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.
Collodionizing Or Coating The Plate. Assuming that the collodion has been prepared properly and has had an opportunity to ripen, that the silver bath has been made up according to instructions, and that the plates have been washed and dried ready for flowing on the collodion, you first take a plate from the rack, examine it and see which is the concave and which the convex side. This you can judge by placing the plate in such a manner that you can sight along its edge. The side which curves upward is the concave, and this is the side which should be coated. Catch the plate, by the lower left-hand corner, between the first and second fingers of your left hand, allowing the extreme corner to rest against the thumb. In this way you will have a firm hold of the plate and can tip it to any angle and in any manner you desire.
906. Another method is to place the plate on the tips of the fingers and thumb, separating the fingers slightly so the plate will be well balanced on the hand. Next, carefully dust the plate with a camel's-hair brush; then with your right hand take up your collodion bottle and pour a small pool of collodion on the center of the upper part of the plate. Tip the plate a trifle, flowing the collodion to the top right-hand corner, then to the top left-hand corner, next to the bottom left-hand corner, and finally to the bottom right-hand corner. The excess collodion should then be drained carefully back into the bottle. As soon as the plate has ceased to drip, replace the stopper in the collodion bottle. The collodion bottle must always be kept tightly stoppered when not in use, as the ether in the collodion will evaporate rapidly if left uncorked and the collodion would soon become thick and worthless.
907. When flowing the plate with collodion, exercise care that you have a clean sweep of the collodion over the entire plate. Should any portions receive a double coating, waves and streaks would be caused in the negative. Beginners are liable to permit the collodion to run over the back of the plate. With a little practice, however, working carefully and not using too much of the collodion, you will very soon be able to coat a plate properly.
908. In cold weather you will find that the collodion will set much slower than in the summer or warm weather. When there is an even dullness over the entire surface of the plate, which usually requires but half a minute, you can be certain that the coating is set and the plate is ready for the silver sensitizing bath. If you are at all in doubt, gently touch the corner of the plate, from which the collodion was drained, with the tip of the finger. If it shows signs of tackiness it is properly set. This test is usually unnecessary, as you will soon be able to judge by the appearance of the collodion on the surface.
Placing The Plate In The Silver Bath. All the previous operations may have been performed while the dark-room door was open, using plenty of light. At this stage, however (placing the plate in the silver bath), it is advisable to close the dark-room door, for while the plate is not sensitive to light until after it has entered the silver bath, yet, unless the location of the silver bath is sufficiently far from the door, the light might affect the quality of the plate; therefore, to insure safety close the door while immersing the plate. Place the plate firmly on the tips of the dipper and gently lower it with one continuous sweep into the silver bath. If you were to immerse a part of the plate and then stop for only part of a second before continuing the immersion, the plate would be liable to bear a line or mark across it at that place.
910. After the plate is fully immersed, it is advisable to raise and lower it a few times in the solution. This enables the solution to penetrate the film more readily, also removes the ether from the surface, and the action of the sensitizer becomes even. The plate should remain in this bath for about six minutes. The exact time, however, is governed by the temperature and the nature of the sensitizer employed. Usually, the higher the temperature the shorter the duration of the plate in the bath; therefore, in summer months, or in hot climates, two-thirds of the time required for winter months or cold climates will be necessary.
911. The single iodized collodion requires less time for immersion than where the collodion has been bromo-iodized, the latter of which is the method recommended herein. In the latter case it will generally require five to six minutes, while in the former, three minutes will be sufficient. The proper immersion can be judged from the appearance of the plate. If it appears at all wavy or oily on the surface, the plate has not been sufficiently immersed and must remain until this appearance takes place. Of course, the plate must be examined by the yellow light and not by daylight.