COOLING AND DRYING 257 



and in some factories the most elaborate precautions are 

 taken for cleansing vessels, tools, floors, etc., and even for 

 their disinfection and sterilization. Iron, tinned iron, and 

 copper cooling vessels are ruled out on account of their 

 tendency to rust and tarnish, and the last is unjustifiably 

 expensive. Many of these vessels are unsuitable for pure 

 food gelatines in which traces of copper, zinc and arsenic 

 are held to be very objectionable. For the best gelatines, 

 therefore, a very shallow vessel (J* to J" deep) with a sheet 

 glass bottom is preferred, and the concentrated sol is run on 

 to this for gelation. 



Glue (or gelatine) which has set in this way is some- 

 times called " cast glue." That which sets in metal boxes 

 in blocks is termed " cut glue," because the blocks of jelly 

 need subsequently to be cut into slabs of the desired size 

 and shape. Jelly blocks may be cut by hand with the 

 " wire knife " which yields a characteristic wavy appear- 

 ance to the finished product. This may also be done by 

 machinery, the block of gel being placed on a series of 

 correctly spaced wires and forced through the network by 

 hydraulic pressure. A cutting machine (Schneible) has also 

 been used to cut up blocks of jelly into slices of the required 

 thickness, but these machines have not made great headway 

 in this country. It will be clear that cast glue is cooled more 

 rapidly than glue in blocks ; it is therefore not surprising 

 to note Lambert's statement that the former comprises the 

 larger proportion on the market. 



The cut or cast cakes are next placed upon network 

 frames, and a series of such frames are placed on a bogey. 

 The bogey is run along tram lines into the drying tunnel, 

 through which air is forced or induced by a fan. Many such 

 bogeys are, of course, passed into each tunnel, and as many 

 tunnels as required may be constructed. Care is necessary 

 to expose the cakes evenly to the action of the air. It is 

 mostly necessary to warm the air at the inlet by means of 

 steam pipes and so increase its drying power. This is 

 especially necessary in winter or wet weather. In summer, 

 however, it is often arranged that the air is cooled before 

 E. 17 



