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.
629. In order to centralize the light on the point of interest, the advanced student tries many ways to cut down objectionable high-lights in his picture, all of which are more or less successful. One of the most practical methods of doing this is by locally developing the negative, by which is meant holding back where the accent is not needed, and allowing full development where the interest is centralized. This, of course, applies to that class of work where lights are the point of interest. To do this, three separate developers must be used; one the regular straight formula, another the straight formula with the alkaline solution left out, and then a simple solution of one-half water and one-half alkaline solution. Put two brushes (soft camel hair) in the latter, one about one inch and one about one-eighth inch. These sizes apply particularly to 6 1/2 x 8 1/2, or 8 x 10 negatives.
630. Now, we will say that your exposure is made. The subject is a woman in white drapery, or white dress. Lay the exposed plate in the tray, and pour on the normal developer as though you intended developing regularly. Now, just as soon as the image becomes visible, rinse the negative in water, and place it in the second solution, which is minus alkaline. As it will not continue developing to any extent in this solution, you may now start your local work.
631. First, go over the whole negative (quickly) with a large brush saturated with the alkaline solution, being careful to cover all parts. Addition of alkali starts development again. To do this, hold the negative in hand, and immediately when you have covered the plate with the large brush, place it back in the tray No. 2 for a few seconds, then take up again. Use a small brush to develop the high-lights, to give accent where you require. This gives the opportunity of bringing out or holding back any points you wish in any part of the negative, as only those parts of the negative to which you have applied the alkali (carbonate of soda) will develop. The operation of brushing should be repeated until the negative is sufficiently developed, always immersing the plate in bath No. 2 after applying the alkali, as it requires the two combined to carry on the development.
632. It will be found that the system and solutions can be varied to suit effects desired, such as, use one-third alkaline solution to two-thirds water, or two-thirds alkaline to one-third water. Over-timed negatives are very difficult to manipulate locally, and in such case it is suggested that a very weak solution be used, or the negatives will develop too rapidly for proper control. Also, it the water used in making up developers is very hard, the alkaline solution must be stronger, or very slow development will be the result.
633. In making home portraits a window often comes into the composition of the picture, and if developed straight would take a most prominent position, detracting from the interest of the subject. Under such conditions local development gives perfect control, as it is possible to give one-half the development to the window, while developing the rest of the negative to its fullest extent. The following formula for brush development is found to be the most satisfactory: