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.
Lens. Attention must be given to the lens during frosty weather. See that it does not scum over by the condensing of moisture in the air. This will occur on very cold days and when first taking the camera from the case. After the lens has been exposed for a short time so that it has the same temperature as the air, it will clear up. In order to avoid reflections from the snow into the lens, you can make a cone of black pasteboard and fit it around the underside of the lens tube, or holding the slide of the plate holder or any opaque substance under the lens (not too close to cut off any of the view) will prevent reflections. Reflections will not always occur, much depending upon the angle of light of the view. The reflection can, of course, be detected upon the ground-glass when focusing, and should it appear, it can be overcome by applying the above methods.
Developing. To develop snow scenes use the ordinary developing formula, diluting one-third with water, being careful of the temperature. Remember that the best chemical action takes place at 65° Fahr. Develop for softness, but carry the development a trifle farther than you would ordinarily, thereby producing a little more density. In this way pure white snow is secured. Never undertake to develop the negatives when they are chilled and cold, as they will develop flat and even worse than a greatly over-timed exposure.
676. If the ground is covered with snow when preparing architectural or landscape lessons, you will need to apply the rules governing the necessary exposure given in this lesson, and time accordingly. It is advisable for your first experience with snow photography, that you make at least two exposures of the same scene. The results in developing the first will enable you to judge how to develop the second. Proof prints should be made from both plates, on the back of which should be noted all data pertaining to the producing of the results. These prints should be dated and filed in the proof file, for future reference.