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.
Negative Reducing Too Slowly. Plates or films which have been fixed in a bath containing alum, acid, or any hardening chemical, are apt to reduce slowly, and at times not at all. Plates which have been dried a long time will reduce slowly unless the film on the plate is thoroughly softened, and this is done by first placing in water for ten minutes and then transferring to the hypo bath for half an hour. It is also necessary at times to strengthen the reducing solution by adding reducing agent. If too much hypo bath was used the reducing agent would act slowly, as the hypo would overpower and weaken the reducing agent.
Negatives Reducing Too Quickly. If the reducing solution acts too quickly, it is because the reducing agent used is too strong. Remedy: Add more hypo solution.
Negatives Will Not Reduce. If the negatives will not reduce place in fresh water for one-half an hour, then into the regular fixing bath for another half-hour, and reduce with double strength reducing solution. Use twice the amount red prussiate solution to the regular amount of hypo.
Reducing Shadows Too Much. If the shadows in the negative are reducing too much you should use the persulphate of ammonia reducer. Only by careful manipulation, however, can you reduce the highlights alone with red prussiate reducer. Apply carefully to the parts of the negative which need reducing. Do not allow any of the reducing agent to touch the shadows.
Negatives Stained A Reddish - Yellow After Reducing. If the plate, or film, is stained a reddish-yellow after reducing it is because the negative was not perfectly fixed before reducing. It was not allowed to remain in the hypo long enough to remove all the silver from the plate. If the reducer is applied before the silver is entirely eliminated it will cause a stain which is almost impossible to remove. However, the clearing bath (formula for which is given in paragraph 270, Part I, Negative Reducing) will generally improve the color.
Negatives Streaked After Reducing. If the negatives have a streaky appearance after reducing, it is because they were allowed to remain in the reducing solution without agitating - rocking the tray - or if the plate is not thoroughly fixed before reducing it is apt to reduce in streaks. Remedy: Always fix plates, or film, ten minutes after the silver, or white, has disappeared, and carefully rock the tray while the plate is being reduced.
When applying the reducing solution locally, unless great care is exercised the reducing agent is liable to run on the plate and this would cause streaks. Remedy: When applying locally place the plate flat in a horizontal position, allowing the solution to remain on the plate for only an instant at a time, and rinse under the tap after every application, and before examining.
Negatives Yellow After Reducing. If the plate is yellow after reducing it may have been slightly yellow before reducing, and the reducing will make this yellow stain a trifle darker. If the reducing agent is too strong, or the hypo too weak, reducing is apt to stain the plate. Generally the alum clearing solution will remove this stain.
Removing Yellow Stain From Negatives After Reducing. If you find that the clearing bath will not act readily, add a little more alum and sulphuric acid. Sometimes, however, one may have added too much acid to properly balance the bath. In such a case the addition of more alum only to the bath already prepared, will at once start the plate to clearing. Care must be exercised when adding more alum or acid. Too much alum will pucker the film, and too much acid will reduce the plate. Therefore, add only a little alum at a time, and only a drop or so of acid. Use only chemically pure acid, and ground alum.
Surface Of The Plate Puckering After Going Through Clearing Solution. If the surface of the plate has a shriveled - up appearance, it is because the clearing solution contained too much alum, and the strong alum puckered the film. Very little can be done to remedy this. Sometimes soaking in a fairly strong solution of carbonate of soda, and then washing thoroughly, will bring the film back to its proper form.
Negatives Reducing In Clearing Solution. If the negative continues to reduce in the clearing solution, it is because the clearing bath contained too much sulphuric acid. When you first place a plate in the clearing solution allow it to remain for a moment only, and then rinse it under the tap before examining. If you find that the clearing bath is reducing the plate add more water before you place the negative back in the solution.