86 BULLETIN 13870, U. S. DEPARTMENT OF AGRICULTURE 
the filter cloth. By mtimately mixing with the juice a little suit- 
able inert material, commonly termed a “filter aid,” the juice can be 
rapidly and efficiently filtered without premature clogging of the 
cloth. Infusorial earth, also known as kieselguhr or diatomaceous 
earth, is an effective filter aid; paper pulp and wood flour have also 
been used as filter aids. 
The addition of from 12 to 18 pounds of infusorial earth of a 
good grade to the juice from a ton of cane, followed by heating to 
boiling, makes it possible to filter the juice effectively through a 
plate and frame filter press. The resulting filtrate is clear and ready 
for evaporation to sirup, and no further skimming or other treatment 
ordinarily is required. The color of the resulting sirup depends upon 
the quality of cane from which the juice has been extracted and upon 
the care taken during evaporation to prevent local overheating and 
caramelization. ‘The characteristic flavor of the sirup will be that 
of the cane juice, as the material used for clarification does not chemi- 
cally affect the juice but acts as an inert filter aid, making possible 
the formation of a porous filter cake, which retains the suspended 
particles but permits the juice to flow through freely. 
By this method of clarification only the material originally sus- 
pended in the raw juice, together with that coagulated or sepa- 
rated by heating to boiling, is removed; that is, the material which 
the simple process of boilmg and skimming seeks to remove but ac- 
complishes less effectively. The resulting sirup is not always abso- 
lutely clear, even though the filtrate from the filter press may be 
clear and brilliant, because during the concentration of juice to sirup 
substances which were soluble in the juice gradually become insoluble 
in the more concentrated sirup. The quantity of this material which 
separates from the sirup may vary from a mere trace, provided the 
juice is from cane of satisfactory quality, to a larger proportion, in 
case the cane used is of inferior quality. It is not ordmarily con- 
sidered very objectionable, however. As in the case of the other 
methods of clarification, whenever sediment appears in the sirup after 
every precaution has been taken to thorotahly clarity the juice, the 
best plan is to let the finished sirup remain in settling tanks for 
several days, until as large a proportion as possible of the suspended 
material has setiled to the bottom. 
In some cases the color of sirup made by this process has been 
considered better than that of the average cane sirup made by boiling 
and skimming, owing probably to the fact that no particles of bagasse 
or other trash remain in the filtered juice to adhere to the coils or 
sides of the evaporators, thereby darkening the color by scorching. 
Moreover, the removal of the suspended particles makes possible a 
more rapid evaporation of the juice to strup and permits the man in 
charge to give his entire attention to evaporation, except for such 
skimming as may be required when the sirup reaches higher density. 
It is an advantage also that juice clarified in this way is in suitable 
condition to be evaporated at once under diminished pressure in 
vacuum evaporators. 
This mechanical method of clarification is not practicable for sirup 
makers who operate on a comparatively small scale, using the boiling 
and skimming method and producing usually not more than 200 
gallons of sirup daily, for the reason that it requires a filter press and 
steam supply. In the larger sirup factories, where steam is used to 
