Young operators are apt to impute all want of success in operating to
their chemicals, even though the cause is quite as likely to be
elsewhere. Failure is quite likely to occur from dampness in the
buffs, or in the polish; it is therefore necessary to be constantly on
the guard in this quarter. With a view to this, always scrape your
buffs with a dull knife, or with one blade of your shears, the first
thing in the morning, and after brushing them thoroughly, dry them,
either in the sun, by a stove, or in the buff-dryer. It is equally
important that the polish and the brush should be kept dry.

Want of success may arise from vapors of iodine or bromine in the
camera box, mercury bath, or even in the buffs. It is incredible how
small a quantity of these vapors will affect the effect of light when
coming in contact with the plate, after or during the exposure in the
camera. It is therefore necessary to be cautious not to mix chemicals,
nor open your boxes or bottles in your room, but take them out to do
it. Never hurry the operation through from lack of confidence in the
result. The fact of anything being out of order, forms no excuse for
slighting the process. If unsuccessful, do not pursue the same course
every trial, but vary with a view to detect the cause of the difficulty.

In case of a long series of failures, institute a regular course of
investigation, after this manner, commencing where the trouble is most
likely to occur:

1. Are the plates well cleaned?

2. Is the iodine dry? If the impressions come out blue, you may rest
assured it is not. Take out the iodine, wipe and dry the box, and dry
the calcium.

3. Is the quick battery of the right strength? If dry, it must change
the plate in from six to fifteen seconds. If any of the chloride of
iodine class, it may vary from five seconds to a minute. Begin by
coating light, and increase on each trial, observing the effect. If
the light side of the picture seems loth to come out, and shows no
contrast with the dark side, it is to be inferred that your battery is
too strong, and must be reduced with water or set out in the open air
for a few minutes, with the lid off. If working an old battery, never
renew very strong, or it will work dark and heavy. A battery, to work
well, should be gradually losing strength, but never gaining. An old
battery, however, may be quickened up and made to work well for some
time, by adding five of six drops of