PRACTICAL PHOTO-MICROGRAPHY. 149 



Put into a clean cup about 10 drops of a solution of argentic 

 nitrate, bath strength, acidified with nitric acid, add thereto 

 about 4 drams of the pyro, or iron developer, pour this on the 

 plate, but keep it moving, and beware of turbidity. Wash the 

 plate. 



The color may not be pleasing at this stage, in which case 

 we resort to toning. Immerse the plate in 



Platinic chloride 1 grain 



Nitric acid 1 minim 



Water 3 ounces 



Watch the progress and remove the plate when the color is 

 satisfactory. A fine color (engraving black) may be obtained 

 by toning in this solution till the image is bleached and almost 

 disappears, and then lightly intensifying with iron and silver 

 as above. 



MR. ARMSTRONG'S PALLADIUM TONING FOR SLIDES. 



Palladic Chloride 15 grains 



Water 15 ounces 



Nitric acid a trace 



For each ounce of toner take 1 dram of this and 7 drams of 

 water. Tone till the color penetrates right through the film, 

 and is visible from back of the plate. 



After the plate is dried and varnished with a clear varnish, 

 (see page 60) it is cut down with a diamond to proper size. 



GELATINE CHLORIDE PLATES FOR SLIDES. 



Print in contact. As even with gas or oil light the exposure 

 may be inconveniently long, a good plan is to burn a measured 

 length (say 1 inch) of magnesium ribbon at certain distances, 

 determined by trial, from the frame. For a beginning the inch 

 of ribbon may be burned at 10 inches distance for a moderately 

 dense negative. The exposure to diffused daylight may be 

 from 5 seconds upwards. If magnesium be used a spirit-lamp 

 may be utilized to ignite the ribbon, a spirit-lamp would require 

 a very long time to impress the plate. 



Devolopment is performed in a flat dish, the plate being 

 placed therein face upwards, and the developer poured over 

 the plate. 



