Another method is to expose as usual for the landscape, develop, and clear; then, without fixing, place again on the easel, and with the yellow cap on the lens, focus the clouds from the cloud negative and adjust till in correct position, and then cover up the landscape with a mask cut from ruby paper, and expose for the clouds. The exposure for clouds should be very short, so as not to make them too dark and prominent; practically about one-fourth of the exposure required for the view will be correct for the clouds. Trees, church steeples, and other objects projecting into the sky may be practically disregarded, as these will print over the sky and give a more realistic effect. To prevent too sharp a line of demarcation, the mask, or a sheet of cardboard cut roughly to shape, may be gently moved up and down near the sen-sitive surface to shade the landscape into the sky. In enlarging, as in every other photographic process where success depends upon a variable quantity as personal skill, care, and judgment, failures are unfortunately too often met with. We shall there-fore proceed to consider these in the order of the several operations.
The enlargement is out offocus, especially at the edges. This fault may be due to non-coincidence of the plane of the sensitive surface with that of the focussing paper or ground glass. This may be remedied by focussing as usual, then placing a piece of orange glass over the lens, fixing the sensitive surface in position, and examining the focus; -and, if it appear sharp, exposing and examining the developed print. It may also be caused by the sensitive paper buckling or not lying quite flat, and also by using too large an aperture of the lens. The former may be prevented by straining the paper very tightly, and the latter obviously by the insertion of a diaphragm. It may also be caused by using too large a flame surface as illuminant. Other failures are treated of under Bromide Paper (q.v.).
Sensitising Canvas for Enlargements.
A writer in the Photographische Correspondenz gives the fol-lowing methods of sensitising canvas for enlarging direct. The canvas must first be well washed with a solution composed of
Liquid ammonia-88o ......... 10 parts.
Alcohol (methylated) ...... ... 40 ..