roasting jack. Such makeshifts, however, should only be resort ed to by the genius who finds himself in a corner, and, nothing daunted, is determined never to stick. We give in the follow ing diagrams the forms of two of the most frequently used. The working of the first will be readily under stood from the drawing ; that of the other we may describe as being made of hard wood, the long arms of thin hickory about 18x41 inch, around which is placed a broad rubber band. Being of such thin material the arms will spring out to suit almost all size plates within its capacity. The plate is held within grooves at the extreme end, or, what is better by small screws placed on the outer edge, the heads of which, holding the plate outside, allows the solution to flow uninterruptedly away under the motion. The diagram will explain how the motion is imparted, and it will also be seen that this form of whirler is very convenient for holding in the hand over the heat and at the same time whirled rapidly by the small handle at the upper end.
Preparations for plate is now ready for printing. To this end let the thick plate glass of the printing frame be seen to as being thoroughly clean, also the negative. Fre quently a moisture will collect on the glass of the negative. Frequently a moisture will collect on the glass of the negative, to obviate which let it be held over the gas stove for a few seconds.
As to the printing frame, it is scarcely necessary to describe it more than in a general way, that it is a square frame about four inches deep, in which is placed a piece of plate glass of from three quarters to an inch in thickness, of sufficient strength to withstand the pressure necessary to se cure complete contact between the negative and the metal plate. This pressure is got from screws, as will be seen in Figs. 38o and 381. The frame must be purchased anyway, and its con struction and working will be readily understood when practically examined.
Loading the Printing the sensitized metal plate and rest on the points of the fingers of the left hand, and place the negative over it so as the picture will fall exactly in the center ; or lay the negative in the printing frame, film side up, and lay the sensitized plate over it. Let this be done gently and without moving about, so as to save any risk of abraiding the film of the negative. Turn over and convey to the printing frame ; place over them one or two pieces of felt; put on the cover, and proceed to screw down. This must be done very carefully so as not to break the negative. The safest way is to bring a gentle pressure to bear upon the centre screw, and on the others radiating from the center, and lastly on the corners,repeating this gently, always beginning at the center and going over the others until close contact between the negative and the plate is obtained.
The plate is now ready for exposure, with a view to print-k.
ing ; and here judgment and experience. the outcome of experiment, must be the best guide of the student. There are two elements on:which he will have to bring his judgment to bear: first, the density of the negative, and, secondly, the intensity of the light. It may take anywhere from one to ten minutes. If a bright sun is out, and the negative of medium density, one minute may be ample, varying with a cloudy sky or a hazy atmosphere. A few practical experiments and the waste of a few plates will afford better lessons than any written words can convey, and knowledge will come as the reward of patient perseverance.
Development. — Having given what is deemed to be a suf ficient exposure, remove the printing frame into the dark room, unscrew and take out the plate, and place in a dish of slightly warm water, and rock for a few minutes. At this point it may be examined as to whether a correct exposure has been given. If so, the enameling solution will be found a little tough when raised by the finger nail at any of the margins. If the time given has been too short, it will have washed away under the action of the water, especially when placed under the tap to wash out, which should now be done. If correctly timed it will stand considerable washing without injury. The effect will have been to wash out those parts of the solution which have been protected from the light by the denser portions of the negatives, and the half-tones in varying proportions.
Drying after been sufficiently washed, the drying may be accom plished by being set aside and allowed to dry spontaneously, or, as the manner of some is, to to reach the more expeditiously, the plate may be flowed over with alcohol, and, held in tongs or pincers, a flame set to it, when it will be dried at once and be ready for the next oper ation, which is the burning in.
Burning operation is best performed over a small gas-stove, and requires a pair of large pincers, about twelve inches long, with broad point that will hold a good grip of the plate by the margin of the picture. It must be kept moving over the flame to and fro, so as to distribute the heat gradually and regularly over all the plate. In a few minutes it will be seen to change color and the picture to develop out more plainly. At this point it is safer to lay aside for a few minutes to partially cool, as a great heat too quickly brought to bear upon the enamel may cause it to crack ; meanwhile, other plates may be proceeded with and brought to the same stage. The burning should be continued until it assumes a rich deep brown, when it should be laid aside to cool gradually, when it is ready for the etching.