d is governed by the time of contact.

Coffee-tannin, which is not the commercial tannic acid, is
eliminated to practically nothing in the quick brewing methods.

The chemical analysis of brewed coffee shows the following:

Coffee Tannin Comparative
per Cup Proportions

Percolator method,[379] fine gran. 2.90 grains --------
5 minutes' steeping

Boiling Method, medium " 2.35 " ------

Steeping Method, " " 2.31 " -----

Filtration (or Drip) Method } 0.29 " -
Pulverized }

Brewing is the final manufacturing process of coffee. All previous
perfection is dependent upon it. Like food products which lose
nutritive value by bad cooking, coffee loses its best values by
wrong brewing. Brewed by the very simple correct methods, it is an
unfailingly clear, fragrant, taste-charming beverage, universally
loved and scientifically approved.

The committee made a further report in 1914, and some of the findings
were subsequently published in an association booklet called _The Coffee
Book_, used in connection with the second National Coffee Week campaign
in 1915. In it were these:

GRINDING DEFINITIONS

_Powdered_ _Pulverized_
Like--flour. Like--not coarser than
fine corn meal.

_Very Fine and Fine_ _Medium_
Like--from corn meal to Like--coarse granulated
fine granulated sugar. sugar.

Also, the committee emphasized its previous findings, particularly this
one: "Filter bags should be kept in cold water when not in use. Drying
causes decomposition. Keeps sweet if kept wet. Use muslin for filter bag
and pulverized granulation."

The association brought out this same year, on recommendation of the
committee, its Home coffee mill, an "ideal and standard coffee mill for
home use." It was a wall mill equipped with a glass-front metal hopper
and employing a ratchet spring-lock nut and double-action grinders. The
mill was later improved with an all-glass hopper and a tumbler bracket.
More than 20,000 of these mills have been sold.

At the suggestion of the author, the efficiency of nine different
coffee-making devices (including boiling and drip pots, pumping
percolators, cloth and paper filters) w