128 EXPLOITATION OF PLANTS 
have a differential motion in regard to the jacket. In 
due course the leaf is discharged from the machine, 
the process occupying from fifteen to sixty minutes, 
according to type of machine employed, character of 
leaf, and size of charge. Short periods of rolling con- 
stitute “light” rolling; longer periods, ‘‘ heavy’ 
rolling. After a sifting, and a re-rolling of older leaves, 
the next stage is the— 
3. Fermentation —When small quantities of leaf are 
dealt with, the leaf is placed on shelves, or in trays 
arranged in racks ; but in large factories special ferment- 
ing floors, made of cement, tiles or even plate-glass are 
employed, the twisted ruptured leaf being spread out 
in thin layers one or two inches deep to give full access 
to the air, which should be freely admitted. The 
optimum temperature is about 80° F., and the atmo- 
sphere is kept moist by means of suspended wet cloths. 
Similar cloths are also arranged over but just clear of 
the leaf. The floors, cloths and everything connected 
with the fermenting house (which is kept relatively cool 
and darkened) should be maintained scrupulously clean 
by frequent steaming and scouring, to prevent the 
growth of putrefactive bacteria, which are very detri- 
mental to the production of good-class tea. During the 
fermentation, which lasts a few hours (but may be much 
shorter), the leaf changes colour, and gives evidence of 
becoming tea as distinct from leaf. When the fermen- 
tation is complete, the final major operation takes place, 
the so-called— 
4. Firing.—This process, originally effected over open 
charcoal fires, is now carried out entirely by automatic 
machinery. The tea is fired or dried by means of hot 
