the production of images in printing ink, a fatty acid or a resin has to be applied. The print, if in carbon, was subsequently washed with water containing a little hydrochloric acid, and a piece of paper coated with gelatine applied to its surface, attached to which the collodion film, with the image upon it, was removed from the glass. In some cases the sensitive fluid was applied direct to the glass, and when the picture had been produced by the application of carbon to the exposed film, a coating of collodion was applied, and the whole eventually transferred to gelatinized paper. This was the first process in which a collodion film was used for the purpose of transferring the carbon picture from a glass plate to paper.
In the following November,[1] M. Fargier brought before the French Society a process for which, in the September previous, a patent was obtained. It consisted of an ingenious combination of previously published discoveries. A plate of glass was coated with a mixture of gelatine, bichromate, and carbon, and, when dry, exposed under a negative. The exposed film was then coated with tough, plain collodion; and, after allowing the film to set, the whole was plunged into warm water. This dissolved the portion of gelatine which remained soluble, and detaching the film from the glass, removed the unaltered pigment and gelatine, leaving an image attached to the collodion film with perfect gradation of half-tone from white to black. The film was next attached to a sheet of gelatinized paper, collodion side uppermost. The results were exceedingly beautiful, far surpassing in delicacy and gradation anything which had previously been produced in carbon printing.
- ↑ “Photographic News,” vol. iv, p. 390.
