ELEMENTARY PHOTO-MICROGRAPHY. 6 1 



completed on a bright day in a little over an hour, 

 though on dark days the printing is slow. Moisture 

 is the chief preventive of successful work ; there- 

 fore paper, wood frames, and place of exposure 

 must be dry. 



The platinotype paper itself is supplied in sealed 

 tins, twenty-four sheets, quality A. A. 4^ in. by 

 3% in. for is. 6d., from which it should be removed 

 for preservation to a special tin tube having a false 

 bottom, under which calcium chloride is kept to 

 absorb any moisture, and the joints of this tube are 

 further protected by a wide rubber band. Thus 

 protected, the paper will keep in good condition 

 many months. The lemon coloured surface of plati- 

 num paper is more sensitive to light than is that of 

 P.O. P. ; consequently, the placing of the paper in 

 the frames, the examination of prints, and develop- 

 ing must be done in dull light. After the sheet of 

 platinotype paper is put on the negative it is de- 

 sirable, though not essential, to add a protecting 

 sheet of rubber or waterproof paper before fastening 

 the back of the printing frame. During exposure, 

 which must be by daylight, an occasional peep at 

 the paper will show how far printing has proceeded. 

 The image is only faint grey when finished, but 

 every detail should be seen, however feeble. If 

 there be any part of the print that should be pure 

 white when finished, the attention should be fixed 

 on that spot, and its tint compared with that of the 

 edges of paper. So long as this is the same lemon 

 colour it may be gathered that printing is not car- 



