Proceedings of the Photographical Section. 981 



A general discussion was then had upon the various methods of 

 preparing and applying albumen substratum for collodion negatives. 



Mr. II. J. Newton said, by using a substratum of albumen to 

 which ammonia had been added, the film was much thinner than when 

 plain albumen was used. 



Mr. D. Chapman had found that the method of preparing and the 

 time of applying the albumen substratum was very important. By 

 some methods the plates were rendered much less sensitive. His 

 method of preparation was to dissolve one ounce of albumen in 

 twenty ounces of water, to which one dram of strong aqua ammonia 

 had been added. After standing one month, filter, and it is in fit 

 conditon for use. In time it will assume a tinge of red, and is then 

 in the very best condition, and would render the superimposed collo- 

 dion film one-fifth more sensitive than if used when first made. 



Mr. H. J. Newton exhibited several very fine negatives by the 

 gum tannin process, the details of which he had given at the Novem- 

 ber meeting of the Section. He had somewhat modified the developer, 

 by adding to the stock solution one ounce of acetic acid No. 8 to 

 12. His sensitizing bath contained forty-five grains of nitrate of 

 silver to the ounce of water, and was slightly alkaline by the addi- 

 tion of ammonia. The prints from the negatives exhibited by Mr. 

 Newton were much admired for the delicate, harmonious effects pro- 

 duced. 



A general discussion upon photographic literature followed Mr. 

 II. T. Anthony's reading of an editorial in the December number 

 of the Philadelphia Photographer. 



In answer to inquiry, Mr. D. Chapman stated that plain collodion 

 could be sensitized, and fully ready for use in one hour by the fol- 

 lowing method: 



Use\ five grains iodide of cadmium and one and one-half grains 

 bromide of ammonium. The bromide should be thoroughly ground, 

 and dissolved in the alcohol used in making the plain collodion. The 

 desired tint is then produced by addition of tincture of iodine ; after 

 filtering, and standing the length of time named, it is ready for use- 

 By substituting the bromide of magnesium for that of •ammonium, a 

 very smoothly working collodion of great permanence was produced, 

 though he had found it to be about one-tenth less sensitive than that 

 containing ammonium. 



Mr. II. T. Anthony stated that all collodions which were prepared 

 by first adding the bromide salts were much more sensitive than 



