MOULD OF PLASTER FROM PLASTER MODELS. 57 



receive the coating of copper. A type of the leaf is by this means 

 obtained with all its natural convolutions. 



Casting of Reptiles, &c. Imbed the subject in a mould made of 

 four parts of plaster of Paris, one of unburnt lime powder, and 

 one of Flanders brick-dust. Dry the mould carefully, then make it 

 red hot, and burn the subject out of it, taking care to free the mould 

 from the ashes. Fusible metal may be cast in this mould, and then 

 be covered with copper, from which the alloy may be afterwards 

 melted, or a wax model may be taken of the object, pouring the wax 

 in just before setting. In neither case must the mould be melted 

 until after the model, whether of alloy or wax, is taken, when the 

 whole is placed in water, the lime causes the mould to dissolve or 

 break up, and the figure modelled within it may be taken and 

 covered with copper. Flowers, insects, lizards, and other little animals 

 may be typed in this way. In all these processes, perseverance and 

 care are the best cures for little difficulties. 



Wax moulds from Plaster. If the object, which we assume to be 

 a medal, from which the mould is to be taken, be composed of plaster 

 of Paris, and the mould to be taken is in wax, the first operation is 

 to prepare the plaster medal. Some boiled linseed-oil, such as is 

 used by house-painters, is to be laid over the surface of the medal 

 with a camel's hair pencil, and continued until it is perfectly satur- 

 ated, which is known by the plaster ceasing to absorb any more of 

 the oil. This operation succeeds best when the medal is heated a 

 little. The medal should now be laid aside till the oil completely 

 dries, when the plaster will be found to be quite hard, and having 

 the appearance of polished marble: it is, consequently, fit to be used 

 for taking the wax mould, which is done in the same manner as we 

 have described for taking a wax mould from a metallic medal. 



Many prefer saturating the medal with water: this is best done 

 by placing the medal back down in the water, but not allowing it to 

 flow over the face; the water rises, by capillary attraction, to the 

 surface of the medal, rendering the face damp without being wet. 

 The rim being now tied on the plaster medal, the melted wax is 

 poured upon it. This method is equally good, but liability to 

 failures is much greater, caused generally by the wax being too hot. 



The plaster medal may also be saturated with skimmed milk, 

 and then dried ; by repeating this twice, the plaster assumes on the 

 surface an appearance like marble, and may be used for taking wax 

 moulds. 



Mould of Plaster from Plaster Models. When a plaster mould is to 

 be taken, the face of the model is - prepared differently to that de- 

 scribed, in order to prevent the adhesion of the two plasters. The 

 best substance we have tried for this purpose is a mixture of soft 

 soap and tallow, universally used by potters for preparing their 



