Cut the paper into suitable sizes, leaving a little extra margin at one end, and float it upon the hot gelatine solution as above; be careful in laying the paper upon the gelatine, that air bells are avoided; when the sheet is laid upon the surface, raise it rapidly, and throw it at once over a cylinder of cardboard or of wood, and at once commence to revolve this cylinder rapidly, first in one direction, and as the limit of the length of paper is reached, revolve it in the other, which motion will alternately bring first one end uppermost and then the other. By this means an even coating of gelatine upon the paper is secured, which is not possible when the paper is hung up by clips directly it is taken from the surface of the hot gelatine. The cylinder is kept revolving until the gelatine has set, when it may be hung up to dry upon clips, or laid face up, over a line upon a piece of cardboard; during the operation of revolving the cylinder, any air bells formed in the gelatine coating may be removed by blowing or pricking them.
This, to my mind, is a most elegant method of coating small sheets (up to thirty inches long) with a coat of gelatine, for which I willingly give the {137} Royal Engineers the credit, it having been demonstrated to me by Ex-sergeant Dalton, of that corps.
Paper coated in this manner, when dry, is ready for sensitizing; but if coated in the ordinary manner, it should, when dry, be coated a second time and hung up to dry in the opposite way that it was the first time.
Paper coated with gelatine solution as above, may be stocked, as the coating does not deteriorate with time; but the operator must be careful not to allow the solution of gelatine to get below 125° during coating, else the surface will be sticky. The temperature of the drying room must not exceed 70°, in fact, 60° will be best.
Paper so coated is sensitized by immersion for three minutes in
| Bichromate of Potash | 2 | ounces. |
| Water | 50 | ounces. |
In hot weather this solution must be kept cool with ice.
When the time of immersion has expired the paper is removed, and laid face down upon a sheet of glass free from scratches—which sheet of glass has been well polished with finely powdered talc (or French chalk)—now squeegee the back of the paper vigorously, to remove the superfluous solution and bring the surface of the paper into absolute contact with the glass plate. The sheet of glass is now placed in a rack, in the dark room, until the paper is quite dry, when it may be readily stripped off the glass, and is ready for printing the transfer. The operation of drying should be done in a current of air at a temperature of about 60°, and the paper must be quite dry before attempting to strip it from the glass.
The exposure under the negative is the same as described in the previous chapter.
When sufficiently exposed, the print is removed from the frame in the dark room, and at once immersed in cold water, where it is allowed to stay for five minutes, when it is withdrawn and laid upon a piece of plate glass, or a zinc plate, the face being uppermost; then the loose end of the paper (provision for which must be made in cutting the paper) is tucked under the plate, so as to hold the transfer in position in the subsequent operations.