A Manual Of Photography

POLISHING THE PLATE. 241 Section II.—Polishing the Plate. Upon this subject but little remains to be added to what is stated in Daguerre’s earliest form of manipulation, and the few remarks just quoted from the Comptes Rendus. It is of the utmost importance tliat a very perfect mirror sur- face should be produced, and to ensure the utmost freedom from all organic matter during the polishing, the plate-holder repre- sented in two positions by e e, in Pig. 66, has been devised. The plate-holder is secured to a table by a clamp, and the plate to be polislied is fixed upon the horizontal surface of the plate- holder by means of four binding-screws placed at its corners. The plate having undergone the preliminary rubbing, which, as being a comparatively coarse operation, need not be further de- tailed than it is in the earlier section, and having been fixed on the holder, the last polish is to be given to it. The hand- buff, £,in Pig. 66, is to be dusted over with animal char- coal, and moistened with a little spirits of wine: some ope- rators employ tripoli in a state of impalpable powder mixed with essential oil of lavender. If, however, any essential oil is used, it must be ascertained to be quite free from castor oil,—with which it is very commonly adulterated,—by placing a drop on a piece of paper : if it is a pure essential oil, it will, when warmed, entirely evaporate, but if not, a greasy spot will remain. In M. Claudet’s establishment, where, from long experience, the best modes of manipulation are introduced, the last buffing is effected in a somewhat different manner. In a box on a roller, to which there is a handle, Pig. 61, is 61. placed a long piece of drab-coloured velvet, which can be drawn out and extended, by means of a second roller, upon the per- fectly flat table. The first foot or two, for example, is drawn out: the plate, which has already received its preliminary polishing, is placed face downwards, and being pressed close with the fingers a rapid circular motion is given to it, and in a few minutes it