PHOTOGRAPHIC PRINTING 565 



with perfect adherence to the paper. All these are found in gelatine, to which any 

 colouring-matter may be added. The ink must be kept warm, the heat and strength 

 being such as to ensure its setting in a reasonable time ; the mould should be slightly 

 moistened with oil to prevent the ink adhering to it. 



After remaining in the box for about a minute the paper is removed, taking with it 

 the mass of gelatine, which at this stage forms a picture in relief (hence the name of 

 this process, relief-printing'), but as it dries, this peculiarity gradually disappears, and 

 when it is quite dry not a trace of it is left. One operator may work several of these 

 presses at the same time, and by so doing he may produce from 150 to 200 prints per 

 hour. The print is fixed by immersing it for a short time in a solution of alum, which 

 renders it impervious to moisture and improves its mechanical condition. 



Mr. Walter Bentley Woodbury obtained two patents for modified forms of his pro- 

 cess in 1870 and in 1872, for sundry improvements in the ' Woodbury Type;' his 

 latest process being the following one, quoted from the Specification of his process, dated 

 December 4, 1872: 



' In place of using a thin film of collodion (as is generally used in the process called 

 '"Woodbury type') to hold the gelatine of the relief, I proceed as follows : I first rub 

 over a sheet of plate-glass with French chalk or ox gall, and then coat with the bi- 

 chromatised gelatine solution as now used. When this is dried and ready for use, I 

 expose the side that was next to the glass for a few seconds to daylight before exposing 

 it under the negative. This has the effect of causing a thin film of the gelatine to 

 become insoluble, which after subsequent exposure under the negative will not wash 

 away, but form a support for the photographic image afterwards impressed, thus doing 

 away with the expense and trouble of the double coatings as now practised. When 

 the gelatine relief is dried in the ordinary way I take a thin sheet of tin foil (same 

 size as the gelatine relief), and attach it by gum or other adhesive substance around 

 the edges to the gelatine relief. I now lay on the back of this a stout sheet of plate- 

 paper, and pass the whole through an ordinary rolling press ; the tin foil is by this 

 means impressed into all the details of the relief, but in that state it would be useless 

 to print from. I then proceed as follows : A shallow metal box is filled with a com- 

 position of shellac and asphalt which on warming becomes soft, but hardens on cool- 

 ing ; this box is placed on a hot plate until the composition it contains softens ; it is 

 then placed on the lower plate of the ordinary Woodbury printing-press, the foil and 

 relief laid on it, the press closed and the pressure applied by the under screw. When 

 the composition has hardened the tin foil adheres to it, and I remove the gelatine relief 

 from the foil, and use the foil-backed mould to print from. In place of fixing the 

 proofs by alum or other substance of a like nature I varnish the proofs with an ordi- 

 nary varnish composed of shellac and alcohol, which gives the print the effect of a 

 photograph on albumenised paper, at the same time protecting the surface from mois- 

 ture. I also sometimes use the composition above named without the foil as a 

 printing-mould direct, and when sufficient numbers have been printed the box holding 

 the composition is again heated, and can be used over and over again. The third part 

 of my invention consists in an improved method of printing Woodbury type by 

 machinery. This I accomplish as follows : Out of a solid block of iron I have turned 

 a cylindrical hole in which is made to fit very Icosely a cylinder of soft metal, having 

 a taper or conical hole through it lengthwise. Between the interior of the steel block 

 and the soft metal cylinder I insert the gelatine reliefs, then by means of a taper or 

 wedge-shaped spindle (roughened) I drive by hammering or by pressure the soft metal 

 against the iron cylinder, thus impressing the relief on the outside of the metal cylin- 

 der, the taper spindle at the same time forming a shaft for the cylinder to be used in 

 the process of printing. I then mount this roller bearing the relief in vertical slots 

 in a frame having a bed of plate-glass on which the paper rests, the roller resting on 

 the glass by its own weight and being dragged round by the paper itself, or in place 

 of the glass plate I allow the soft metal to lie on another fixed or moveable roller of 

 metal or glass. The latter may be hollow so as to reduce its temperature in hot 

 weather by a stream of cold water running through it.' 



Mr. Joseph Wilson Swan, of Newcastle, was a very zealous worker. He com- 

 bined with the bichromated gelatine carbon or other colouring-matter. The inter- 

 mediate stages of the process were as in other of the chromotype processes, 'and the 

 coloured gelatine was made to receive a printing ink, and impressions were taken 

 therefrom. In 1865 he improved his process as follows : When the image is pro- 

 duced by means of a negative that is employed to produce an impression of the sensi- 

 tive gelatinous tissue, previous to its development the tissue is mounted upon a surface 

 of glass, and the uncoated surface of the glass is placed towards the light. Warm 

 water is used to dissolve the soluble portions of the gelatinous coating, and thus to 

 develop the image. The plate bearing this image is surrounded with a rim, hardened 

 by means of a protosalt of iron or of sulphate of alumina. The surface is coated with 



