80 PHOTOQEAPHIC PROCESSES. 



should remain till all the unaltered salts are dissolved 

 away, this is known by the creaminess having dis- 

 appeared from the back of the plate; it is then 

 washed in frequent changes of water for several 

 hours, and finally put aside to drain. 



When dry, the plate is warmed before a clear fire, 

 the temperature not being raised higher than the 

 hand can very comfortably bear, the varnish is then 

 applied in exactly the same manner as collodion, and 

 when all superfluous fluid has drained away, heat is 

 again applied ; the temperature being carried much 

 higher than at first, to prevent the formation of a 

 mat surface. Should the intensifier not be used, and 

 the plate found to lack density after fixing, the 

 mercurial solution mentioned in the following process 

 may be applied, (as little exposure to actinic light as 

 possible being given before its application). 



When the reproduction of very minute markings 

 is necessary, dry plates never give as good results as 

 the wet, at least in our hand; they are, however, 

 sufficiently perfect for all practical purposes, while 

 the shortness of the exposure, cleanliness of manipu- 

 lation, and when purchased, the time saved by the 

 absence of any previous preparation, almost counter- 

 balance this disadvantage. 



Great care is required in using these plates, as the 

 slightest glimpse of actinic, light will utterly spoil 

 them. A double thickness of ruby glass must be 

 substituted for the ordinary yellow glass of the dark 

 room, and even of this light, as little as possible 



