OZOBROME A method of producing carbon pictures from bromide prints, patented by Thomas Manly, in 1905. Its advantage is that it makes the worker independent of daylight. Bromide enlargements can be made for producing carbon pictures, thus saving the trouble and expense of making enlarged negatives. Whether the carbon image is produced upon the bromide print or whether the pigment image is trans ferred to another support, the resulting picture is correct with regard to right and left. An ozobrome pigment plaster (paper coated with pigmented gelatine) is soaked in a bath of diluted ozobrome pigmenting solution, trans ferred to an acid bath for a few seconds, squeegeed to a wet bromide print and left for about twenty minutes for the insolubilising action to take place. The method of working is as follows : Place the bromide print in a dish of water, immerse the pigment plaster in the diluted ozobrome pigmenting solution until soft and limp (about one or two minutes), and then with draw the plaster and immerse it for ten to fifteen seconds in a bath of Chrome alum (pure) . 36 grs. 16.5 g.
Bisulphate of potass.
(cryst.) . . 12 55 Citric acid . . 5 Water . . . 5 oz. 1,000 ccs.
An immersion of, say, 20 seconds will produce a soft, delicate picture from a strong bromide print, and an immersion of, say, 7 to to seconds will give a strong, deeply-coloured picture from a weak and grey bromide print. For a good,
well gradated bromide print, an immersion of from 12 to 15 seconds would be sufficient. After removal from the acid bath, the soaked pigment plaster is brought into contact with the bromide print lying in the dish of water. The two papers (clinging together) are quickly with drawn, squeegeed together, and allowed to remain in contact for 15 to 20 seconds. One of two methods may then be selected to produce pigmented pictures. In the non-transfer method, the bromide print itself forms the support of the gelatine image. The adhering papers are plunged into water at about r6oฐ F. C.), the plaster backing is removed, and the development carried out as in the ordinary carbon process. In the transfer process the plaster and bromide print are separated in cold water, the pigment plaster carrying an impres sion of the image. The plaster is squeegeed to a soaked piece of transfer paper and left for to to 15 minutes, when the development is carried out in hot water in the usual way. The second method is preferable to the first one, as it yields u pure carbon picture with a choice of paper support, and leaves the bromide print, after redevelopment, available for further transfers.