472 



this report. Much of my time was spent in acquiring knowledge 

 of these details in the various factories I visited. Three facts must 

 be remembered in order to properly understand the final manufac- 

 ture of rubber goods. The dough of masticated rubber, mixed with 

 sulphur and other ingredients, is plastic and has lost the original 

 elasticity of rubber. It can be cut and moulded, stamped into 

 shapes, bent and twisted, just as putty, clay, or a dough of flour 

 and water may. Rubber dough and masticated rubber are self 

 adhesive, and cut surfaces can be joined firmly together by simple 

 pressure, and if the surfaces be brushed over with benzole the pres- 

 sure required to form a very firm junction is of the slightest. On 

 heating the dough and masticated rubber which contains sulphur, 

 a chemical change takes place and a chemical compound of rubber 

 and sulphur is formed which possesses the original elasticity and 

 toughness of the raw rubber, but in a greater and more perfect 

 degree. This chemical change is called vulcanisation of the rub- 

 ber, and it is the final process to which practically all manufactured 

 rubber goods are put. It must never be forgotten that raw rubber 

 and vulcanised rubber are quite different and distinct substances, 

 their chemical compositions are different, their properties both 

 physical and chemical are quite distinct, and moreover though the 

 change from raw rubber to the sulphur compound of rubber — that 

 is, vulcanised rubber — can be easily effected by simple mixing and 

 heating to 300 F., the reverse process of removing the sulphur and 

 reforming raw rubber has never yet been done. 



27. The vulcanised rubber goods which the manufacturer 

 turns out may be divided into three main classes — I, stamped and 

 moulded goods; II, goods built up of rubber dough and other 

 material ; and III, sheeted and spread rubber goods. 



Stamped Goods. 



28. All solid rubber articles — such as heel pads, soles for shoes, 

 vulcanite stoppers, rubber rings, washers, mats, buffers and rubber 

 pads, billiard cushions, rubber tube, etc., — are prepared direct from 

 the dough by stamping them out by hand or by machines, coating 

 them with french chalk to prevent adhesion, and then vulcanising 

 simply by heating on trays or in iron moulds. The variety of 

 goods of this kind is enormous and without limit, and doughs of 

 most diverse composition from pure rubber and sulphur to mixtures 

 where rubber is present in very small proportion, are used for this 

 kind of work. This branch of the manufacture of rubber goods is 

 as simple to understand as the art of the pastry cook, who stamps 

 out fancifully shaped little cakes, or twists up curly bread, dredges 

 with flour and bakes in an oven. The secrets are in the recipes for 

 the dough, and the art in the manner of making the shapes and 

 regulating the baking. There are many ingenious and complicated 

 machines used to save labour, but some of the simplest articles no 

 machine can yet produce, and hand labour has to be employed. 

 Rubber rings of circular cross section, commonly called " umbrella 

 rings," have all to be made up by hand. If stamped or moulded 

 the strength is not to be relied upon. The mode of making is 



