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.
Intensifying. The intensifying of a negative is the building up of a negative which is thin and transparent - due to either over-exposure or under-development - and making it more opaque. Any amount of density can be obtained, and if your first efforts do not produce the desired strength immerse the negative again in the intensifier until the desired density is obtained.
306. (See Illustration 32.) In this illustration we demonstrate the advantage of intensifying thin, flat negatives - those which would give dull, flat prints unless strengthened. In order to demonstrate more clearly the advantage of intensifying, we have intensified only half of the plate, leaving the remainder untouched. Note the difference.
Intensifying Powder. For the convenience of the beginner we recommend the use of the prepared intensifying powders or solutions, which can be purchased from any dealer in photographic supplies. Instruction for the use of such prepared powders accompany each package, the usual requirement being to dissolve so much of the powder in so much water, when the solution is ready for use. The bottle containing intensifier should be carefully labeled "Intensifying Stock Solution," and when not in use should be kept well corked and placed away in the dark-room.
308. This solution can be used repeated until completely exhausted. It is advisable to use only a portion of the solution at a time, sufficient to cover the negative completely - 3 ozs. is ample for a 4 x 5 plate. After the negatives are intensified the solution should be returned to a bottle labeled "Intensifier for Use," and always use from this bottle. Add enough of the fresh stock solution from time to time to keep the bulk to about 3 ounces, or sufficient to completely cover the plate.
Intensifying The Negative. The negative to be intensified must be thoroughly washed, to free it from hypo, before placing in the intensifying solution. Simply place the negative in an empty tray and pour over it sufficient intensifier to fully cover it, and allow it to act until the surface of the film is all of an even color, rocking the tray gently to avoid unevenness and streaks. After the negative has taken on the required density pour the solution back into the bottle labeled "Intensifier for Use;" then wash the negative for about fifteen minutes and place in the rack to dry. Should the beginner desire to compound his own intensifying solutions, we refer him to Chapter V (Purple Tones On Collodion And Gelatin Glossy Papers), Volume II.
Reducing. Reducing is the treatment of strong, harsh, thick negatives in such a manner as to make them more transparent, thus giving them a better printing quality. Negatives that take hours to print from can be quickly reduced to the correct density for quick printing by use of the reducing powders. These powders, which can be purchased from any dealer, are very convenient for the beginner and are, therefore, recommended. The best time for reducing a negative is when it is taken from the fixing bath. If negatives that are dry are to be reduced they should be first placed in the fixing bath for a few minutes, then transferred to the reducer until reduced to the desired stage, and afterwards rinsed and washed for fifteen minutes and dried as usual.
Preparing The Solution. To prepare a reducing solution, take as much of the reducing powder as is called for in the instructions, and dissolve in the given amount of water. Label the bottle containing the solution "Reducing Stock Solution." With the negative carefully washed, place it in a tray containing a sufficient quantity of the reducer, and leave it in the solution until the density has been reduced to the required extent. This can be judged by lifting the negative out of the tray occasionally and holding it to the light. Keep the tray moving during the action of the reducer, to avoid uneven reduction, streaks, spots, etc. When reduced to the desired stage the plate should be at once rinsed, and then washed for 15 minutes in running water, and dried in the usual way. The reducing can be done in daylight, as the light has no effect upon the negative, and one is better enabled to judge the results. A negative that has been previously washed and dried can be placed into the reducing solution without again washing it. The prepared solution is usually good for only a short time, and should be discarded after use.
312. Note: As advanced instruction for reducing, intensifying and altering negatives is given in Volume II, the instruction given herein will suffice to prepare you for more advanced work.
Illustration No. 31Advantage of Reducing Thick Negatives. Half of Plate Reduced.
See Paragraph No. 304
Illustration No. 32Result of Intensifying Thin, Flat Negatives.
See Paragraph No. 306
Illustration No. 33Print from a Correctly Exposed and Developed Negative.
See Paragraph No. 315
Illustration No. 34Negative from which Illustration 33 was Printed.
See Paragraph No. 315