With regard to the correct time the paper should be allowed to remain upon this solution, this depends both upon the strength of the bath and the temperature of the solution and of the atmosphere. Further, different brands of paper often require different lengths of time for sensi tizing, and it is also influenced by the character of the negative and the effect to be produced in the resulting print. Many operators sensitize their paper of different degrees of strength for the various negatives from which they have to print; for instance, for weak negatives, a paper sensi tized strongly. The usual time, however, may be said to vary from 4o to 70 seconds in the sum mer, and from 6o to foo seconds in the winter.
The correct time for sensitizing, as has already been stated, is dependent upon so many considerations that some amount of thought and experience is required by the operator to get the best class of results.
After the sheet has been allowed to remain for the required time upon the solution, it is slowly raised by two corners and drawn slowly over the edge of the dish, or preferably over a glass rod attached to one side of the dish. In this manner the superfluous solution is removed from the surface of the paper. Some operators prefer to do this by laying a sheet on a piece of bibulous paper, but unless this be perfectly pure and free from antichlor, the method is rather risky.
The sheet is next fixed at one corner to a clip, and at the opposite or lowest corner a piece of white blotting paper is affixed to absorb the moisture.
The drying of the paper is an important point. It should not be done spontaneously, as the silver solution will then sink into the paper, and the brilliancy of the prints is lost.
The sheet is first allowed to drain and become partially dry, and then finished thoroughly by heat in a drying cupboard fitted with a row of gas jets or a stove. In this the top of the sheet is attached to two clips. If it be found that the paper curls up in drying, pieces of wood the
same length as the paper with a clip at each end are fixed to the lower edge of the paper to keep it straight.
The heat for drying should be diffused and sufficient to quickly dry the sensitized paper. The following are the failures likely to be met with in sensitizing albumen paper, and the causes.
The paper repels the silver solution. It is too dry.
White spots are produced if bubbles of air are allowed to remain beneath the paper when floating. The corners should be lifted up as soon as paper has settled down and the air-bells removed.
Small drops of the silver solution termed "tear drops" adhere to the sheet when hung up to dry. They should be blotted off immediately, and are caused by the paper being too dry.
The paper discolors quickly if over-sensitized.
A dull and sunken-in appearance of the image may also be caused by over-sensitizing.
Bronzing of the dark shadows is also sometimes the result of over-sensitizing.
Poor, weak prints are usually produced by too short sensitizing. Greasiness of the paper is also produced either by insufficient sensitizing or by the solution being very cold. Unpleasant foxy-reddish tones of the prints are often caused by too short floating on the sensitizing bath.
The curling of the paper on the solution is caused by the paper being either too dry or the albumen film being too tough. Breath on the back of the paper until it lies down flat again.
Stains are sure to appear if the sheet is allowed to come in contact with any unclean substance.
Dark stains on the back are produced by the silver solution running over the back.
Small dark spots or specks are caused by small metallic pieces of dust imbedded in the paper. They can sometimes be removed with the sharp point of a knife, Inequality in the prints is due to uneven sensitizing.