CRACKED NEGATIVES Negatives are easily cracked if cheap frames with uneven beds and imperfect springs are used. The crack may at first appear slight and unimportant, but in time it invariably extends across the plate. With care the film on a cracked negative need not be broken ; merely bind the negative to a piece of glass of the same size by means of gummed strips of paper, or cement it bodily to the glass by means of a mixture of Canada balsam and benzole or xylol, the crack being first of all filled in with the mixture.
Many workers duplicate cracked negatives in the following manner. First paint on the glass side and along the crack a fine line of Brunswick black or other opaque varnish, and then make a positive transparency, on which, of course, the crack will be represented by a thin white line. Then, by means of a retouching pencil or a camel-hair pencil and suitable medium, retouch the white line, and make a negative from the transparency. Much depends upon the position of the line and the degree of skill exercised.
There are two systems of taking a print from a cracked negative without the crack showing, but the work must be done in daylight. One is to place the frame on a board attached to strings A, and to keep the board swinging or rotating in the shade while the picture is being printed. Another is to place the frame at the bottom of a deep box B, also in the shade. These methods are rather slow, but they give the best results possible with cracked negatives.
It is, of course, possible to remove an unbroken gelatine film from a cracked glass, and one of the best methods of doing so is the following : Carefully clean a sheet of glass one size larger than the negative to be treated, place the cracked negative, film side upwards, upon it, and coat evenly with enamel collodion.
Put on as much as the film will hold without its running over, allow to set thoroughly, and wash till the water runs freely off it ; drain, and coat with a solution of 20 grs. of gelatine in 1 oz.
of warm water, and allow to set thoroughly. Then immerse the cracked negative with its prepared film in this mixture : Hydrofluoric acid . 6o drops 6 ccs.
Glycerine r oz. 5o „ Alcohol 5o „ Water to . . 20 „ 1,000 „ In a few minutes the film will be free at the edges, and it should then be carefully coaxed off the glass by means of a camel-hair brush and trans ferred to a dish of cold water. Slip under the released film a sheet of glass coated with gela tine solution made as already stated ; or use an unexposed dry plate that has been fixed and washed. Coax out any wrinkles with the camel hair brush or by blowing, and allow to dry in a horizontal position. If the cracked negative has been varnished, all traces of the varnish must be removed before any attempt is made to remove the film. (See " Varnish, Removal of.") It is possible to do without the collodion, and so simplify the work of transferring the film, but greater care will be necessary. Immerse the negative in 12 oz. of water to which 6o drops of hydrofluoric acid have been added, and after the film becomes loose at the edges, coax it off very gently in the manner already described. Wash for about ten minutes, at the end of which time the film will be enlarged considerably ; if required it can be left in the enlarged state, but otherwise it must be immersed in a solution of equal parts of water and methylated spirit until it has contracted to its original size. Then float it upon a gelatine plate as above described.
In the case of a cracked new negative the film may be removed by soaking for about thirty six hours in a cold saturated solution of common washing soda ; all the after operations are as described in the preceding paragraph.
Cracked negatives other than gelatine are best treated as broken negatives (which see).