Finger-marks on the back of the paper, although they always show very plainly whilst the print is wet, usually disappear entirely when it is dry.
If paper has been fumed, and the action of the am monia has not been even, unevenness of tone is sure to result.
The portions of the Print which, ought to be white are yellow.
This is a very common and most annoying defect. A great portion of the beauty of a photographic print depends on the pureness of the whites ; and this is especially true in the case of vignettes.
There are several causes of the defect. The first which we will take lies in the paper itself. If ready sensitised paper be kept too long, or be kept for a comparatively short time, in a damp place, or in a place where it is exposed to gas fumes, it will turn first yellow then brown. It is unreasonable to expect from such paper prints which will have pure whites. Exposure to the air will also cause the change of colour. The paper therefore should be kept tightly rolled up ; it will then keep almost in definitely. If it be found necessary to keep for any length of time paper which has been unrolled and cut up, it is best to put it under pressure ; it may be placed under a flat board with a weight over it, or it may be placed in a printing frame, the back of which will afford the neces sary pressure. In this latter case a sheet of ordinary paper should be placed between the sensitised paper and the back of the frame ; otherwise there will appear in time a dark line on the paper corresponding with the division between the two halves of the back.
Printed paper, such as newspaper, etc., should on uo account be placed in contact with sensitised paper, other wise the printing will become visible on the sensitive surface.
It has already been said that paper sensitised as re quired will not keep, except under certain conditions, for more than about twenty-four hours. It sometimes happens that it is necessary to leave a negative in the frame for a longer time than this before a single proof can be got from it. This may be the case with very dense negatives, and when the weather is very dull. In
this case there should be placed between the sensitive paper and the back of the frame a piece of blotting-paper which has been soaked in a saturated solution of washing soda, and has been dried.
The yellowness and brownness which we have de scribed is unobjectionable compared with that which we are about to describe, inasmuch as it is evident on the paper before this is even put in the frame, so that we know what to expect. Moreover, it is much reduced in the toning and fixing baths. In fact, a piece of paper which is quite perceptibly brown before it is put in the frame may give a perfect print. There is, however, a defect which is caused in the toning or fixing-bath, and which is, so far as we know, incurable, and moreover is accompanied by a general degradation of tone which makes the print totally useless. It is often accompanied by a curious metallic lustre on the surface of the print. This is to be distinguished from bronzing (to be after wards described) by the fact that, whereas bronzing appears only in the deeper shadows of the print, this metallic lustre covers the whole surface, or, at any rate, the whole of that portion of the print which is affected with the fault, irrespective of lights and shadows.
There are several parts of the process at which this defect may make its appearance. The first is when the print is first being washed before toning ; and this is, we believe, the most common. If the prints are allowed to remain for any length of time in the first washing water, which contains a considerable quantity of nitrate of silver, they will almost certainly be turned yellow in the high lights. This is still more certain to take place if they be allowed to stick together, and yellowness will give place to brownness if too much light get access to the washing water at this stage.
The prints should be kept in as constant motion as possible in the first and second waters, and should be as quickly as possible transferred from the first to the second, and from the second to the third waters.