102 PRACTICAL PHOTOMICROGRAPHY. 



To INTENSIFY. 



The negative being above suspicion of hypo is soaked in a 

 flat dish in the solution of mercuric bichloride and acid given 

 on page 63. When the film is as pale gray as it will be- 

 come, it is well washed and placed in the solution 5, given on 

 the same page. Here it will very quickly turn black or 

 brown ; but it must be left in the sodic sulphite till it is dark 

 when seen from the back as well as from the front. It is then 

 washed, and will be found to have gained greatly in density 

 and printing quality. 



There are many other methods of intensifying for which we 

 refer the reader to the photographic literature of the day. We 

 have given the one we prefer to all others, especially for photo- 

 micrography. As a rule, however, intensification is to be 

 avoided, for it is not only ticklish to perform but doubtful 

 under conditions not precisely established as to its perman- 

 ence. 



If the finished negative is too dense, especially if the shad- 

 ows are clogged, we may have recourse to " reduction," which 

 does not present the same difficulties as intensification. 



REDUCTION. 



To Mr. Howard Farmer we are indebted for a very simple 

 and effective system of reducing. (See page 63.) 



Soak the plate, carefully freed from acid after the acid alum 

 bath, in solution B, for 3 minutes. Put into a cup a few drops 

 of the solution A, and pour the hypo-solution into the same 

 cup, then returning the mixture to the dish holding the plate. 

 Reduction will at once begin and its progress must be watched. 

 If the action cease before sufficient effect is produced add more 

 of A. When finished wash well and dry. The Reducer No. 

 2, given on page 63, may be used. The plate is soaked in 

 A till a gray film more or less marked seems to cover the im- 

 age ; the plate is then washed and placed in solution B. 



VARNISHING. 



If a large number of prints are likely to be wanted from a 

 negative it is well to varnish with a spirituous solution of shel- 



