COPPERING. 157 



Mr. Urquhart recommends as a coppering bath a solution of 

 cupric and potassic cyanide. 



"In order to easily prepare a bath," says he, " dissolve 900 

 grammes of potassic cyanide at 50 per cent, in 4 5 litres of 

 water ; add as much cupric cyanide as can be dissolved by the 

 liquid, then add about 113 grammes of free potassic cyanide." 



When it is desired to obtain thick deposits, it is necessary 

 to at first apply a film in a cyanide solution, take the object out, 

 wash it, and immediately dip it in the sulphate solution, when 

 it can be coated to any desired thickness. 



The American, French, and English formulae which we have 

 given are all good, and give satisfactory results. We, however, 

 believe that that of Mr. Watt is to be preferred to a certain ex- 

 tent in this respect, that it is more economical and gives a more 

 rapid deposition. 



COPPERING OF CAST AND WROUGHT IRON. 



OP THE IMPORTANCE OF THE INDUSTRY OF COPPERING ON 

 CAST IRON. The industry of artistic castings has made during 

 the last half century considerable progress, and particularly in 

 France, where it has succeeded in popularising the master works 

 of statuary, and in increasing, in a large proportion, the means 

 at the disposal of the architect for the ornamentation of our 

 modern dwelling-houses. 



Cast iron is easily melted, the mouldings are obtained with 

 a nicety of form, a precision of outline, a neatness in the details 

 which leave nothing to be desired. Unhappily oxidisation 

 rapidly destroys these precious qualities, and there really exists 

 no thoroughly effective remedy against this troublesome dis- 

 ease. 



The best known preservative is the painting with oil of the 

 object ; but although its application is simple and economical, it 

 must be admitted that it is not artistic, and that it requires 

 a considerable amount of maintenance. Coppering, on the 

 contrary, resists the action of time better, preserves the metallic 

 appearance of the pieces which is altered by the paint, and 

 when it is effected directly does not take away any of the 



