144 COCOA AND CHOCOLATE 



of polished chilled cast iron. Chilled cast iron rolls 

 have the advantage that they can be kept cool by having 

 water flowing through them. A skilled operator is 

 required to set the rolls in order that they may give a 

 large and satisfactory output. The cylinders in contact 

 run at different speeds, and, as will be seen in the 

 diagram, the chocolate always clings to the roll which 

 is revolving with the greater velocity, and is delivered 

 from the rolls either as a curtain of chocolate or as a 

 spray of chocolate powder. It is very striking to see the 

 soft chocolate-coloured dough become, after merely 

 passing between the rolls, a dry powder the explan- 

 ation is that the sugar having been more finely crushed 

 now requires a greater quantity of cacao butter to lubri- 

 cate it before the mixture can again become plastic. 

 The chocolate in its various stages of manufacture, 

 should be kept warm or it will solidify and much time 

 and heat (and possibly temper) will be absorbed in 

 remelting it ; for this and other reasons most chocolate 

 factories have a number of hot rooms, in which the 

 chocolate is stored whilst waiting to pass on to the 

 next operation. The dry powder coming from the rolls 

 is either taken to a hot room, or at once mixed in a 

 warm melangeur, where curiously enough the whole 

 becomes once again of the consistency of dough. The 

 grinding between the rolls and the mixing in the 

 melangeur are repeated any number of times until the 

 chocolate is of the desired fineness. Whilst there are a 

 few people who like the clean, hard feel of sugar crys- 

 tals between the teeth, the present-day taste is all for 

 very smooth and highly refined chocolate ; hence the 

 grinding operation is one of the most important in the 

 factory, and is checked at the works at Bourn ville by 

 measuring with a microscope the size of the particles. 

 The cost of fine grinding is considerable, for whilst 

 the first breaking down of the cacao nibs and sugar 

 crystals is comparatively easy, it is found that as the 

 particles of chocolate get finer the cost of further re- 

 duction increases by leaps and bounds. The chocolate 



