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.
Securing Proper Illumination On Negative Or Transparency To Be Enlarged. Follow closely the instructions given in regard to using a reflector for daylight. Adjust this properly and this difficulty will be readily overcome.
Judging Proper Illumination When Enlarging From Negative Or Transparency By Artificial Light. Be careful to place the artificial light far enough away from the ground-glass to illuminate it evenly all over. If a reflector or a white lined box is used, and care is taken to have the light far enough away from the ground-glass, an even illumination will be produced. If either condensers, the Folmer and Schwing enlarging apparatus, or the home-made enlarging camera are used, then by means of the number of ground-glasses employed you have absolute control over the illumination and will experience no trouble.
Obtaining A Sharp Transparency. When making a small transparency it is absolutely necessary that the plate be in perfect contact with the negative. By using a printing-frame, with good stiff springs giving plenty of pressure, this is very easily accomplished. Usually this difficulty presents itself more frequently where transparencies are made from film negatives, yet the film can be brought into absolute contact by backing, and having sufficiently strong springs in the back of your printing-frame. If these springs are rather weak, bend them back a trifle and they will give better pressure.
Overcoming Distortion. Be careful to place the camera and negative or transparency in an absolutely perpendicular position-the negative or transparency parallel with the camera-the distortion will then be overcome.
Producing A Sharp Image When Enlarging From A Small Transparency. Focus carefully with the lens wide open. Get the image just as sharp as possible on the ground-glass, and use a stop sufficiently small to sharpen the entire image.
Proper Exposure. This, like making regular exposures, requires practice, and it is necessary that the results be closely observed. Keep a memorandum of the conditions of light, strength of negative, and also exposures given. If, upon developing the negatives, they prove to be under or over-exposed, estimate accordingly the next time an exposure is made, whether it be a transparency by contact or a transparency by enlargement.
Transparency Plate Too Dense. This is either caused by over-exposure and over-development, or even by proper exposure and over-development. With a little practice this difficulty will be readily overcome. Should the plate be too dense reduce it with Red Prussiate Reducer, (See Vol. II).