, and a quantity of the sawdust mixture poured over it from a coffee pot or other utensil with a rather wide spout. At first only the lighter particles from the top of the mixture in the pan should be taken ; afterwards by dipping down, it may be taken thicker. This very soft rubbing seems exactly the right degree of force to use on the delicate surface of an Artigue print.
It was at one time thought that Artigue's paper would supersede carbon. There is no transfer, no temporary sup port, no hot water, nor any other of the special difficulties and complications of carbon. But, somehow or other, it has not " caught on " with the amateur, and is now rarely seen in this country.