MOULDING, 171 



The expansion of the air and gases, which are unavoidably 

 within the mass, will shape the article to conform to the mould. 



When hollow ware of any kind is formed, sheets of elastic 

 compound, artificial ivory, or fibrous fabrics, of the required 

 thickness, are cut in two or more pieces, with a knife, punch, 

 or dye, the edges of the pieces are either lapped, or butted 

 and cemented together, barely strong enough, so that the ar- 

 ticle may be partially filled with air before it is put into the 

 mould. By the expansion of the air and gases, while the article 

 is vulcanizing, it is caused to fill the mould completely, even to 

 the finest line engraved upon it, and having assumed, it retains, 

 when vulcanized, the form and shape of the mould. The average 

 thickness of the article being a little less than the sheet of gum 

 used for it. 



When an article is made from more than two pieces of the 

 sheets of any considerable thickness, say one-eighth of an inch 

 or more, it is not necessary that they should be inflated at all 

 with air, as they will necessarily inclose enough to shape the ar- 

 ticle to the mould. It is not necessary that the pieces, when 

 cemented together, should have any particular resemblance to 

 the article which is to be moulded. The same pieces, which are 

 cut in halves and inflated, or in four quarters, like the peel taken 

 from an orange and not inflated, (the edges being butted to- 

 gether,) will make a bird, or a doll's head, as well as a bat ball. 

 In other words, angular and divers shaped articles may be made 

 from the same pieces as spherical and smooth ones. Tumblers, 

 dishes, cups, &c., may be formed in this way, in united pairs from 

 similar formed pieces ; and when cut apart, after being vulcan- 

 ized, two articles are obtained from one mould by each process 

 of filling it. 



Shoes or pitchers may be formed from the same or similar 

 shaped pieces, space being left in the mould where the top or 

 mouth of the article is formed, which leaves a comb or spur on 

 the article ; this being cut off, the article becomes opened and 

 finished. 



This method, which was first applied to the manufacture of 



