Popular Mechanics, maaliskuu 1924
Numerous methods are suggested for coloring pictures to imitate firelight, most of them depending upon the staining of the entire picture with some dye, but few giving satisfactory results. However, a combination of dyeing and chemical toning will give a satisfactory effect. By staininig an entire picture light orange and toning the dark portions red, a fine imitation of firelight is obtained.
Any developing paper can be used. For the best results, the picture should be printed deeply; the print is first immersed in a bath consisting of 10 grs. of potassium iodide, and 20 grs. of potassium ferricyanide, dissolved in 1 oz. of water. This solution should be made in quantity as required, and the potassium must be the red prussiate crystals, not the yellow. The picture, immersed in this solution, will bleach away almost entirely, but must be left in the bath half an hour longer to convert the nitrate on the print completely into iodide of silver. This chemical is capable of taking up or "mordanting" many aniline dyes, but not all of them. The dye, which is red in case of firelight scenes, is then applied; lanafuchsine is the dye to use. After washing out the dye completely, another color such as yellow or orange, in the case with campfire scenes, is applied to the print to stain it completely and to deepen the red tint in the shadows. in this way the print can be dyed almost any color and tint desired. A good dye is necessary for successful work. The quality of any red dye can be seen when the print is washed; if any of the whites remain tinted, the dye should be rejected.
This process of coloring can also be applied to moonlight pictures of landscapes, using blue or green dyes, or even liquid water colors with a brush, as the print will take almost any aniline dye. It is not necessary to place the print in the dye, but better to apply the dye with a brush, paying no attention to the outlines of the picture, as the dye will act only on the chemical portion. If the dye is not strong enough after washing, a second application is made.
This process is also a splendid one for coloring lantern slides, as the silver can be dissolved entirely in an ordinary fixing bath during the process. The slides will be of a soft and delicate appearance and can be tinted with water colors afterward. A French experimenter recommends the following dyes: For red, lanafuchsine brilliante S L; blue, cyanol d'alizarine B F; yellow, jaune de quinoeline; green, vert brilliante d'alizarine; violet, violet lanacyl B.