56 ELECTROTYPE PROCESSES. 



hard. The impressions taken in this way are generally very fine ; 

 when the medal is not deep cut, a less pressure may suffice, but 

 when the pressure is too little the impression will be blunt. 



Gutta percha takes a coating of black lead readily, and the 

 deposit goes over it easily. 



moulds from Fern, Sea- Weed, &c. A method of taking impres- 

 sions of fern leaves and sea-weeds has recently been proposed by 

 Dr. F. Branson, in the Athenceum. It is thus described: 



" A piece of gutta percha, free from blemish, and the size of 

 the plate required, is placed in boiling water. When thoroughly 

 softened, it is taken out and laid flat upon a smooth metal plate, 

 and immediately dusted over with the finest bronze powder used 

 for printing gold letters. The object of this is threefold to dry 

 the surface, to render the surface more smooth, and to prevent 

 adhesion. The plant is then to be neatly laid out upon the bronze 

 surface, and covered with a polished metal plate, either of copper or 

 of German silver. The whole is then to be subjected to an amount 

 of pressure sufficient to imbed the upper plate in the gutta percha. 

 When the gutta percha is cold, the metal plate may be removed 

 and the fern gently withdrawn from its bed. A beautiful impres- 

 sion of the fern will remain." An electrotype may be deposited 

 upon the bronzed or black-leaded gutta percha. 



We have seen many electrotype leaves done by this method, 

 which were certainly very pretty as electrotypes, and the process 

 is well adapted for flat leaves ; but the pressure required renders 

 it unsuitable for some kinds of leaves, indeed it destroys the 

 natural forms of the greater number both of leaves and sea-weeds. 

 The products of the process cannot, indeed, be compared with those 

 electrotype leaves, the moulds of which are taken by wax. The 

 great merit of the process is its ease and simplicity. The method 

 given for taking the mould of the leaf is suitable for any kind of 

 flat mould in gutta percha. The mould of a leaf may be taken in 

 plaster, by placing the leaf upon dry sand and pressing the sand 

 under and on each side to fill up the spaces under the leaf, so as 

 to bear the pressure of the plaster, putting a collar of paper round 

 the sand to prevent its yielding, and then pouring the plaster over 

 the whole. When the plaster is set, the leaf is removed and the 

 plaster trimmed round with a knife. This also has its difficulties : 

 for when leaves have hairs upon them, they stick into the plaster. 

 The method of taking moulds of leaves in wax is by holding the 

 leaf in the hand, and brushing a thin layer of melted wax over the 

 surface to be moulded ; allowing this to harden, and then brushing 

 on another layer; and so on until the wax is sufficiently thick to 

 suffer handling. The leaf is then gently drawn off the wax, which 

 is to be black-leaded, and put into the electrotype, apparatus to 



