THE PRODUCTION OF POSITIVES, ETC. 139 



brown verging on purple gives the most artistic ap- 

 pearance when finished. Should an engraving tone 

 be required the process must be continued until a 

 decided purple tint is produced. Overtoning is to 

 be avoided as a cold grey picture is the result. 



After toning the washings are repeated and the 

 prints finally fixed in a solution containing — 

 Sodium Hyposluphite, 1 is. 

 Liq. Ammon. Fort, itj, iii. 

 Water, | ix. 



This solution should not be above 85° or below 75° 

 Far. and always freshly made. 



After ten or fifteen minutes immersion, with con- 

 tinual motion, the unaltered silver will be dissolved 

 away. The prints are then immediately removed to 

 a large tub of water, and kept in continual motion 

 for a quarter of an hour. The water is then 

 changed ; at the end of an hour the change re- 

 peated ; at two hours again repeated, and so on for 

 eight hours. At the expiration of this time all 

 traces of hypo will have disappeared ; the prints are 

 then hung up to dry. 



All these operations, except the final washings 

 must be conducted in a subdued light, coloured light 

 will not answer, white light alone enabling us to 

 distinguish the proper tint when toning. The prints 

 when dry are cut to the required shape, with a sharp 

 knife, not scissors, and mounted on cardboard with 

 thick starch or glue, to which a few drops of carbolic 

 acid have been added. When perfectly dry their ap- 

 pearance may be much improved, by passing through 



