36 



THE ALUMNI JOURNAL. 



permanent one, because the iodide of 

 potassium dissolved out the white parts 

 that were not affected "by the light. 

 From this negative he obtained other 

 prints. 



Now, various modifications of Fox 

 Talbert's process, were brought out, and 

 a man named LaGray. I think (or at 

 least it was just about the time he lived) 

 conceived the idea of making these pic- 

 tures more transparent by waxing them. 

 That was the first good negative we had. 

 It was a modification of Fox Talbert's 

 idea, only he waxed the paper. Then 

 about the same time it was found that a 

 mixture of chloride of iron and cyanide 

 of potassium, when mixed together were 

 acted upon by light. Herschel discovered 

 this, and that was the way we obtained 

 the blue print, which is far older than the 

 photograph. Sir John Herschel found 

 that a mixture of chloride of iron and 

 cyanide ol potassium, when exposed to 

 sunlight made Prussian blue. So that if 

 you take paper and coat it with this mix- 

 ture and then expose it under a negative 

 you get a blue picture. 



The trouble with these paper pictures 

 was that you could not eliminate the 

 grain of the paper, and if you will ex- 

 amine these close enough you will see 

 that they are blurred. This one printed 

 from that particular negative is blurred 

 — very much blurred. These sensitive 

 silver compounds are so sensitive that 

 the grain of the paper produces an im- 

 pression. Now, in 1848, Niepse, a 

 nephew of the first Niepse, thought it 

 would be a good idea to use glass plates 

 coated with albumen. He took chloride 

 or iodide of silver, mixed it with white 

 of egg, spread it on plates, heated the 

 plates, which, of course, coagulated 

 the albumen, and that fixed his film 

 upon the glass plates. That was 

 quite a step. Now, we had gotten 

 rid of the paper. By the way, I made a 



little mistake there about the way he got 

 the picture. He got the picture by put- 

 ting salt in the albumen and then coagu- 

 lating it, and then he dipped the plate 

 into a solution of silver nitrate and in 

 that way got the precipitate in the film 

 itself. This was important but trouble- 

 some and not always successful. 



Now, a few years before another dis- 

 covery was made. Remember that this 

 was in 1848 that Niepse worked with the 

 albumen process. In 1840, Schurben, a 

 Swiss chemist, discovered gum cotton. 

 This gum cotton is a nitrated compound 

 of cotton, made by the action of concen- 

 trated sulphuric and nitric acids upon 

 cotton. Sometime afterwards Maynard, 

 a Yankee, in Boston, discovered that this 

 gum cotton was soluble in alcohol, and 

 ether, and then he found that by evapor- 

 ating the substance he got the thin film o 

 collodion. Scott Archer, an Englishman, 

 conceived the idea of using this film as a 

 vehicle for these particularly sensitive sil- 

 ver salts for photographing. His method 

 was pretty much that which is followed 

 to-day and that is still in use to quite a 

 large extent. 



In this process we have this series of 

 operations : First, the plate must be per- 

 fectly clean. That is essential. Any 

 little spot upon it will form a nucleus 

 which will spread over the surface of the 

 plate. The plate is then coated with al- 

 bumen and allowed to dry without heat- 

 ing. It is then flowed with this collo- 

 dion, and in the collodion is put the chlo- 

 ride, iodide or bromide of silver, which 

 you need. It is generally the chlo- 

 ride, iodide or bromide of silver. This 

 collodion is afterwards dipped into a sil- 

 ver bath, and then we get the sensitized 

 silver surface, very thin and perfectly 

 transparent. It is then ready to go into 

 the camera. It is put into the camera 

 soaking wet with nitrate of silver. It is 

 exposed and then developed with a solu- 



