A Manual Of Photography

242 PRACTICE OF PHOTOGRAPHY. receives its highest lustre. As the velvet becomes blackened by use it is rolled off, the portion remaining in the box being always perfectly clean, and ready for use. The plate is now ready for receiving its sensitive coating, and, to avoid the chance of the surface touching any other object, M. Claudet adopts the simple but most effective mode of pushing it from the buff into a spherical wooden bowl, in which the plate rests by its four corners in perfect security. As the edges of the metallic plates are generally sharp, they would often cut the buffs, were that accident not prevented by a suitable precaution. Tig. 62 re- 6T^-—-— presents an apparatus called a plate- 5 bender. The surface a is perfectly horizontal, and has a steel border near 62. the bar b: upon the bar bruns a press that carries a steel knife edge so rounded as to be able to bend a plate but not to cut it. The silver plate that is to buffed is placed on this apparatus with an edge close to the back bar, and the press is then run along it from end to end, by which means the edge of the silver plate is bent downwards in a very slight degree, but sufficient to prevent any cutting action on the buffs. Ail the four edges of cacti plate are bent in the same manner. Section III.—To Give the Sensitive Surface to the Plate. Various compounds, called accelerating liquors, have been in- troduced, in all of which we have combinations in various pro- portions of either bromine and iodine, or chlorine and iodine, and sometimes of the three. These are known by the names of Eau Bromeé, or Bromine Water, Bromide of Iodine, Bedman's Sensitive Solution, Hungarian l àquid,and Wooleott's Accelerating American Fluid. In al1 cases, bromine, combined sometimes with chlorine and iodine, is the accelerating agent. They all require to be diluted with water until about the colour of pale sherry. Ihe plate is exposed to the influence of the vapour in the same manner as with the iodine, the iodine being applied first by the method directed by Daguerre, but the colour to be attained differs accord- ing to the solution employed. An iodizing box is shown at c, Fig. 66: at the bottom of this some iodine is strewed, and in general it is covered with a little sand or a card; this is to avoid the irregular action on any part of the plate: the box being adjusted with a cover, the iodine is preserved from evapo- ration and lasts a long time. When the plate has assumed its