58 ELECTROTYPE PROCESSES. 



moulds, and called by them lacquer. It is prepared in the following 

 manner: half-a-pound of soft soap is put into three pints of clean 

 water, which is set on a clear fire, and is kept in agitation by 

 stirring ; when it begins to boil, add from one ounce to an ounce 

 and a-half of tallow : the whole is then kept boiling till it is reduced 

 in bulk to about two pints, when it is ready for use. The surface 

 of the medal must be washed over with this lacquer, allowing it to 

 absorb as much as it can, when it assumes the appearance of polished 

 marble : it is now prepared with a rim of paper, and the mould 

 taken as directed for taking plaster moulds from metallic medals. 

 When hardened, they will separate easily. Wetting the plaster 

 model with a solution of soap before taking the cast will do, or, if 

 the plaster model has been saturated with oil or milk, it has only to 

 be moistened with sweet oil the same as a metal model. 



Fusible Alloy from piaster. If a mould of fusible metal be re- 

 quired from a plaster medal, the plaster may be saturated either 

 with boiled oil or the soap and tallow lacquer, and the mould taken 

 in the same manner as from a metallic medal. 



Copper Moulds from Plaster. Many electro -metallurgists prefer 

 taking a mould in copper when the medal is of plaster of Paris. 

 This is done by the electrotype process : the plaster model is satu- 

 rated with wax over a slow fire, as already detailed, and then pre- 

 pared for taking an electrotype in the usual manner (see page 48). 

 We need hardly mention that the model in this case is destroyed ; 

 but, notwithstanding, in the case of plaster models, to take a copper 

 mould is the most preferable, as it may be repaired in case of slight 

 defect, and it may be used over and over again without deterioration. 



When an electrotype is required of a model that is undercut, or 

 of a bust or figure, the process which we have described will not 

 answer, as the mould cannot separate from the model. In such 

 circumstances, the general method of proceeding is to part the 

 mould in separate pieces, and then join these together. The 

 material used for this purpose is plaster of Paris ; the operation, 

 however, to be done well, requires a person of considerable 

 experience. 



Elastic moulding. The process recently patented by Mr. Parkes, 

 for taking a mould of any kind of model in one piece, is excellently 

 adapted for the electrotypist. The material is composed of glue and 

 treacle : 1 2 Ibs. of glue is steeped for several hours in as much water 

 as will moisten it thoroughly. This is put into a metallic vessel, 

 which is placed in boiling water, as a hot bath. When the glue falls 

 into a fluid state, 3 Ibs. of treacle are added, and the whole is well 

 mixed by stirring. Suppose, now, that the mould of a small bust is 

 wanted, a cylindrical vessel is chosen, so deep that the bust may 

 stand in it an inch or so under the edge. The inside of this vessel is 



