The transparent portions of the negative which give too dark a complexion on the positive can be filled up by careful stippling or interweaving pencil lines until they are brought into harmony with the surrounding parts. Pimples, freckles, blotches, etc., are thus removed, and the wrinkles and exaggerated lines softened down. This is what is termed smoothing the face.
The next operation is the most important one, however, and calls for the skill and consider able artistic knowledge of the retoucher. It is termed " modelling the face," and consists in bringing the high lights, semi-tones and deep shadows into harmony with each other in accord ance with the artistic laws governing light and shade.
Retouching machines have been constructed. They work by electricity. The pencil is given a peculiar movement which takes the place of the stippling. A machine of this kind is shown in Fig. 386.
The art of retouching is one that requires to be learned under the guide of a competent teacher. The principal thing is to know, on examining an untouched negative, what to do, and what not to do. Many make the great mistake of over-retouching, removing all individuality from the portrait.
Always make a print from the negative to act as a guide during retouching. On the subject of retouching, H. P. Robinson says :* "A very little unskilful retouching will remove the texture of the flesh and leave that of stone ; will remove the expression of a living face, and leave that of a mask ; whilst the same amount of retouching applied with knowledge and intelligence would have retained the texture of the flesh, removing only the temporary and accidental blemishes and the exaggerations of pho tography which interfered with truth and beauty ; would have given fuller effect to a fine expres sion or subdued a suspicion of frowning or weariness by delicate touches applied in the right place To know when to leave off should be the aim of the retoucher."
Chemical principle of this method* consists in arresting the action of the developer on the parts of the negative which come up too rapidly. For this purpose, as soon as it is ap parent that these portions are almost fully developed, the negative is removed from the developer, allowed to drain a moment, until there is no free liquid on its surface. Then all the portions where the detail is sufficient are painted by means of a camel-hair brush with a 5 per cent. solution of bromide of potassium. The gelatine absorbs this solution very rapidly, and the places may be gone over several times according as the detail is more or less out. The negative is then returned to the developer, and the development con tinued until the detail comes up in all portions of the negative. The development is nearly or quite arrested wherever the bromide was applied, and these portions do not gain in density. In the end a negative is ob tained with detail throughout.