This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
2. In the early days of photography, when the so-called "wet-plate process" was in use, prints were made direct from the negative without any alteration whatever, as the wet-plate rendered softer effects than are obtainable with the ready prepared dry-plate. The imperfections were less visible, and at that time the general public were satisfied with an exact likeness of themselves. With the advent of the dry-plate, however, the defects in the human face became more apparent on the negative, and there arose a demand for a greater softening of the lines and a removal of the more objectionable imperfections. At first, these imperfections or blemishes were removed, by means of a brush and color, from each individual print. So numerous, however, were these imperfections, and so irksome became the labor of eliminating them from the print, that the photographer was compelled to devise some means whereby he could apply these remedies direct to his negative so that each print made from the negative would have these blemishes eliminated. The results of these endeavors led to retouching the negative.
3. From the above we see that the object of negative retouching is to remove all the imperfections from the negatives, placing them in such a condition for printing that the
resulting prints will all be uniform, and no extra work will be required upon them after they are finished and mounted.
4. When photographers first began retouching it was done with brush and India ink, but they finally adopted the use of metallic lead, first grinding the surface of the film of the negative with pumice stone, in order to produce a "tooth," and then, by means of metallic lead, penciling over the objectionable portions. Later on, when the prepared papers came into use, it was found that the ground surface of the film was objectionable, as the grain reproduced in the print. After considerable experimenting a solution was adopted and applied to the negative, giving sufficient "tooth" to enable the use of an ordinary lead pencil for removing the blemishes. This solution is known today as retouching varnish, or "dope."
5. Probably one of the first solutions of the kind placed upon the market was Jewell's Retouching Medium, and today there are many mediums prepared after similar formula, all of which are good for the purpose.
Negative Retouching. The photographic negative, whether portrait or landscape, is seldom ready for printing immediately after it is dry. A certain amount of hand-work on it is necessary, and the process of correcting existing defects and building onto, or taking from, various parts is termed retouching and etching, respectively.
7. By retouching is meant the removal of all spots, blemishes and imperfections in the negative, as well as the building up of shadows, hollows, etc., that are visible; also the modeling of the features in a portrait, and the accentuating and strengthening of details in landscapes, architectural and commercial negatives. To accomplish this, we must apply some substance that will blend perfectly with the color of the plate. Some plates being more dense than others require a heavier or lighter application of this material. The negative being of a slate-brown color, the nearest approach to matching this tone is with the lead color; therefore, a lead pencil is employed for retouching.
It is not only very convenient to handle, but also very easily applied.
John H. Garo