COLOR PHOTOGRAPHY 641 



If trays are used, however, each film must be placed separately in a fresh bleaching 

 solution. The quantity of working bleach solution recommended is 8 oz. for an 

 8- by 10-in. tray. The three films must be evenly rocked during the bleaching opera- 

 tion to avoid streaky effects. The bleaching solution should be discarded immediately 

 after use. 



Hot-water Development. — The bleached films should now be placed in a tank of hot 

 water at 110°F. and the hangers lifted out of the tank and replaced in it about every 

 10 sec. This is to allow the melted emulsion to be drained away from the films. In 

 carrying out this operation, the greatest possible attention must be paid to prevent 

 the films from rubbing against each other as the relief image at this time is extremely 

 delicate. It is advisable to change into a clean tank of hot water again at 110°F. 

 after 1 min., continuing the agitation. After about 3 min., the film should be given 

 another rise in clean hot water; it can then be passed again into the fixing-bath formula 

 F-5. One minute in a fixing bath will be sufficient, after which the films can be put 

 to wash for about 5 min. in cold running water. If the hot-water development of the 

 films is carried out in trays, each film must be handled separately and the hot water 

 changed two or three times, but in any case the hot water should never be poured over 

 the film. Three of four changes of hot water for each tray will be sufficient, after which 

 the films will be passed into a fixing bath and washed. 



A faint trace of brown image remains in the relief film after treatment in a fixing 

 bath. This can be completely disregarded when the relief images are used to print 

 by dye transfer on paper. When making transparencies, however, it might be further 

 desirable to remove such a residual image by treating in a permanganate reducer 

 formula (R-2), followed by fixation in formula F-5 and additional wash. 



It is advisable to dry the relief images before staining in the appropriate dye baths. 

 Treatment in the Dye Solutions. — The three dye solutions are made up in accordance 

 with the instructions attached to each dye container, and in order to increase the 

 keeping qualities of the dye it is advisable to add 5 cc. of formalin to each 500 cc. of 

 dye solution. Each dye has placed in it a certain amount of 5 per cent acetic acid, 

 the amount controlling the amount of dye taken up by the matrix. Thus the color 

 contrast may be controlled. The amounts of acid are of the order of 5 to 20 cc. 



It is also best to filter the dye solution through rapid filtering paper 

 before use. 



Each relief film is now put in its appropriate dye bath for about 30 minutes at 

 68°F. and the tray occasionally rocked. The dyed relief films, when removed from 

 the dye baths, should be rinsed in two changes of 3^2 per cent solution of acetic acid and 

 distilled water. After this rinsing the three films can be placed in a tray containing 

 ^2 per cent of acetic acid until ready for the dye transfer. 



At this stage, the three stained reliefs can be superimposed to judge the color bal- 

 ance — this is best done on the bottom of a white porcelain tray — and examined in 

 strong white light, after which they can be returned to the tray containing }i per cent 

 solution of acetic acid or dried, the transfer process taking place at another time. 



Preparation of a Transfer Paper. — The transfer of the dyes can be made on any 

 ordinary type of bromide paper fixed in a fresh fixing bath (formula F-24) or the 

 especially prepared paper called imbibition paper. 



The paper must be first prepared by treating it for 5 min. in a mordanting solution 

 (formula M-1). This treatment should be followed by a wash for 5 min. in running 

 water and then by a treatment, also for 5 min., in a buffer solution consisting of a 

 5 per cent solution of sodium acetate. Finally the paper should be washed again 

 for another 5 min. 



Several papers can be treated at the same time and put away to dry for future use. 

 A transfer paper, which has been previously treated and dried, should be given a 



