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.
Definition Of A Negative. The action that is taking place on the plate during development is as follows: The light that passes through the lens affects the plate in proportion to the strength of the rays from the object; consequently, the rays of light from the shadow parts of the object will have less action on the plate than the rays of light from the lighter parts. During development, the parts of the plate most affected by the light appear first, and will grow darker as development proceeds, while the parts affected by the shadow rays will show but slight discoloration on the plate. This is why the plate is called a negative, because it gives the lights and shadows in reverse order to what is actually seen in the object.
Judging Development. Carefully remove the plate - handling it by the edges only - from the tray and hold it up to the ruby light, looking through it. If the highest points of light, or more clearly speaking, the blackest parts of the image, are extremely dense, so that you can scarcely see through them, then the development has been carried far enough. When those parts of the sensitive film on the plate - emulsion-which have been affected most by the light have been reduced completely to metallic silver, through the process of development, it is impossible to carry them any further. Continued development will simply reduce the more delicate tones, making them as dense as the highest points of light, thus causing what is usually termed a spreading of light, and when a print is made from such a negative the high-lights are hard and chalky, instead of being soft and mellow.
Fixing. After development, the plate should be thoroughly rinsed in clear water; then place it in the hypo fixing bath, film side up, where it should remain until the unexposed and undeveloped silver salts have been removed. In other words, all the white that appears on the plate, as seen when looking at the back of it, must be cleared away. A negative should not be examined, except by ruby light, until it is thoroughly fixed. This may require ten minutes, or longer, and in order to assure thorough fixing the negative should remain in this bath double the length of time necessary to remove the white effect, or unexposed silver salts. After the plate is fixed, place it in another tray for washing (if you have no washing box) and allow the water from the faucet to run into the tray gently, so as not to strike the face of the negative. An ordinary pail or basin may be used, if a tray or washing-box is not available. Washing should be continued for at least twenty minutes, and then the negative should be placed on a rack or stood up against the wall to dry.
Drying. Negatives should be dried in a well ventilated room. If the room is too warm, the film is apt to become soft and the negative will be ruined. Never dry the negative in the sun or near the stove.
127. This instruction is only a primary one, dealing with prepared chemicals, and has been made as simple as possible, giving no reasons, as these features will be fully explained in succeeding instruction.
128. Proof prints should be made of your experiments of this instruction, and all data pertaining to the results secured or failures met with noted on the back of each individual proof. Each of these should then be numbered and dated in the order made, and filed for future reference in your letter file or proof book.
Defective Negatives and Their Cause.
129. Illustration No. 21 shows a case of blistering, caused by a difference in the temperature between the developer and the wash water. Blistering is also caused by the wash water, as it comes from the faucet, containing a considerable amount of air, which being forced under the film, raised it on the spots shown. The solutions and wash waters must always be kept at a uniform temperature, and the water coming from a faucet must not be allowed to drive on the plate. Should the water contain a considerable amount of air, as is the case where water is pumped into the mains, or sometimes when breaks in the water mains have been repaired and the water again turned on, forcing air into the pipes, this air or gas may affect the film. Under such conditions it would be far better to wash the plates in a tray, changing the water at least ten times during a period of one hour. The water used should have been drawn from the faucet and allowed to stand for five minutes before placing it in contact with the plate.
Illustration No. 22 Showing the Result of Fogging the Plate See Paragraph No. 130.
Illustration No. 23 Showing the Results of Uneven Development See Paragraph No. 131.
130. Illustration 22 shows the result of fog when the plate holder is not properly inserted in the camera. It is absolutely essential that the holder be pushed in far enough so that the rib or groove on the camera fits snugly into the groove or rib of the plate holder. If they do not fit properly, fog will invariably be the result. This fog occurs in different forms, but the one illustrated herewith is quite common. Frequently when the plate holder is not properly inserted in the back of the camera the top and bottom of the plate will also be fogged. Improperly inserting the slide in the holder will cause a similar fog. The slide must never be inserted one corner first; always push it in straight, i. e., the end of the slide must enter the slot evenly. (See Illustration No. 11).
131. Illustration 23 contains numerous defects, but the one which comes to our attention most strongly is the uneven development shown by the large, light streaks, which were caused by flowing the developer over only a portion of the plate in place of covering it entirely. It is absolutely necessary that the developer be flowed evenly and uniformally over the whole surface of the plate at once, for if this is not done, streaks and spots will result.