After every precaution for obtaining a good grain, the process is still liable to great uncertainty, and often fails in the hands of the most experienced artists. The same ingredients do not always give solutions possessing the same qualities ; and the nature of the grain is also ma terially affected by the state of the weather. Hence it is sometimes necessary to employ several grains before a proper one is obtained. To add to these difficulties, the inclined position in which the plate is held, in order to give the fluid an equable diffusion over its surface, causes a greater proportion of the solution to descend to the lower parts, and consequently renders the grain there less fine. This disadvantage is, however, in some degree counteracted, by making the coarsest side the foreground, as that part has generally the deepest sha dows.
The finer grains yield impressions which most nearly imitate drawings, and resemble the effects of Indian ink ; but they are apt to come off before the acid has remained sufficiently long to produce the necessary depth, and give few good impressions. On the other hand, the coarser grains admit, by their texture, a lon ger action of the aquafortis, which thus entering deeper into the plate, renders it capable of throwing off a greater number of impressions. For this reason, grains of a
moderate coarseness are now generally preferred to the finer grains which were formerly employed. The diffi culty of procuring a proper grain, is by no means the sole obstacle to be overcome in aquatint engraving : The corroding the copper with acid is an operation of still greater nicety; and the success of it can only be secured by long experience and attentive observation : When every thing succeeds well, the process is simple and expeditious ; but this is seldom the case, and errors which may have been committed, are corrected with great difficulty.
This species of engraving seems to be best adapted for landscapes and imitations of washed drawings ; but, as it is incapable of representing rapid transitions, and nice discriminations of tints, it ought never to be ap plied to highly-finished subjects.
Engraving in aquatinta was invented by Le Prince, a French artist, by whom the process was long kept se cret : It is even said, that for some time he sold his prints, which are still reckoned excellent specimens of the art, as drawings. It was introduced into this coun try by Mr Paul Sandby, and afterwards communicated by him to Mr Jukes. It is now known all over Europe ; but no where practised with greater success than in this kingdom. (it. R.)