361. Frilling Of Edge Of Tissue During Development

Frilling Of Edge Of Tissue During Development. The tissue was left too long in the water before the transfer was made, or the superfluous moisture on the edge of the support was not blotted off after transfer.

362. Half- Tones Motley And Uneven

Half- Tones Motley And Uneven. If in the finest halftones there appear transparent or only partly opaque spots, generally round, of varying sizes, and not close together, there has been a crystallization of the bichromate solution, through the use of too strong a solution. The difficulty may also occur if the tissue is sensitized too long and followed by insufficient superficial drying of the solution. The remedy is to employ weaker sensitizing baths, and after sensitizing, clean blotting paper should be applied to the film, or the film drawn carefully over the edge of the sensitizing tray two or three times, in order to remove all excess solution. Two or three minutes sensitizing is sufficient.

363. Dark Spots Or Streaks On Prints

Dark Spots Or Streaks On Prints. This is caused by excess of bichromate solution and uneven drying, so that greater sensitiveness is produced in different places. Excess of sensitizer should be removed by drawing over the edge of the tray, squeegeeing the tissue on glass, or by blotting off the pigment surface.

364. Print Hard

Print Hard. The sensitizer is too weak or contains too much ammonia, or has been dried too quickly.

365. Print Flat

Print Flat. Sensitizer is too strong. For soft negatives a weak sensitizer of 1 to 3 per cent. should be used, with enough ammonia to turn it straw color. For hard negatives 4 to 5 per cent should be used, without ammonia.

366. Half- Tones Eaten Away

Half- Tones Eaten Away. Should the half-tones dissolve away quickly, yet the balance of the print appear fairly strong, the developing water is too hot, or too hot water was poured on the film. This difficulty is also caused by strong agitation of the water during development. The developing water seldom need exceed 85° to 100° Fahr. The print should be allowed to develop gradually and strong agitation avoided. If the difficulty occurs after having observed these precautions, the negative will require a paper sensitized with a strong solution.

367. Blisters

Blisters. Blisters are of two kinds-large and small. Those due to air on the surface or to air in the substance of the paper are usually small, but large blisters sometimes occur, so large and so numerous that almost half of the print will come away from the support. These may usually be traced to the tissue rather than to transfer paper; over-printing; printing in the sun or too near an arc lamp, so that the tissue becomes partially insoluble from the action of heat; stale tissue; tissue dried in a room with impure atmosphere; any of these produce surface insolubility and prevent satisfactory adhesion of tissue to the transfer paper, resulting in blisters.

368. Blisters will sometimes occur where there are large areas of heavy shadow, especially if the negative is too strong, and very full printing has been necessary to secure detail in the highlights. In the last instance the remedy is obvious-softer negatives must be produced and the existing negative either reduced with persulphate, or the shadows softened by the aid of stumping sauce applied to the back of the negative. In the other cases avoid heating the tissue during printing, and be careful to use only tissue which, before printing, is in a perfect condition of solubility. This point may be readily tested by slipping a bit of the tissue into water of 85° to 90° Fahr., when the gelatin should melt quite freely within a half minute. If it does not melt throw the tissue away. During the process of developing-in fact at all stages of the work-the tissue should not be subjected to sudden changes of temperature, as placing the tissue first in a cold bath and then in a warm one, or vice versa, will invariably cause blisters, and sometimes reticulation.