462 HANDBOOK OF PHOTOGRAPHY 



Ferrocyanide Toners. — Ferrocyanide compounds of other metals than silver have 

 various and brilliant colors and may be substituted for the silver image. Iron com- 

 pounds are blue; uranium, brownish red and brown; copper, red, etc. 



Ordinarily the silver image is first converted into silver ferrocyanide, and this is 

 subsequently converted into the desired metallic compound by direct replacement of 

 the silver by the metal of the ferrocyanide compounds. Usually other organic con- 

 stituents are added to the formula to restrain the action of the toners, to prevent 

 stains, etc. Most toning formulas of this class are similar in their reactions, although 

 some of the single solution formulas form the silver ferrocyanide and the metallic 

 ferrocyanide in one operation. Others involve two operations, first the conversion 

 of the black silver image into silver ferrocyanide and subsequently the replacement 

 of the silver in the silver ferrocyanide by the suitable metal higher in the electromotive 

 series. The formulas we give may be considered representative of this type of toner. 



Toners of this class are more susceptible to troubles caused by impurities and by 

 deviations from recommended procedures than any of the others and therefore require 

 considerably more care in their use. Also many of these metallic ferrocyanide com- 

 pounds are soluble in even mild alkalies, and therefore water which is slightly alkaUne 

 when used in washing might remove some of the image. The use of these toners 

 generally requires considerable care and experimentation in order to produce the 

 desired results. 



Copper Toner. — This toner hesitates for a moment, then a distinct toning action is 

 noticed which proceeds quite rapidly at first. The tone goes from a cold brown, 

 toward red, during which time a double tone, brown and red, is formed. After this 

 the toning is progressive to red. The success in obtaining the desired tone by this 

 method rests in the control of the time of toning and being able to judge just when the 

 desired tone is reached. When using a toner of this type, it is wise to make several 

 prints, toning them for different lengths of time with constant temperature, so that 

 when the prints are dried one has several different tones from which to select. By 

 this time method one may duplicate tones when prints in quantity are being processed. 

 Toning solutions are as follows: 



Solution A 



Copper sulphate (cupric) 4 g. 60 gr. 



Potassium citrate 16 g. 240 gr . 



Water to make 600 cc. 20 oz. 



Solution B 



Potassium ferricyanide 3 . 5 g. 50 gr. 



Potassium citrate 16 g. 240 gr. 



Water to make 600 cc. 20 oz. 



To use, mix equal parts of A and B and tone the black-and-white print in this solution. 

 Iron Toner. — The following toner will produce blue tones. Tone in following bath 

 until desired color is obtained. 



Iron and ammonium citrate (ferric) (10 per cent) 60 cc. 2 oz. 



Potassium ferricyanide (10 per cent) 60 cc. 2 oz 



Acetic acid (10 per cent) 600 cc. 20 oz. 



Wash in pure water, but not too long, as blue color is soluble in water even slightly 

 alkaline. 



Uranium Toner. — Uranium toner yields shades from black through brown to a 

 yellowish red. While this toner, in some instances and for certain effects gives satis- 

 factory tones, the writers have never had very good results with it. It is included 

 here for those workers who seek the unusual and bizarre. 



Prints should be toned in the following solution after they have been thoroughly 

 washed. 



