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ON A VOLTAIC PROCESS FOR ETCHING 

 DAGUERREOTYPE PLATES. 



From the Proceedings of the London Electrical Society, Part II. ; having been 

 read before the Society on August 17, 1841. 



DR. BERRES, of Vienna, was the first, I believe, who pub- 

 lished a process for etching Daguerreotypes : his method was 

 to cover the plates with a solution of gum-arabic, and then to 

 immerse them in nitric acid of a certain strength. I have not 

 seen any plates thus prepared, but the few experiments which 

 I have made with nitric acid have given me a burred and im- 

 perfect outline ; and I have experienced extreme difficulty of 

 manipulation from the circumstance of the acid never attack- 

 ing the plate uniformly and simultaneously. My object, how- 

 ever, in this communication, is not to find fault with a process 

 which I have never perhaps fairly tried or seen tried by 

 experienced hands, and the inventor of which deserves the 

 gratitude of all interested in physical science ; but to make 

 public another, which possesses the advantage of extreme 

 simplicity, which anyone, however unskilled in chemical 

 manipulation, may practise with success, and which produces 

 a perfect etching of the original image ; so much so, that a 

 plate thus etched can scarcely be distinguished from an actual 

 Daguerreotype, preserving all the microscopic delicacy of the 

 finest parts of the impression. 



One sentence will, convey the secret of this process ; it 

 is to make the Daguerreotype the anode* of a voltaic com- 

 bination, in a solution which will not of itself attack either 

 silver or mercury, but of which, when electrolysed, the anion 

 will attack these metals unequally. This idea occurred to me 

 soon after the publication of Daguerre's process ; but, being 

 then in the country, and unable to procure any plates, \ 



* Strictly speaking this is a misapplication of Faraday's term : he applied jt 

 to the surface of the electrolyte ; as, however, all Continental and many English 

 writers (among whom I may name Whewell) have applied it to the positive electrode, 

 and as an expression is most needed for that, I have not hesitated so to apply it. 



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