RETOUCHING 473. The Purpose of Retouching. As a rule, the term " retouching " (negative retouching) is used to describe work done on the gelatine of a negative with a pencil and scraper. Retouch ing corrects certain technical faults in negatives and, above all, faults of modelling. It is an almost universal rule in portrait photography to tone down or suppress wrinkles, freckles, and superfluous hair, to accentuate some lights and to lessen shadows which are too deep ; often to modify an expression, and sometimes even to change the form of the face.
No retouching is admissible on negatives whose interest is scientific, historical, or docu mentary.
As a matter of principle, retouching should never be employed to make up for faults if the opportunity is available to avoid them by making a new negative under better conditions.
The beginner must be patient and should practise as much as possible on waste negatives. He will save a great deal of time if he can arrange to take some lessons from a practised retoucher.
The amateur who wishes, in an exceptional case, to retouch one of his own pictures, will save time by making an enlargement, on which all corrections may be much more easily effected, then making from this enlargement a negative of the size required.
474. Retouching Appliances. The retouching desk, large and firm,' should be installed for preference near a north-light window, and at such a height that the retoucher may work seated before it without having to lean forward. Blinds must be arranged to screen both desk and worker from light at the sides and back. For work with artificial light it is often advan tageous to cover the usual minor with a sheet of white matt paper.
The scrapers should be of very good quality and very carefully sharpened ; one may use a surgeon's lancet, a vaccinating pen mounted in a solid penholder, or a large tailor's needle of which the point has been hammered and ground so as to obtain an edge formed by two surfaces inclined at about 45°, the needle then being fixed in a wooden handle, or mounted in the handle of an engraver's needle. A small oil
stone (Arkansas stone, white and translucent) is used for sharpening the scrapers ; the surface of this stone must be kept soaked with mineral oil. Sharpening is finished with a razor strop.
It has also been suggested (R. Demachy, 19o5) that engraving tools and the triangular scrapers used by engravers should be used for removing details or undesirable reflections from negatives. For local abrasion of the film, the use of a scraping brush of metal or glass wire has been recommended.
We must also note the use of stippling tools, which are very like pencil-cases. In the inside of one of these tools is a point which is actuated by a minute electric motor, either with a to and fro motion or with an eccentric circular motion.
The pencils for negative retouching are of the best-quality graphite, selected from the groups H, F, JIB, and 13, 1 or the bare leads of similar grades mounted in the corresponding pencil cases, inside which the leads may be completely covered in order to protect them when not in use. 2 Pencils should have long and very regular points : the wood is cut for a length of '1 in. or 2 in., care being taken not to break the lead. A little square of emery paper is then folded in two with the emery inside ; this is held between the thumb and first finger of the left hand, and the lead of the pencil is introduced into the fold and turned between the fingers of the right hand, at the same time giving it a to and fro movement.
Pencils will not as a rule mark bare gelatine or the varnishes generally employed to protect negatives; the surfaces must first be prepared 3 by means of a special varnish (retouching medium).
Retouching medium may be prepared by dissolving gum dammar in benzene, or, better, in a mixture of equal volumes of benzene and turpentine. The proportions are I to 2 oz. of gum to 20 oz. of the mixture, adding a few drops of oil of lavender or castor oil. Turpentine could also be left for a long time in a badly stoppered bottle, where it partially resinifies, (Inc to oxidation by the air.