now, it is the universal practice of operators to judge
of the proportion of iodine and bromine in coating the plate, by two
standards of color the one fixed upon for the iodine, the other for the
additional coating of bromine. Now I maintain that these alone form a
very fallacious standard; first, because the color appears to the eye
either lighter or darker, according as there is more or less light by
which we inspect the coating; and secondly, because if it occur that we
are deceived in obtaining the exact tint for the first coating, we are
worse misled in obtaining the second, for if the iodine coating be too
light, then an undue proportion of bromine is used in order to bring it
to the second standard, and vice versa."

The iodine box should be kept clean and dry. The plate immediately
after the last buffing, should be placed over the iodine, and the
coating will depend upon the character of the tone of the impression
desired. Coating over dry iodine to an orange color, then over the
accelerator, to a light rose, and back over iodine one sixth as long as
first coating, will produce a fine, soft tone, and is the coating
generally used for most accelerators. The plate iodized to a dark
orange yellow, or tinged slightly with incipient rose color, coated
over the accelerator to a deep rose red, then back over iodine
one-tenth as long as at first coating, gives a clear, strong, bold,
deep impression.

I will here state a singular fact, which is not generally known to the
operator. If a plate, coated over the iodine to a rose red, and then
exposed to strong dry quick or weak bromine water, so that a change of
color can be seen, then recoated over the iodine twice as long as at
first coating, it will be found far more sensitive when exposed to the
light than when it has been recoated over the iodine one-fourth of the
time of the first coating.

Probably the best accelerating combination is the American compound
formerly known as "Gurney's American compound," or some of the
combinations of bromide of lime. The first is thought to possess
perhaps more uniformity in its action than any other combination I have
ever used.

The plate once coated should be kept excluded from the light by means
of the plate holder for the camera box.

I will notice one of the principal causes having a tendency to prevent
the perfect uniformity of chemical action, between the iodine and
silver; hydrogen, or the moisture in the atmosph