W. Crookes on the Wax-paper Photographic Process. 177 



63. No rule can be laid down for the proper time of exposure; 

 it will depend upon the quality of the light, and intensity of the 

 negative ; some pictures being completed in a few minutes, others 

 requiring upwards of half an hour. The printing should always 

 go on until the picture is several shades darker than ultimately 

 required. A very little experience will enable the operator to 

 judge so well of the quality of the light, as hardly ever to have 

 a failure. If the two sheets of paper be stuck together in two 

 or three places at the edge3 with small pieces of gummed paper, 

 the frame can be removed to the dark room, and the progress of 

 the sheets examined; but this is always attended with some 

 danger, for unless they are replaced without having been shifted 

 one from the other, there will be a double image. 



64. As soon as the picture is considered to be printed sum- 

 eiently deep, it has to be fixed. 



The fixing bath consists of 



Saturated solution of hyposulphite of soda 10 ounces. 

 Water 30 ounces. 



This bath will be found to fix the pictures perfectly, but they 

 will generally be of a reddish tint ; if it be thought desirable to 

 obtain the pictures of some shade of dark brown, or black, it 

 will be necessary to employ a bath made as follows ; 



Saturated solution of hyposulphite of soda 10 ounces. 

 Water. . . . . . .10 ounces. 



Exhausted positive exciting solution (61) 10 ounces. 



Mix these together and then add the following ; 



Water 10 ounces, 



Chlorid of gold 20 grains ; 



taking care in mixing to pour the solution of gold into the solu- 

 tion of hyposulphite, and not the latter into the former, or 

 another decomposition will be produced. 



Pour this mixture into a dish, and lay the positive carefully 

 on it, face downwards. As soon as it is thoroughly damp, 

 (which may be known by its becoming perfectly flat after having 

 curled up,) immerse it totally in the liquid. 



65. The pictures should not be too crowded in the bath, as 

 they are very apt to become irregularly colored in places where 

 the hyposulphite has not had free access during the whole of the 

 time. When first put in, the color will change to a light brown, 

 and in the course of some time, varying from ten minutes to two 

 or three hours, it will pass through the different shades of brown 

 to black and purple, gradually fading in intensity during the 

 time. It will be necessary to allow the picture to remain in this 

 bath for ten minutes at least in order that it may be perfectly 



SECOND SERIES, VOL. XXII, NO. 65. — SEPT., 1856. 



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