Further research has been done on the gelatin qualities and high image densities of older microfilms. This research has revealed adjustments that should be made to the dilution of SilverLock during application to ensure adequate drying with thicker emulsions. However, if they are in image areas, the consumer must weigh the disadvantage of possible additional degradation of the original or copies against the advantage of arresting further degradation. Red spots compromise the usefulness of film whether it is a service copy or a master copy. Yes, service copies can be replaced, but the low cost of treating them with SilverLock , compared with the cost of replacing them, makes protecting all silver film a worthwhile investment.
Quality control begins with proper solution preparation.
If the polysulfide concentrate is made correctly, diluted to recommended working strength, mixed immediately prior to use, and kept from prolonged exposure to air, one should encounter no problems. There are a number of tests that will help predict how polysulfide treated film will stand up against oxidants in long-term storage. Of these, the hydrogen peroxide immersion test is the easiest and most convenient. This test is ideal in a production or small lab environment, because test samples can be run with film stock and evaluated as often as desired over the course of the run. Correctly treated film will not lose more than 0.05 visual density during the procedure and will not show any discoloration.