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294 THE PHOTOGRAPHIC NEWS. [June 19, 1868. which may be done in several ways according to the size of the camera. A good form would consist of a strong table frame supported on four or more legs, according to the length. At one end of this the plan-board would be firmly fixed, so as to be at right angles to metal grooves fixed in the sides of the frame, in which the part carrying the camera would travel by means of metal runners. If necessary, the other end could be left open to admit the operator when focussing, the sides of the frame being held together by iron bracings at points between the part usually occupied by the camera and the board, the legs being cemented together near the bottom. The plan-board should be marked in one-inch squares, which, with the squares and lines marked on the focussing glass, will be a great aid in ascertaining that the image is perfectly square and of the proper size. A set of Holt- zappfel's engine-divided scales, on cardboard, will be found useful in measuring the reductions. A spirit level will be required for adjusting the camera. No other special apparatus will be required for the photo graphic part of the process. The following zincographic apparatus will be necessary for those who wish to lay down their own transfer's:—A lithographic press; inking table, constructed as a cupboard, to hold the roller's, inks, &c.; inking stones, one for transfer ink, the other for printing ink; lithographic rollers ; one or two palette knives for mixing the inks; zinc plates, one polished, others according to requirements ; graining sand ; mullers for graining the plates; a lump of snake stone and some snake slips; a scraper arrd eraser for correc tions ; old linen cloths for damping, &c.; litho printing ink; retransfer ink; turpentine; gum arabic; nutgalls; phosphoric, nitric, muriatic, and sulphuric acids; strong solution of potash ; stout demy paper, for offset sheets, &c.; plate paper and enamelled paper for printing ; thick bank post paper for transfers: all these may be obtained from Messrs. Hughes and Kimber, of West Harding Street, Fetter Lane, or other dealers in lithographic materials. I shall give a fuller description of such of these articles as require it when treating of the zincographic part of the process. Having now described the apparatus required, I will proceed to the details of manipulation. PREPARATION or the Negative. As I have observed before, in this process success mainly depends on the quality of the negative, and without perfect negatives perfect results cannot be obtained. It will often happen that copies are required of some subjects of which perfect negatives cannot be obtained. In this case the only thing to do is to obtain as good a result as the subject will permit. The manipulations are the same as those of the ordinary wet collodion process, with which I assume my readers are familiar. The first point that needs attention is the focusing. It is better to do this before fastening the drawing on the board. The first thing to do is to adjust the camera, so that the image of the centre of the board may coincide with the centre of the focusing screen, which, in a properly con structed camera, will occupy the position of the centre of the sensitive plate. Now compare the images of the squares. We will suppose it is required to produce a copy half the size of the original: to do this, the position of the camera must be altered till a square eight inches in the side exactly occupies the square of four inches in the side marked on the focusing screen. When this is the case, the surface of the board and that of the sensitive plate will be perfectly parallel. The drawing is now fastened on the board, and the sensitive plate got ready. The glass plate, being thoroughly cleaned in the usual way, is coated with bromo iodized collodion containing very little bromide (only just sufficient to secure cleanness in working is required; a good iodized collodion may sometimes be used with ad vantage when everything is in good order) ; it is then sensitized in a 35-grain bath of nitrate of silver, faintly acid with nitric acid. The exposure must not be pro longed, or there will be danger of deposit on the lines; it must be carried just far enough to produce as much intensity as possible on the ground of the negative, while the lines remain perfectly free from deposit. The developer is as follows :— Protosulphate of iron 1 ounce Glacial acetic acid ... 1 „ Alcohol ... } „ Water ... 1 pint I have found the addition of gelatine or glycerine, as recommended by Mr. Nelson Cherrill, advantageous in keeping the lines clear, and increasing the density. The development must not be carried too far. The plate is fixed in a 15-grain solution of cyanide of potassium, and examined by daylight. If the lines are perfectly clear, the re-intensi fication may be proceeded with ; but if the lines are not quite free from deposit, Mr. Osborne’s clearing process may be used with great advantage. The cyanide having been well washed off, the following solution is applied to the plate:— Iodide potassium 2 grains Iodine ... ... ... ... ... 1 grain Water ... ... ... ... ... 1 ounce It is allowed to act about a minute, and washed off; the plate is then covered with a weak solution of cyanide, the effect of which will be to clear the lines very much. If this treatment should not produce the desired effect, it will bo better to try another negative, giving less exposure, or not carrying the development so far. The plate is washed, and again covered with the iodine solution, which is washed off almost immediately ; and care must bo taken to wash the plate thoroughly before proceeding to the re-intensification. Re-intensifying Solutions. 11.—Pyrogallic acid 4 grains Citric acid ... ... ... ... 4 „ Acetic acid ... ... ... ... 15 minims Water ... ... ... ... ... 1 ounce 1.—Nitrate of silver 30 grains Water ... 1 ounce T wo or three applications of the re-intensifying solutions