LOW-POWER WORK 



41 



to, and this is done at once by pouring over the fihxi some of the following, to 

 which has been added a few drops of silver nitrate dissolved in distilled water (about 

 2 per cent.) : 



Pyrogallic acid 2 grains. 



Citric acid . . . 3 grains. 



Water . . . . . . . . . i ounce. 



After fixing, intensification may also be performed, but the solution is different 

 and the eflPect very often prohibitive, as the film nearly always turns yellow or of an 

 ugly colour. In our experience it is quicker and far more satisfactory to make 

 another exposure rather than tinker with a lantern slide. With a negative it may be 

 different. 



The faults that may arise by this process are many. The following are the 

 leading ones : 



1. If the plate, after development, appears foggy in patches, probably the plate 

 has not been properly coated with albumen, or is not clean. 



2. If patches are transparent in bubbly-looking spots probably bubbles have been 

 present, and so have prevented the plate being properly sensitised in the bath. 



3. Streaks and irregular markings suggest a damp plate in parts. 



4. Streaks all over and general irregularity in the film, some parts much more 

 coated than others, usually arise from badly coating with the collodion, parts becoming 

 drier than others before putting in bath. 



5. Comets and pin-holes often come from dirt either in the collodion or on the 

 plate. 



6. Marks of deposited silver on the edges arise nearly always from a dirty 

 slide. 



7. Flat pictures nearly always mean a dirty bath. To remedy expose it to the 

 sun and filter. Avoid a too acid bath, but equally so an alkaline one. 



(iii) PRINTING POSITIVES ON PAPER OF DIFFERENT KINDS 



Seeing that many may very possibly conduct their photography at evening time 

 rather than during the day, we will describe first how to take a print on paper which 

 can be exposed in front of the gaslight. We refer again to the excellent paper for all 

 photo-micrographical work, namely, that sold under the name of Eastman's " Nikko 

 paper." There is not space here to describe many varieties of bromide paper, but 

 having tried most of them, we have found that ordinary bromide paper gives too 



