456 HANDBOOK OF PHOTOGRAPHY 



are permanent and will keep their tones indefinitely without fading. Siich toners 

 are easy to use, are economical, and can be depended upon to duplicate values fairly 

 well. 



The success of these methods depends upon the character of the original black-and- 

 white print. As a general rule maximum exposure and full development produce 

 prints which will tone well by these processes. Underexposure and overdevelopment 

 and the reverse, viz., overexposure and underdevelopment should be avoided in all 

 instances. A few trial prints made on the paper selected with varying times of 

 exposure and development, but all approximately the same density, will easily estab- 

 lish the correct procedure. Fresh solutions should always be used and care taken 

 that they are not overworked. The temperature of the developer should be kept as 

 near 70°F. as possible. Bromide in the developer used for the black-and-white prints 

 has quite an influence on the final results; i.e., slightly increasing the bromide content, 

 will yield somewhat warmer tones in the final print tone. 



The sulphide processes may be divided into two classifications. 



1. Direct sulphide process in which the silver image is changed directly to silver 

 sulphide with no intermediate steps. 



2. Indirect sulphide process in which the silver image is first changed to an insol- 

 uble silver salt or a mixture of silver and mercury salts which are then changed to the 

 sulphides of these metals. 



Direct Sepia Process. — The three most commonly used direct processes are hypo 

 alum, hypo-alum gold chloride and "liver of sulphur." As all these direct methods 

 have hypo as one of their ingredients, it is not necessary to wash the prints after 

 fixing, but they may be transferred directly to the toning bath. 



The chief disadvantage of these methods is that the solution must be used hot 

 (approximately 120°F.), and it is necessary to have some method of keeping this 

 temperature fairly constant. It takes from 15 to 60 min. to tone prints at this 

 temperature, depending on the kind of paper used. Toning in a cold solution would 

 require about 10 to 12 hr. Some photographers leave prints in these mixtures over- 

 night, but this is not good procedure and should be avoided. Another caution that is 

 very important is to use these toners in a separate room or at least at a distance from 

 any sensitized materials, such as paper or film, for direct sepia toners give off sulphur 

 fumes when heated which are destructive to sensitized materials. Good ventilation 

 is absolutely necessary. Abrupt changes of temperature should be avoided, prints 

 should be allowed to cool after being removed from the toning bath and before washing. 

 If this is not done, frilling and blistering will result. Prints should be sponged off 

 carefully after removal from the toning baths, to remove sediment; allowed to cool; 

 and then washed in cold running water for 15 to 20 min. 



Hypo-alum Sepia Method. — Two common photographic chemicals are used in this 

 formula, viz., hypo and potassium alum. When alum, which is acid, is added to a 

 solution of hypo (sodium thiosulphate), free sulphur is precipitated. This pre- 

 cipitated sulphur, when combined with the silver image of the print during toning, 

 forms brown silver sulphide. 



A silver "ripener" which retards the bleaching action due to the hypo must also be 

 added to the solution. Chloride, bromide, or iodide are used for this purpose. If 

 six or eight waste prints are at hand, it is possible by toning these prints to dispense 

 with the ripener, as the silver salts supplied by these prints will serve the same pur- 

 pose. The bath may be used indefinitelj' or until it is so reduced by evaporation that 

 it is necessary to replenish it, when a fresh solution must be added. 



Very definite instructions are given as to how these ingredients should be com- 

 bined in the bath, and anj^ deviation from this order will result in failure. It is 

 equally important to keep the solution at the temperature given, as too hot a bath 



