MAKING MOULDS AND CASTS. 26? 



place, resting 1 on these nail-heads, and then put on the upper 

 half of the " jacket." Cord the jacket tightly together without 

 disturbing the position of the object inside. If there are any 

 cracks at the edges, fill them up with clay. Now pour in the 

 hot gelatine at the funnel-shaped hole in the upper half of the 

 jacket, until the mould is quite full. Let the mould stand two 

 hours to cool and harden ; then remove the upper half of the 

 " jacket." To get the object out, take a sharp knife and slit the 

 coating- of gelatine fully half -way round, so that the two halves 

 can be opened like an oyster, and the object lifted out. The 

 inside of the gelatine mould must now have a coating- to make 

 it impervious to the water in the plaster Paris. 

 Mix up the following : 



1 teacupful of spirits of turpentine. 

 About 4 level teaspoonf uls of white lead. 

 About 1 teaspoonful of lightning dryer. 



Mix this well, paint the inside of the mould with it, two coats, which makes the gela- 

 tine waterproof. 



To make a cast, oil the inside of the mould with lard oil, put 

 the plaster jacket around it, so that it fits perfectly, and tie the 

 two pieces of the jacket firmly together to prevent a disaster 

 when the plaster begins to heat in the mould. 



Mix your plaster with ice-water for the same reason, and you 

 will have no trouble. For irregular objects, the working of a 

 gelatine mould is perfection itself. It yields gracefully in com- 

 ing- out of the undercuts and around corners, takes every detail 

 perfectly, and in the jacket its shape is always the same. A 

 careful operator can make from twenty to fifty copies of a 

 cast in a single mould before its loss of sharpness necessitates 

 its abandonment. 



