ENGRAVING IN AQUA TINTA. 439 



the desired depth ; and as the plate is not corroded 

 so deep, it soon wears out in printing; whereas 

 coarser grains are firmer, the acid goes deeper, and 

 the plate will throw off a great many more impres- 

 sions. The reason of all this is evident, when it is 

 considered, that in the fine grains, the particles are 

 small and near each other, and consequently the 

 aqua fortis, which acts laterally as well as down- 

 wards, soon undermines the particles, and causes 

 them to come off. If left too long on the plate, 

 the acid would eat avvay the grain entirely. 



On these accounts, therefore, the moderately 

 coarse grains are more sought after, and answer 

 better the purpose of the publisher, than the fine 

 grains which were formerly in use. 



Although there are considerable difHculties in 

 laying properly the aqua tint grain, yet the corrod- 

 ing the copper, or biting-in, so as to produce ex- 

 actly the tint required, is still more precarious and 

 uncertain. All engravers allow that no positive 

 rules can be laid down, by which the success of 

 this process can be secured ; nothing but a great 

 deal of experience and attentive observation can 

 enable the artist to do it with any degree of cer- 

 tainty. 



There are some hints, however, which may be 

 of considerable importance to the person who 

 wishes to attain the practice of this art. It is evi- 

 dent, that the longer the acid remains on the cop- 

 per, the deeper it bites, and consequently the 

 darker will be the shade in the impression. It 

 may be of some use, t'lerefore, to have several bits 

 of copper laid with aqua tint grounds, of the same 

 kind to be used in the plate, and to let the aqua 

 fortis remain for different lengths of time on each ; 

 and then to examine the tints produced in one, 



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