MECHANICS AND USEFUL ARTS. 127 



PHOTOGRAPHS WITH A WHITE SURFACE. 



Put into a small mortar a teaspoonful of kaolin ; add thereto 

 about a quarter of an ounce of sensitive collodio-chloride, and ^tir 

 well with the pestle until it becomes a smooth paste. Add to this 

 three-fourths of an ounce more of the collodion, and again stir, and 

 pour the whole into a bottle with one or two drops of castor-oil. 

 bhake well, and place it aside until the coarse particles have sub- 

 sided. 



Edge a piece of talc or glass for about a quarter of an inch all 

 round with dilute albumen, afterwards coat with the kaolin collo- 

 dion, and dry by gentle heat, when the talc or glass, if placed 

 upon a piece of white paper, will have the appearance of alabas- 

 ter. 



If the film splits, it should have a trifle more castor-oil in the 

 collodion ; but the best remedy is to choose a more powdery 

 collodion. 



If the film is upon glass, the progress of printing may be exam- 

 ined from the back ; but if talc be the medium used, it may be 

 turned back in the same manner as when i3rinting upon paper. 



Tone, fix, and wash in the same manner as with an ordinary 

 collodio-chloride print upon opal glass, and mount in a frame or 

 case, to protect the picture from being scratched. It must not be 

 varnished. 



After 3 years' trial the film has been found not to crack or leave 

 the talc or glass after the picture has been once finished. 



Many pretty eftects may be produced by putting different col- 

 ored papers behind vignettes produced in this way, as whatever 

 color is placed behind the picture gives a delicate tinge of that 

 color to the picture. 



Talc may be obtained in sheets as large as 10 by 8 inches. 



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IMPROVED PHOTOGRAPHIC PAPER. 



The "British Journal of Photography " publishes the following 

 by W. H. Davis: " My method for preparing the surface — for 

 I believe it will do for many other surfaces than paper — is the 

 following for direct printing: Take from 4 to 6 grains of 

 gelatine, soak it in an ounce of water for an hour, then melt it 

 gently over a fire, hot plate, or water-bath, using a clean earthen 

 pipkin. When fully dissolved, add to it» while yet warm, and 

 stirring it gently during the mixing, from 4 to 6 drachms of a 

 solution of white lac in methylated spirit, if for white or pale sur- 

 fiices ; but orange lac will do if the surface be of a darker color. 

 This is made in the proportion of 6 ounces of spirit to one ounce 

 of lac, and digesting it till fully dissolved. The mixture of the 

 gelatine and gam lac in spirits produces a creamy-looking emul- 

 sion, to which is add(;d 4 grains of chloride of sodium, or a like 

 equivalent of chlorides of ammonium or barium, and, when fully 

 dissolved, filter through fine muslin into a clean pijpkin, and it is 

 ready for use. 



