ions_

Just here, in order to assure a better understanding of the subject, it
may be well to clear up sundry misconceptions regarding the words
percolation, filtration, decoction, infusion, etc., by the simple
expedient of definition.

A decoction is a liquid produced by boiling a substance until its
soluble properties are extracted. Thus the coffee drink was first a
decoction; and a decoction is what one gets today when coffee is boiled
in the good old-fashioned way--as "mother used to make it."

Infusion is the process of steeping--extraction without boiling. It is
extraction accomplished at any temperature below boiling, and is a
general classification of procedure capable of sub-division. As
generally and correctly applied, it is the operation wherein hot water
is merely poured upon ground coffee loose in a pot, or in a container
resting on the bottom of the pot. In the strictest sense of the term, an
infusion is also produced by percolation and filtration, when the water
is not boiled in contact with the coffee.

Percolation means dripping through fine apertures in china or metal as
in De Belloy's French drip pot.

Filtration means dripping through a porous substance, usually cloth or
paper.

Percolation and filtration are practically synonymous, although a shade
of distinction in their meaning has arisen so that often the latter is
considered as a step logically succeeding the former. Accomplishing
extraction of a material by permitting a liquid to pass slowly through
it is in fact percolation, whereas filtration of the resultant extract
is effected by interposing in its path some medium which will remove
solid or semi-solid material from it. Coffee-making practise has in
itself so applied these terms that each is considered a complete
process. Percolation is thus applied when the infusion is removed from
the grounds immediately by dripping through fine perforations in the
china or metal of which the device is constructed.

True percolation is not produced in the pumping "percolators" in which
the heated water is elevated and sprayed over the ground coffee held in
a metal basket in the upper part of the pot, the liquor being
recirculated until a satisfactory degree of extraction has been reached.
Rather, the process is midway between decoction and infusion, for the
weak liquor is boiled during the operation in order to furnish
sufficient steam to cause the pumping action.

Filtration is accomplished whe