325] says:

It is a growing belief that in roasts of short duration the largest
percentage of the aromatic properties is retained. A slow roast has
the effect of baking and does not give full development; also, slow
roasts seldom produce bright roasts, and they usually make the
coffee hard instead of brittle, even when the color standard has
been attained.

[Illustration: FRENCH GAS COFFEE-ROASTING PLANT EQUIPPED WITH MODERNE
MACHINES]

While coffees of widely varying degrees of moisture require somewhat
different treatment, the consensus of opinion is that the best results
are obtained from a slow fire at the beginning, until some of the
moisture has been driven off, when the stronger application of heat may
be given for development. An intense heat in the beginning often results
in "tipping", or charring, the little germ at the end, the most
sensitive part of the bean.

Scorched beans have been caught at some point in the cylinder, often in
a bent flange. Burning on one face, sometimes called "kissing the
cheeks", is caused by the too rapid revolution of the cylinder, so that
some of the coffee "carries over". In the best practise, crowding of
cylinders is avoided; many roasters making it a rule not to exceed
ninety percent of the rated capacity of the cylinder.

Those operating gas roasters may effect a fuel economy by running a low
grade coffee in the cylinder after the last roast has been drawn and the
gas extinguished; five minutes' revolution absorbs the heat and drives
off a proportion of moisture. The coffee, which may then be left in the
cylinder, requires less time and fuel in the morning, and the roast is
finished while the cylinder is warming up. Double roasting brightens a
roast, but is a detriment to the cup quality. A dull roasting coffee may
be improved by revolving the green coffee in a cylinder without heat for
twenty minutes, which has the effect of milling.

The use of a small amount of water upon roasts gives better control by
checking the roast at the proper point--the crucial time of its greatest
heat; also, it swells and brightens the coffee, and tends to close the
outer pores. While the addition of water is open to abuse, few roasters
have soaked their coffees enough to offset the natural shrinkage as much
as three or four percent. Such practise would result greatly to the
detriment of the cup quality.

There is no universal standard for the degree to which