116 PRACTICAL PHOTOMICROGRAPHY. 



jacent image and the fineness of division of the gold itself. 

 The fixing operation does not remove the tone produced by the 

 gold ; and, moreover, the gold imparts to the image an ability 

 to withstand atmospheric and other actions which but for the 

 gold would soon destroy the beauty of the image. 



The paper is almost always bought ready albumenized and 

 " salted," and very frequently ready sensitized also ; in the 

 latter case special processes are resorted to in order to make 

 the paper keep good for a period of weeks or even months. 

 We prefer the ready sensitized paper for general work, and in 

 Britain it is easily obtained at very reasonable prices. 



If, however, sensitized paper cannot be obtained, the albu- 

 menized salted paper is to be floated albumen downwards in a 

 bath of argentic nitrate. (See page 64.) Time of floating 

 3 to 5 minutes according to .temperature and nature of the 

 albumenized paper. The higher the temperature the shorter 

 should be the flotation. 



The " bath " formulated on page 64 should be neutral or 

 slightly alkaline, and must be kept up to strength, for of course 

 each sheet of paper floated on it removes a certain quantity of 

 silver. 



When the negatives are " thin," full of detail but lacking 

 contrast, the 60-grain bath or a strong bath should be used 

 and full time of flotation given. " Hard " negatives may be 

 printed on lightly sensitized paper, that is to say on paper 

 floated on a weak bath, and only long enough to ensure com- 

 plete conversion of the salt in the paper into silver salt. The 

 ready sensitized papers usually give more brilliant prints, or 

 more contrast, than paper sensitized at home and used imme- 

 diately without " preservatives." 



A hard negative is best printed in direct sunlight ; a very 

 thin negative should be printed in weak light, or in brighter 

 light behind a sheet of ground-glass. 



When flotation is finished, the sheet of paper is to be hung 

 up in a cool dry place to dry ; nothing must touch the face 

 while it is damp, and the corners should not be allowed to curl 

 inwards and so spoil the centre of the sheet. It is well to blot 

 off each sheet as it leaves the sensitizing bath, having allowed 



