The Dark Room: Developing and Printing 53 



action is slow and it is liable to stain the plates. 

 In the winter a plain hypo bath of one part hypo 

 to four or five parts water may be used, but this 

 should be made fresh every day. In the summer 

 the acid bath should be used. This is made by 

 adding two hundred grains of acetone sulphite 

 to every quart of a twenty per cent solution of 

 hypo. There are many other formulas for acid 

 fixing baths, but I have found this one to be the 

 simplest and best. It not only hardens the film 

 of the plate sufficiently to prevent it from " frill- 

 ing" or "blistering" (which is the object of the 

 acid bath, for plates will invariably do this in the 

 warm weather if they are not hardened), but it 

 clears the plate perfectly and will keep in good 

 condition for an almost indefinite period. 



Another good hardener is formaline (use one 

 part to about thirty parts of water), but its only 

 bad feature is the fact that if we are not very 

 careful it is likely to harden the film so much 

 that it will be impossible to either reduce or in- 

 tensify it afterward should we so desire. The 

 plate should be placed in this solution immedi- 

 ately after being taken from the hypo (of course 

 when using this the acid bath is unnecessary) and 

 allowed to remain in it from one-half a minute to 

 three minutes according to the strength of the 

 solution. This solution will keep well and may 

 be used repeatedly until it becomes too weak. 



