PRECAUTIONS ON PUTTING THE MOULDS INTO THE SOLUTIONS. 61 



thick for removing which, in ordinary circumstances, will require 

 from two to three days the medal is taken out of the solution, and 

 washed in cold water, and the connection is taken off. If the deposit 

 has not gone far over the edge of the mould, the two may be separated 

 by a gentle pull ; if otherwise, the superfluous deposit must be eased 

 off and if care be taken, the wax may be fit to use over again : but 

 when the mould is plaster of Paris, however well it may be saturated 

 with wax, it is seldom in a condition to use again. If the plaster 

 mould be large and thick, it is advisable to coat the back with wax 

 or tallow, which is done by brushing it over with either substance 

 in a melted state : the mould being cold will not absorb the wax or 

 tallow ; hence it may be recovered again. The sulphate of copper 

 possesses so penetrating a quality that if the slightest imperfection 

 occurs in the saturation of the mould by wax, the solution will pene- 

 trate through it, and the copper will be deposited upon the face of 

 the object, giving it a rough, matted appearance, and seriously 

 injuring it. 



Using metal Moulds. The mould in fusible alloy does not require 

 to be black-leaded, but the back and edge must be protected by a 

 coating of wax or other non-conducting material ; it may be con- 

 nected in the same way as the penny-piece (page 48) by putting a 

 wire round its edge previous to laying on the non-conducting sub- 

 stance, such as tallow or wax, which should also cover the wire. 

 Or a slip of copper, or wire, may be laid upon the back and fastened 

 by a drop or two of sealing-wax ; the back is then coated : but care 

 must be taken that the wax do not get between the connection and 

 the medal which will prevent deposit. The deposit on this mould 

 goes on instantaneously, the same as over the penny-piece. When 

 sufficiently thick, it may be taken off in the same manner as from 

 the wax mould, the surface having been prepared by turpentine 

 (page 48) to prevent adherence. These moulds may be used several 

 times, if care be taken not to heat them, as they easily melt. 



The medals obtained from metallic moulds prepared with the 

 turpentine solution have a bright surface, which is not liable to 

 change easily, but if the mould has been prepared with oil or com- 

 posed of wax or plaster, the metal will either be dark, or will very 

 easily tarnish. The means of preserving them, either by bronzing 

 or plating with other metals, will be detailed in a subsequent section. 



Precautions on putting the moulds into a Solution. In putting 

 moulds into the copper solution, the operator is often annoyed by 

 small globules of air adhering to the surface, which either prevent 

 the deposit taking place upon these parts, or, when they are very 

 minute, permit the deposit to grow over them causing small hollows 

 in the mould which give a very ugly appearance to the face of the 

 medal. To obviate this, give the mould, when newly put into the 



