W.K. Burton, K. Ogawa, Printing Processes

Photo-mechanical Printing In Japan.

At the same association, a fortnight ago, a paper by Mr. W. K. Burton, of Tokio, was read upon the above subject, and in it he gave a description of the works and methods of Mr. K. Ogawa, who was for some years the first and only photo-mechanical worker in Japan, with the exception that in the government military map department photo-lithographic work had been previously turned out. In his collotype work, Mr. Ogawa first strips the film of the negative by thickly coating the film with collodion, allowing it to dry, and then placing the plate in a weak solution of hydrofluoric acid. The film floats off, is turned over, and transferred to another glass plate which has previously been coated with gelatine to secure adhesion. Plate glass is always used, because of the great pressure the image has to endure in the printing frame. He sticks to no measured proportions of chemicals, but works by rule of thumb, yet with great certainty in results, because of long experience. When the hydrofluoric acid solution is too strong, the gelatine film will expand, or even wrinkle. The support for the chromated film is plate glass about half an inch thick, the edges and corners rounded by grinding. Collotype work is difficult in Japan, because of the extreme ranges of temperature in summer and winter, consequently the sensitive solution has to be varied to suit; the hotter the weather, the harder is the gelatine used; Nelson's opaque gelatine being used in cold weather, Coignet's "Gold Medal" at warmer temperatures, and isinglass in the hot weather; if the weather be extremely hot, even chrome alum is added. The quantity of colloid used is about 6 or 7 per cent, of the solution. The bichromates used are those of potassium and ammonium, in equal parts, forming 1 1/2 per cent, of the total solution in warm weather; in cold weather, more. The plates are dried in a cupboard, at a temperature of about, at a guess, 100 degrees Fahr.; they are dry in about two hours. After printing, the plates are sunned from the back for a short time, but longer for negatives with strong contrasts ; the plates are then washed in running water for about half an hour when the weather is warm, and for a much longer time when it is cold. The inking is done by hand, with two rollers; the first, a German roller, covered with leather; the next, a composition roller, with a thinner ink. With the highest class work an expensive Japanese paper is used, and but thirty impressions per hour can be pulled, and a plate yields about three hundred impressions. With high-surfaced European paper, fifty prints per hour are pulled, and the average life of a plate is about five hundred copies.

Recently Mr. Ogawa has worked chromo-collotype, which in his case is merely a mechanical method of coloring collotypes. "First," says Mr. Burton, "an ordinary collotype is made, and this is handed to an artist, who colors it, using whatever may be the fewest pigments that he considers necessary to produce the effect that he aims at. An average number is about eight, but sometimes as many as twelve are used. The single copy having been colored, a number of copies are taken corresponding to the number of pigments that have been used, and each of these is colored by the same artist with some one pigment, in the parts corresponding with those to which the same pigment was used in coloring the first collotype. These pigments are all of the nature of transfer ink, and a transfer is made from each of them to a lithographic stone. The transfers having been made, the collotypes are passed over the stones, each imprinted with one particular tint only, the number amounting to anything up to twelve. Perfect register is kept by two needles fixed in holes drilled in the stones, and passing through diagonally opposite corners of the paper."

Mr. Ogawa's photo-engraving works contain collotype machines worked by hand; he also has machines driven by steam for photoengraving work. He uses the Meisenbach process, and obtains grain by the employment of the diamond-cut screens made by Levy. He finds a distance of one-fifth of an inch, including the thickness of the cover-glass of the screen, to be about the best distance for average work between the screen and the plate; he most commonly uses a diaphragm of about i inch square, with a lens of 13 inches focal length; the less the contrast in the original, the greater should be the distance between the screen and the plate. The greater the distance between the lens and the plate, the larger should be the diaphragm. The chemical process used is one which has been sold in Europe and America as a secret one, which had been bought by Mr. Ogawa, so Mr. Burton asked him no questions in relation thereto, and described alone what he saw, from which it appears to be the fish-glue process. Ogawa's re-etching is done by applying the etching fluid with a fine hair pencil to those parts of the plate which have to be deepened. Plates are made for the trade by Mr. Ogawa at a rate corresponding to about 6d. per square inch. He turns out prints of about cabinet size at the rate of more than two hundred for a penny, if he gets a large enough order and the paper is supplied to him; in such cases, however, six different pictures are etched upon one plate, or six small plates are fixed to the bed of the machine.

In his paper Mr. Burton put forth the theory that, when using a cross-line screen, each dot produced is a diffraction image of the diaphragm.

Source: Anthony's Photographic Bulletin, Volume XXVI, 1895, pages 85-7.

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