The inks in common use over the United States at the present time,
and for some years past, are not as numerous as one might be led
to conclude. They are probably fifteen or at most twenty in all,
including the most popular blue, red, magenta, and green inks. But
among these there is a notable difference in character. Some are
thick, heavy, and glossy, in character, and flow sluggishly from the
pen. Few of these become much darker by standing. In this class will
be found the copying inks and those in which a large quantity of gums
or similar thickening agents are used.
Other inks are pale, limpid, and flow easily from the pen, and this
class usually shows a notable darkening by exposure to sunlight and
air. It will be unnecessary here to refer more particularly to the
intermediate varieties or to discuss their various composition.
It should be, remembered here that in the last twenty years, or since
the introduction into general commerce of aniline colors, which
Hofmann discovered in 1856, these latter have been employed more and
more in writing fluids; not only in mixtures of which they are the
principal ingredients, but to a greater or less degree in all inks.
Their presence, even in small quantity, in the gallo-tannate of iron
and logwood inks can be generally detected by an iridescent and
To assist in determining the ages of writings by one and the same ink,
it is to be observed that the older the writing the less soluble it is
in dilute ammonia. If the writing be lightly touched with a brush
dipped in ten-per-cent ammonia, the later writing will always give up
more or less soluble matter to the ammonia before the earlier. In case
of inks of different kinds this test is not serviceable, for
characters written in logwood ink, for instance, will always give up
their soluble material sooner than nutgall inks, even if the last
named be later applied. To estimate the age of writing from the amount
of bleaching in a given time by hydrochloric or oxalic acid is very
precarious, because the thickness of the ink film in a written
character is not always the same, and the acid bleaches the thinner
layer sooner than the thicker.
The determination of the age of a written paper is a problem difficult
of solution. According to F. Carre the age can be approximately
determined if the characters written in iron ink are pressed in a
copying press and a commercial hydrochloric acid diluted with eleven
parts of water is substituted for water; or, if the written characters
are treated for some time with this diluted acid.
The explanation is that the ink changes in time, its organic substance
disappears little by little, and leaves behind an iron compound, which
in part is not attacked even by acids.
An unsized paper is impregnated with the described diluted acid,
copied with the press, and a copy from writing eight or ten years old
can be obtained as easily as one by means of water from a writing one
A writing thirty years old gives, by this method, a copy hardly
legible, and one over sixty years old, a copy hardly visible. In order
to protect the paper against the action of the acid, it should be
drawn through ammoniacal water.
To determine the exact age of writings by the ink is not easy. The
approximate age may be determined with some degree of certainty. If
ink-writings are but a few days old, it is easy to distinguish them
from other writing years old. But to tell by the ink which of two
writings is the older, when one is but two months and the other two
years, is, as a rule, impossible.
Where during the progress of a trial a document purporting to be years
old is introduced in evidence, and it can be shown that it is but a
few days old, having been prepared for the occasion, ordinarily the
age of the writing will be comparatively easy of demonstration by the
expert. Oxidization will not have set in to any extent, if the ink is
very fresh, and this, with a careful watching of the color for any
darkening, will determine whether or not the ink is fresh. This ink
study should be a question of the utmost interest to bankers and bank
A ten-per-cent solution of ammonia applied to two inks in question
will show which is the fresher. The older ink will resist the action
of the ammonia longer and give up less soluble matter than the newer
writing. Nutgall, and logwood inks, of course, should not be tested
comparatively by this method, as the logwood ink will respond to the
ammonia sooner than the nutgall ink.
F. Carre also gives another method for determining, approximately, the
age of ink-writings. If the writing is in iron ink, and is moistened
with a solution of one part of hydrochloric acid to eleven parts of
water and put in letter-copying press and copy transferred to copy
paper it should give a strong copy, if but ten years old; a hardly
legible copy, if thirty years old; and if sixty years old, a few marks
will be copied, but they will not be legible.
If the same solution be used in place of water, as in the ordinary
letter-copying process and the copying paper be saturated with it, the
result will be the same.
To determine the age of writing by applying bleaching acids and
watching results and counting the seconds is a dangerous method. Thick
inks will respond to the acids slower than thin, and the time
comparisons are misleading.
Safety inks, so-called, designed to resist the action of acids and
alkalies have been repeatedly put upon the market, but no such ink has
ever successfully challenged the world and proved its title of safety.
Many chemicals are recommended as restorations for faded writing, but
these should be avoided as far as possible, as they are liable to
stain, disfigure the paper, and in the end make matters materially
worse. Familiarity with particular handwritings after some practice
will enable the reader to make out otherwise unintelligible words
without any other assistant than a powerful magnifying glass.
If the ink is very faint, the simplest and most harmless restorative
is sulphate of ammonia, but its loathsome smell once encountered is
not easily forgotten. The experiment in consequence is very seldom
repeated for the result is scarcely good enough to risk a repetition
of so horrible a smell.
The writing on old and faded documents may be restored, by chemical
treatment, turning the iron salt still remaining into ferrous sulphate.
A process which will restore the writing temporarily is as follows: A
box four or five inches deep and long and broad enough to hold the
document, with a glass, is needed. A net of fine white silk or cotton
threads is stretched across the box at about one half the depth. Two
saucers containing yellow ammonium hydrosulphide are placed in the
bottom of the box. By means of a clean sponge or brush, moisten the
paper with distilled water; then place it on the net with the writing
side down. The action of the vapor of the ammonium hydrosulphide will
cause the obliterated writing to slowly turn brown, then black. But
within a short time after removal from the box the writing will again
Another method is to wash the document carefully in a solution of
hydrochloric acid, one part, and distilled water, one hundred parts.
Dry the moistened paper somewhat, leaving it just moist enough to hold
a uniform layer of fine yellow prussiate of potash. A plate of glass
with a light pressure should be placed on this. In a few hours dry the
paper thoroughly, and carefully brush off the yellow prussiate of
potash. The writing should come out a Prussian blue. This restored
writing will be permanent unless exposed too much to the light.
The hydrochloric acid must be thoroughly removed; otherwise, it will
destroy the paper. Crystallized soda, two parts, and distilled water,
one hundred parts, in solution, will counteract the hydrochloric acid,
if the document is allowed to float on it for twenty-four hours.