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.
Thin Slides. Thin slides are generally caused by under-development.
Warm Tones. Prolonged exposure and restrained developer give warm tones.
Varnishing The Binding. The binding of a lantern-slide may be protected by painting over with shellac varnish.
Warm Slides Before Mounting. Slides should be warmed slightly, so that they will be thoroughly dry before mounting and binding.
Slides From Flat Negatives. Plucky slides can be obtained from thin or flat negatives by using slow plates, slightly under-exposing, and using a diluted developer.
Sorting Negatives. Remember that a great deal of time is saved when making a large number of slides, by sorting your negatives into batches of approximately similar density.
Slides From Hard Negatives. Slides made from hard, contrasty negatives, should be slightly over-exposed and developed quickly.
Pin-Holes. Pin-holes can be touched out in lantern-slides with a sharp pointed pencil, holding the pencil in a vertical position, with a dotting action.
Making White Ink. White ink for writing on slides can be made by mixing artist's zinc-white with water. About GO grains of gum arabic should be added to every ounce.
Reducing. To reduce over-developed slides, take two ounces of 10% solution of Hypo and add 10 drops of saturated solution of Red Prussiate of Potash (Potassium Ferricyanide). Place the slide directly in this immediately after coming from the Hypo, and watch the reducing carefully. Remove as soon as reduced sufficiently, rinse, and return to the Hypo for five minutes.
Slide Over-Exposed. When a slide is overprinted, by the time the high-lights are sufficiently strong the shadows will have become too dense or clogged. If, on the other hand, the shadows have not attained sufficient density, when the high-lights have their proper strength, and the shadows appear veiled, rest assured that the slide has been over-exposed.
Wash Thoroughly. Lantern-slides must be thoroughly free from Hypo or trouble will arise.
Storing Slides. Lantern-slides should be stored in a warm, dry place; otherwise they are apt to absorb moisture.
Distinguishing Film Side. The emulsion on a lantern-slide plate being very thin and very glossy, it is sometimes hard for the beginner to distinguish the glass side from the film side. By breathing on both sides of the plate it will be no trouble to judge correctly. The glass side will become dulled by the moisture, but the film side will show no change.