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long, which is rapidly oscillating with a saw-like movement and 
which is well lubricated with water or soap and water. Sheets cut 
in this way show a fine striation due to the little ridges which mark 
the progress of the knife at each stroke across the block or cylinder. 
A good tobacco pouch is usually made from this cut-sheet and 
shows the appearance described. The most interesting feature in 
making cut-thread or sheet to the man interested in rubber is the 
process of preparation of the rubber into blocks ready for the knife. 
The utmost care must be taken in the preliminary washing, and if 
any grit be in the raw rubber the washed sheet is subjected to a 
final cleaning between smooth hardened steel rollers which crush 
the grains of sand which are then washed out. The rubber is then 
well masticated and mixed with sulphur and whatever other ingre- 
dients may be required. The rubber is then forced by hydraulic 
pressure into huge iron moulds which will contain sometimes as 
much as a ton of rubber and which are rectangular or cylindrical 
according to the type of machine which is to cut sheet from them. 
Special care has to be taken to prevent the inclusion of air bubbles 
in this block of prepared rubber. When rubber is compressed in 
this way into cylindrical moulds for manufacture of cut sheet an 
axle of steel is forced through the centre of the mass while still in 
the iron mould. The moulded mass has then been to be annealed 
by gentle heating and maintaining it at a moderate temperature for 
some little while. The next process is to harden the block by 
freezing for a week in a refrigerating room, where it remains after 
removal of the mould until wanted for use. The cutting edge of 
the knife, and the surface of the rubber, are plentifully lubricated 
with water during cutting, this also- fulfils the further purpose of 
thawing the immediate surface of the rubber and bringing the 
rubber to a suitable condition of hardness for the operation. The 
sheet, when cut must be carefully handled, being still soft and self 
adherent, unvulcanised, though perhaps containing mixed sulphur. 
DIPPED GOODS. 
33. There is still another mode of manufacture of hollow rubber 
goods which may be called the dipping process, it is simple in 
principle and very similar to the way in which the old-fashioned 
tallow dip candles were made. A thick rubber solution is prepared, 
usually of pure rubber and solvent, though pigments may be mixed 
with it. A mould representing the internal shape of the required 
article is dipped into this liquid and withdrawn. The solvent 
evaporates leaving a film of rubber on the moulds, the operation is 
repeated until the required thickness of rubber is accumulated. 
Any manipulation or cleaning of the edges is now carried out and 
the rubber still on the mould is vulcanised. Here the “cold cure” 
has to be adopted, since the rubber contains no sulphur already 
mixed, and the customary solution of 3 per cent, of sulphur chloride 
in carbon bisulphide is employed as previously described under the 
head of vulcanisation. Certain classes of surgical rubber goods 
are made in this fashion and india-rubber teats for feeding bottles 
are turned out by the thousand. A final dressing of rubber enamel 
