29 

 SECOND PREPARATION. 



Note. I do not think it fit to allow a longer interval than twelve 

 hours to intervene between this operation and iodizing the plate. 



We left the plate with a deposit of gold and platinum. In 

 order to polish the metallic layer, the plate is rubbed with a piece 

 of cotton, and oil and rouge, until it again becomes black ; and then 

 with alcohol and cotton only, in order to remove this layer of 

 rouge as much as possible. 



The plate is then rubbed very strongly, and passing several 

 times over the same places, with cotton impregnated with cyanide. 

 As this layer dries very promptly, it might leave on the plate 

 traces cf inequality ; in order ttr avoid this, the cyanide must be 

 again passed over it, and, while the plate is still moist, we quickly 

 rub over the whole surface of the plate with cotton imbibed with a 

 little oil, thus mixing these two substances ; then, with a piece of 

 dry cotton, we rub in order to unite, and at the same time, to dry 

 the plate, taking care to remove from the cotton the parts which 

 are moistened with cyanide and oil. Finally, as the cotton still 

 leaves traces, the plate is likewise sprinkled with a little rouge, 

 which is removed by gently rubbing. 



Afterwards, the plate is again rubbed with cotton impregnated 

 with oil, only in such a manner as to make the burnish of the metal 

 return ; it is then sprinkled with rouge, and then very gently 

 rubbed round, in such a manner as to remove all the rouge, which 

 carries with it the superabundance of the acidulated layer. 



Finally, it is strongly rubbed with a rather firm pledget of cot- 

 ton, in order to give the best polish. 



It is not necessary often to renew the pledgets of cotton imbibed 

 with oil and rouge ; they must only be kept free from dust. I 

 have said above, that the first preparation of the plate may serve 

 indefinitely ; but it will be comprehended, that the second must 

 be modified, according to whether we operate on a plate which has 

 received a fixed or an unfixed impression. 



ON THE FIXED IMPRESSION. 



The stains left by the washing-water, must be removed with 

 rouge and water, slightly acidulated with nitric acid (at 36 F. at 

 this season [April?] and less in summer.) 



Afterwards, the plate must be polished with oil and rouge, in 

 order to remove all traces of the image. 



