HAP. IX.] 



ELEGTRO-PLA TING. 



707 



as many stereotype plates for printing from as we may wish may be 

 reproduced in the following way. The surface of the wood is first 

 metallized by plumbago, and then an impression is taken with 

 gelatine or gutta-percha. The mould thus obtained and metallized is 

 submitted to the electro-plating process, and a layer of copper is 

 deposited on it, which reproduces with the greatest fidelity the finest 

 marks of the engraving at the end of a certain time, generally not 

 more than five hours. The thickness of the metal covering is about 

 vijih of a millimetre. This is not sufficient to offer proper resistance to 

 the action of the printing press, but it is strengthened by pouring 



FIG. 45(5. Reproduction of a Medal by electro-typing : intaglio Mould and Meda reproduced 



in relief. 



over the other side a mixture of lead and antimony (type metal). It 

 is then planed, and mounted on wood, and the stereotype plate thus 

 obtained is ready for working off. It can then produce without 

 spoiling or alteration an impression of eighty thousand examples 

 As to the wood engraving, it remains absolutely intact, and can furnish 

 an indefinite number of similar stereotype plates. 



An analogous process gives a reproduction of copper or steel 

 engravings. Ordinarily the cast is obtained by electro-typing, and this 

 mould is_used to reproduce the original plate. A precaution however 

 must be taken, in order to avoid adhesion, and this is done by expos- 



z z 2 



