AMATEUR PHOTOGRAPHY 



197 



as the instances in which they suit the sub- 

 ject rarely occur in lantern slide work. 



The following formula may be used when 

 a sulphocyanide toning bath is wanted : 



Ammonium sulphocyanide 60 grains 



Gold tri-chloride 5 



Water 16 ounces 



The gold should be dissolved in .half the 

 quantity of water, and the sulphocyanide 

 in the remaining half, the solution of gold 

 being added slowly to the sulphocyanide so- 

 lution, stirring this all the time. Some 

 form of platinum bath is a good agent for 

 lantern slides, though a mixture of gold 

 and platinum behaves even better. Potas- 

 sium chloro-platinite is the particular salt 

 recommended, and not platinum bichloride. 

 This latter salt is often nuite acid with 

 hydrochloric acid, and requires neutralizing 

 first with some alkali and then reacidifying 

 with nitric acid. If potassium chloro-plat- 

 inite is used, no trouble will be experienced. 



The formulae usually given for platinum 

 toning baths are too weak, requiring an 

 inconveniently long time before any marked 

 change is effected. The following bath is 

 much more concentrated than usually rec- 

 ommended, but gives good results in my 

 hands : 



Potassium chloro-platinite 5 grains 



Gold tri-chloride 5 " 



Hydrochloric acid 10 minims 



Water 5 ounces 



Platinum toning, if carried far, intensi- 

 fies the image slightly, so that should an 

 attempt be made to tone a red slide quite 

 black the slide might be found worthless on 

 drying,' from the adventitious opacity ac- 

 quired in toning. The most suitable slide 

 for toning is one devoid of large shadow 

 masses, and one which needs additional 

 density to make it a perfect slide. 



The following modification of the gold 

 platinum bath is convenient, as with it the 

 increase of density is scarcely noticeable : 



Sodium phosphate 50 grains 



Gold trichloride 5 " 



Potassium chloro-platinite 5 



Water S ounces 



t 



This bath must be used fresh, and will 

 not keep. Toning with it is rapid, but a 

 pure black is not readily procurable. 



Toning slides from black to warm is less 

 easy than the foregoing, besides the alter- 

 ation of color. Copper toning appears to 

 give better results than uranium, as the 

 staining of the gelatine previously referred 

 to when speaking of uranium toning does 

 not take place. A 10 per cent solution of 

 copper sulphate, potassium ferricyanide, and 

 neutral potassium citrate is recommended. 

 To prepare toning bath take : < . 



Cupric sulphate 10% solution. .140 minims 



Potassium ferricyanide, 10% so- 

 lution 120 " 



Potassium citrate, neutral, 10% 



solution 4 ounces 



Add the potassium citrate to the copper 

 sulphate, and pour in the potassium ferri- 

 cyanide. A .clear green solution will result, 

 which keeps well and tones readily, with- 

 out staining, from purple black to red. 



Uranium is less satisfactory than copper, 

 owing to its liability to stain. As, however, 

 beautiful results can be obtained with care- 

 ful working by the process, I do not feel 

 justified in excluding it from notice. The 

 exact strength does not seem of much im- 

 portance, a stronger solution merely work- 

 ing quicker. The following is a convenient 

 strength : 



Potassium ferricyanide 5 grains. 



Uranium nitrate 5 



Acetic acid, glacial i l / 2 drams 



Water 2 ounces 



After toning, wash the slide in running 

 water about 10 minutes. Take care not to 

 wash too long; otherwise the brown color is 

 washed out, leaving the image unsatisfac- 

 tory. Uranium toned slides should be var- 

 nished when dry, to prevent fading, 



A pleasant bluish green color may be 

 given to a lantern slide that has been toned 

 brown with the uranium toning bath if it is 

 well washed and immersed in the following : 



Hydrochloric acid 20 minims 



Iron perchloride solution 10 



Water 5 ounces 



The color obtained is suitable for foliage 

 subjects, but as the gelatine is stained 

 throughout the slide any subjects with 

 masses of high lights do not look well. 

 The green color, however, can be dis- 

 charged from any portion of the slide by 

 treating it with a weak solution, say 20 per 

 cent, of ammonia. Thus, the sky portion, 

 where the stain shows more objectionable, 

 can be cleared. Again, a slide, having been 

 toned brown with uranium, can have cer- 

 tain portions of it toned green by applying 

 with a camel's-hair brush the iron solution 

 given previously. In this way a slide with 

 2 colors results, and some subjects look ef- 

 fective when done in this manner. 



In spite of the variety of results that can 

 be obtained by toning methods, I urge the 

 lantern slide worker to devote all his care 

 to gaining a high class slide by the process 

 of development. Reducing and intensifying 

 methods are of greater importance than 

 toning formulae. However expert and care- 

 ful one may be, a certain proportion of his 

 work will always be the better for read- 

 justment in one direction or the other. 

 Either some portion of the slide is over 



