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.
No Snap Or Contrast In Slide. This is almost a certain sign that it is over-printed or over-exposed. Be careful about this and treat the slide according to the exposure. If over-exposed, add more Bromide to the developer. It is better to have the slide a trifle under than over-exposed.
Slide Too Contrasty. Much under-exposure or an excessive amount of Bromide will cause contrasty slides.
Slides Weak And Gray. This is a certain sign that the slide was either under-developed or over-exposed, and that the slide, in development, was not treated according to the exposure. Aim for accurate exposure and if the plate shows signs of overexposure add a few drops of Bromide to the bath.
White Part Of Slide Not Clear. Again a sign that the slide was over-exposed and not treated according to the exposure, therefore a fogging of the whites is produced.
Overcoming Over-Exposure By Reduction. An overexposed but fully developed slide, or one over-developed, can often be made into a good slide by immersing it, after fixation, in a weak bath of Ferricyanide of Potassium, stopping the reduction when the desired clearness is gained.
Local Reduction. Slides that are too dense in parts can be locally reduced by the application of a weak solution of Ferricyanide of Potassium to the parts to be reduced. Many expert slide-makers prefer to over-develop their plates and then reduce down to the desired density by using a Ferricyanide bath. (For method of Reducing, see Volume II.)
Grain In Film. Under-exposure and prolonged development will frequently produce grain. If the lantern-slide has been made from a copy, the grain may have been caused by the grain in the original picture. Extremely slow drying of the lantern-slide will also cause grain. Drying too fast will sometimes cause grain. Be careful that the plates are thoroughly washed in clear water, and if the water is dirty see that each slide, before it is set up to dry, is swabbed with a piece of absorbent cotton which has been thoroughly saturated with clear water. Dry the slides in a well ventilated room, where there is plenty of air and not too much heat. Dry with a fan when possible, but do not have the fan too close to the negatives.
Unable To Produce A Brown Tone. Carefully follow the instructions and prepare the developer according to the formula given for this purpose; give the proper exposure, and you will have no trouble in overcoming this difficulty.
Difficulty In Properly Placing The Cover-Glass Over The Slide. Carefully examine the slide, holding it up and looking over the surface of the glass, and observe which way the slide and cover-glass curve. Then place the slide and cover-glass in contact, so that both curve in the same way. The remedies for difficulties encountered in the developing of ordinary dry plates can also be applied to the development of lantern-slides. For further information on Developing, see Vol. II.