108 THE BOOK OF THE LANTERN. 



rendered sufficiently acid with nitric acid to slightly redden 

 litmus paper. If the operator is careful to follow these 

 directions he will have no difficulty in toning his trans- 

 parencies with platinum. 



We may summarise the order of operations as follows : 



Albumenise the glass. 



Dry. 



Coat with collodion. 



Sensitise in silver bath. 



Expose. 



Develop. 



Fix in hypo. 



Wash. 



Clean with iodide solution if necessary. 



Tone with platinum. 



Wash. 



Dry. 



The operations conclude with giving the film a coat of 

 transparent varnish. Any good varnish may be used, but 

 care must be taken if the slides are to be subsequently 

 coloured, that some varnish upon which turpentine has no 

 action be employed; otherwise the turpentine used in 

 colouring will most surely mingle with the varnish and 

 ruin the picture. 



It is hardly necessary to add that the operations of sen- 

 sitising, developing, and fixing the plate must be conducted 

 in a non-actinic (red) light, and that all precautions usually 

 taken in dealing with photographic chemicals must be 

 observed. The directions are written for those who have 

 already mastered the details of such work. 



