ETCHING. 429 



thoroughly dry, the aqua fortis may be poured on 

 again, to bite the other lines that are required to 

 be deeper. 



This process of stopping-out and biting-in is to 

 be repeated as often as there are to be lines of dif- 

 ferent degrees of thickness, taking care not to 

 make any mistake in stopping-out wrong lines. 



It is also necessary to be particularly careful to 

 stop-out with the varnish, those parts from which 

 the ground may happen to have come off by the 

 action of the acid, otherwise you will have parts 

 bit that were not intended, which is called foul- 



When the biting-in is quite finished, the next 

 operation is to remove the bordering-wax and the 

 ground, in order that you may see what success 

 you have had ; for till then, this cannot be known 

 exactly. 



To take off the bordering-wax, the plate must 

 be heated by a piece of lighted paper, which soft- 

 ens the wax in contact with the plate, and occa- 

 sions it to come off quite clean. 



Oil of turnpentine is now poured upon the 

 ground, and the plate is rubbed with a bit of linen 

 rag, which removes all the ground. Lastly, it is 

 cleaned off with whitening. 



The success of the etching may now be known, 

 but it is necessary to get an impression taken upon 

 paper by a copper-plate printer. This impression 

 is called a proof. 



If any parts are not bit so deep as were in- 

 tended, the process may be repeated, provided the 

 lines are not too faintly bit to admit of it. This 

 second biting-in the same lines, is called re-biting, 

 and is done as follows : Melt a little of the etching- 

 ground on a spare piece of copper, and dab it a 



