40 



PHOTO-MICROGRAPHY 



water, to which was finally added 3 or 4 drops of commercial carbolic acid. The 

 plate carefully cleaned with spirit and water and plenty of rubbing. The albumen 

 solution was poured over it, several plates being done at one time, and drying was 

 afterwards effected spontaneously in a dust-proof cupboard. When coating these 

 plates with the bromo-iodised collodion, each one is held in the left hand, whilst the 

 right one is occupied with pouring the collodion from its specially-capped bottle on to 

 the centre of the plate in a little pool. The plate is tilted so as to flow the collodion 

 in one wave — and only one — all over it equally, the surplus being quickly returned to 

 the bottle, which is instantly covered. The operator is careful now not to incline the 

 plate more in one direction than in another, or there may result a crease from this 

 cause on the film. Presuming he accomplishes this satisfactorily, he watches for the 

 material to " set," and just when it has — let him try the edge at one corner to make 

 certain — he places it into the silver bath, resting it on the dipper. When on lifting 

 the slide out he sees no greasiness of the film, which is generally effected in about 

 three minutes in summer and six in winter, he places it on the slide, which, by the 

 way, should be made for wet plates, having silver wire corners. It is needless to say 

 contact is out of the question, so all transparencies of negatives must be taken with 

 the camera and lens, the limelight condenser already explained being used if daylight, 

 which is much quicker, cannot be utilised. Development with one of the many 

 formulse is carried out in the usual manner, great care being exercised in pouring the 

 fluid over the plate to do so with one sweep of the hand. The following recipe is a 

 very good one : 



Ferrous sulphate . . . . . . . 10 grains. 



Glacial acetic acid . . . . . . . 15 minims. 



Alcohol . . . . . . . . . 15 to 20 minims- 

 Water ......... I ounce. 



As the silver bath gets old — more and more silver crystals being added from time 

 to time to keep up its strength — more and more alcohol is required in the developer to 

 make it flow evenly. This hint should not be forgotten. 



Washing, fixing, and drying are carried out in the same manner as with the dry- 

 plate collodion plates. 



As all collodion films are so tender every lantern-plate must be varnished. 

 Rouch's transparent variety for wet plates we have always found to be excellent, but 

 most wet plate dealers supply varnish equally good. 



If the slide after development appears rather flat, intensification may be resorted 



