Without allowing the plate to dry, it is then put in the caustic 

 potash, and the capsula being placed upon the stand, the potash is 

 heated up to the boiling point ; it is then left to cool (I>) ; and be- 

 ginning again the operations described from A to D, a second biting 

 is obtained ; and by repeating again the operations described in A 

 and B, a third biting is produced. The plate is then dried ; in this 

 state the black parts of fhe plate are filled with chloride of silver. 



The plate is then polished until the white parts are perfectly pure 

 and bright. This polishing is done with cotton and " ponce" 

 (pumice stone); afterwards, the chloride of silver, filling the black 

 parts, is cleansed by the means described in B and ('. The plate is 

 then dried ; but before drying, it^is well to rub the plate slightly 

 with the ringer, in order to take off from the black parts any 

 remains of an insoluble body which generally remain on it. The 

 preparatory engraving is then finished, and the plate has the 

 appearance of a very delicate aqnatint engraved plate, not very 

 deeply b'tten in. 



Nevertheless, if the operation has been well managed, and has 

 been successful, it Is deep enough to allow the printing of a con- 

 siderable number of copies. 



Note. Sometimes, instead of treating the plate with the boiling 

 potash in the capsula, a similar result may be obtained by placing 

 the plate upon the stand, covering it with the solution, and heating 

 it by means of a spirit-lamp, until, by evaporation, the potash be- 

 comes in a state of ignited fusion. By this means the grain is finer, 

 but the white parts are more liable to be attacked. 



Last operation of biting in. This operation requires some of the 

 re-agents before named, and also, 



1. A siccative ink, made of linseed oil, rendered very siccative by 

 boiling it sufficiently with litharge; it may be thickened wilh 

 calcined lamp-black. 



2. An electrotype apparatus, and some solutions fit to gild and 

 copper the plate. 



Means of operating. The plate must oe inked as copper-plate 

 printers do, taking care to clean off the white parts more perfectly 

 than usual ; the plate is then to be placed in a room sufficiently 

 warm, until the ink is well dried, which requires more or less time, 

 according to the nature of the oil employed. The drying of the 

 oil may be hastened by heating the plate upon the stand with the 

 lamp, but the slow process is more perfect and certain. 



