Prints made by exposure to light of paper in a damp state, or made on dry paper and after wards damped, will, if developed within an hour of such exposure, give the maximum of vigor, by delaying the development for some hours, the prints in the meantime being stored in a drawer wooden box, or other suitable receptacle, so that they will retain most of their moisture, then, on development, an increase of half-tone and increased warmth of color will b5 obtained. The modifications in the results to be secured in this way can be only roughly indicated ; the ex perience of the printer will very soon prevent mistakes.
But should it be necessary to delay development of prints for one or two days, they must be dried (not scorched) before a fire soon after they are removed from the frames, and then stored in a calcium tube until wanted for development.
As during printing operations no necessity exists for keeping paper dry, it is very advis able on account of the ease of manipulation, to employ drawers, or flat wooden or paper boxes, one to hold unexposed paper and another to receive exposed prints. The hinged paper boxes made for holding music answer very well for the smaller sizes. This method of working from non-metallic boxes also avoids the risk of spots due to metallic dust, which is always produced during the opening and closing of a calcium tube of tin or zinc.
Exposure to is effected in a printing-frame in the usual manner. When ex posed to light behind a negative, the lemon-color of the paper receives an image of a greyish tone. Some negatives, however, present such strong contrasts that the deep shadows on • the print are carried beyond the gray stage and become of an orange-yellow ; this state of the image is usually termed " solarization." The exposure is somewhat less than that required with the old process—perhaps about one-third less. The progress of the printing is observed by opening the frame in the usual man ner, but care should be taken to prevent undue access of strong light. As a general rule all details observable on the exposed print are developable, and the converse. of this is also pretty generally true, namely, that no details are developable which are not also visible before develop ment. But here it should be observed that the action of light on skies is not often clearly seen unless the rebate of the negative has been previously rendered opaque by painting with opaque varnish, so that the tint of the sky may be compared with the original color of the paper which is preserved by the opacity of the rebate." It is important to remember that if paper be exposed
in a damp state the visibility of the image is less than if exposed in a dry state ; the image is weaker in appearance and less of the detail in the high lights is seen. On this account beginners will find it easier to expose dry, and damp the prints afterwards. This paper is undoubtedly easier to expose correctly than paper made for the former processes, and no one should experi ence any difficulty after a small amount of practice has been gone through.
developing agents are numerous, and a great variety of formula is possible. The best results are, however, obtained with mixtures of oxalates and bi-phosphates. The following is a good formula Oxalate of potash 3o grains Bi-phosphate of potash.. 3o grains Dissolved and made up with water to i ounce.
Platinum salt 3o grains Water r ounce For use add one part of B to three parts of A, although a great many variations may be made in the proportions to which these two solutions are mixed to form the developer, and by these variations different effects are produced.
The mixed developer keeps in good condition for some hours after mixing, but it afterward slowly deteriorates, and in order to secure due economy in the use of the developer, it is import ant to mix no more at a time than is sufficient for the prints to be developed. In developing a very large batch, perhaps the best way is to mix the whole quantity necessary, but to put into the developing-dish only sufficient to render the floating of the prints an easy matter, and then to add the remainder by degrees, as may be found necessary.
In order to develop, pour sufficient of the developer into a porcelain tray to well cover the bottom, and then float the print, with its printed surface downwards, upon the solution; after the lapse of two or three seconds it may be lifted from the solution and held in the hand. A few seconds after the print has thus been removed from the developer, it should be again simi larly floated and raised; and these operations may require to be repeated, but this will depend on the strength of the print or subject.