500 ANNUAL RECOUP OF SCIENCE AND INDUSTRY. 



soda when intended for long preservation. They are gener- 

 ally, however, not designed to be kept a great while. 14 C, 

 CXCIX., 1871, 331. 



EDWARDS'S IMPROVEMENT OF THE ALBERTYPE PROCESS. 



We have already referred to the importance of some of the 

 later improvements for the reproduction of photographic pic- 

 tures by carbon ink from the photograph itself, without the 

 use of any of the salts of silver, the result being a much great- 

 er economy of time and cost, and an absolute permanency of 

 the print. The more important of these methods are those 

 known as the "Woodbury" and the "Albert" processes, and 

 both have lately come extensively into use both in Europe 

 and America, and are employed in the reproduction of ];>lates 

 for illustrated works. An English artist, Mr. Ernest Edwards, 

 has, it appears, been improving upon the Albert process until 

 he has succeeded in obtaining what he and others call the per- 

 fection of the art. This method, in its present manipulation, 

 consists in coating evenly with wax the plate of glass, the sur- 

 face of which has been ground, but not polished, and then 

 pouring over it a sufficient quantity of a mixture of gelatine, 

 bichromate of potash, and chrome alum, so as to form, when 

 spread out and subsequently dried, a film of the thickness of 

 a very thin card. The chrome alum is of great importance 

 in preventing the subsequent solubility of the film, as it has 

 the property of preventing the gelatine from again becoming 

 liquid after it is set ; and without the use of some such pro- 

 cess it would be entirely impossible to carry on the work suc- 

 cessfully. The usual proportion of bichromate of potash to 

 the gelatine is about five per cent., although this varies for 

 different applications. 



After the glass has been coated it is maintained in a level 

 position for a few minutes, until the film has set sufficiently 

 to permit its being placed edgewise, and stored away in .a 

 suitable drying-room to dry an operation which usually oc- 

 cupies about twenty-four hours. After this the film is re- 

 moved from the glass, the operation being facilitated by the 

 use of the substratum of wax. This constitutes one of the 

 most important advances of the Edwards-process over the Al- 

 bert, for various reasons that it is not necessary here to ad- 

 duce. The film is then to be subjected to the action of the 



