DISTINGUISHING INKS IN HANDRWRITING
Elizabethan Ink--Milton's Bible--Age of Inks--Carbon Inks--Herculaneum
MSS.--Forgery of Ancient Documents.
In order to make clear the principles upon which are based the methods of
distinguishing between different kinds of ink in handwriting it is
necessary to give some account of the nature of ink.
Ordinary writing ink is essentially a mixture of a decoction of galls (or
other substances containing tannin) with a solution of copperas, or as it
is now termed, ferrous sulphate. These substances combine with one another
to form a tannate of iron, which gradually changes on exposure to the air
into another iron tannate, which is insoluble and constitutes the black
pigment of writing.
Characters written with a pure freshly-prepared iron gall ink are very
faint in colour when first applied to the paper, and it is only after the
air has acted upon them that they gradually become dark blue and finally
black.
In the old type of iron-gall ink, that which was universally employed down
to the early part of last century, inks were exposed to the air or were
boiled in order that the insoluble black pigment might form within the
liquid, and thus give some colour to the ink when it was first put upon
paper. The objection to this is that ink thus prepared is liable to clog
the pen and not to penetrate properly into the fibres of the paper.
In the modern type of inks, therefore, which are commonly known as
"blue-black" inks, this method of partial oxidation is not employed, but a
colouring matter is added instead, so that the writing has some colour
immediately, pending the formation of the black pigment within the fibres
of the paper.
The nature of this provisional colouring matter varies in different inks,
and no two manufacturers appear to use the same substance for this
purpose. In some inks indigo is employed, in others logwood, while the
introduction of aniline dyestuffs placed an abundant choice of colouring
matters at the disposal of the manufacturer.
In the case of old inks it would only have been possible to distinguish
between writings done with different kinds where some mistake had been
made in the preparation of the ink, and a large excess of iron or of galls
had been used.
The possibility of such mistakes occurring, however, will be readily
understood when it is remembered that ink-making was formerly as much a
part of the duties of the housewife as the baking of bread or the making
of cordials.
As writing was a polite accomplishment restricted to the educated people
of leisure the ink-manufacturer could not have existed, for there would
have been no customers, and recipes for the making of ink were therefore
handed down for generations.
A particularly interesting example of an early domestic recipe for making
ink is shown in the accompanying figure which Mr. G. Weddell has kindly
allowed to be reproduced. This was taken from a collection of old family
recipes dating back to the early part of the sixteenth century, and
including among its odd assortment of items directions for making
everything needed for the household, from apple pasties to cures for the
king's evil. This particular recipe, which was one of several for making
ink, was probably written towards the close of the sixteenth century. It
gives directions for soaking the galls in rain water (or claret, or red
vinegar) and boiling the liquid, after standing for a few days, with
copperas and gum. The whole collection of these recipes, which suggest
many a picture of the life in an English household in the sixteenth
century, has been published in facsimile (_Arcana Fairfaxiana
Manuscripta_, 1890).
[Illustration: Elizabethan domestic recipe for ink]
Ink made by the rule of thumb methods of the housewife must have often
been very poor stuff, and it is to this cause that we must attribute the
want of permanency of the ink in some of the relatively modern writing as
compared with that upon manuscripts centuries earlier.
No more interesting illustration of the effect of the composition of old
inks upon the permanency of writing can be found than in the various names
written in Milton's family Bible, to be seen in the British Museum. It
will be noticed that all the entries of the births of himself and the
members of his family are in the handwriting of Milton, and that with one
exception all the inks are of a good dark tone. The exception is seen in
the entry relating to the birth of his daughter Deborah "on the 2nd of
May, being Sunday, somewhat before three of the clock in the morning,
1652." Here the ink has faded to a faint brown tint.
Considerable variations are possible in the proportions of galls and iron
that may be used without interfering with the blackness of the pigment,
but a deficiency of tannin outside those limits will cause the writing to
turn brown. A lack of tannin to combine with the excess of iron present is
probably the explanation of this faded entry in Milton's Bible.
It is very probable, too, that tests applied to the freshly-written
entries would have shown that the ink in this entry was of different
composition from that of the inks in the other entries.
Lovibond's tintometer, an instrument which enables slight differences of
colour to be distinguished more accurately than is possible with the naked
eye, has been used in matching the colour obtained in chemical reactions
with those given by the colour scales prepared from known or suspected
inks.
For recording colour, strips of glass graduated so as to form a series of
colour scales are employed in this instrument, and in this way a note can
be taken of any given tint.
[Illustration: The Tintometer]
The first occasion upon which this instrument was employed in criminal
work was in the Brinkley poisoning case, in which the colours of the
different inks upon the will and other documents were examined by its
means.
The problem of determining the age of an ink in writing is much more
difficult than that of deciding whether two writings are in the same or in
a different kind of ink.
It is, as a rule, possible to distinguish, with the aid of the microscope
and tintometer, between freshly-written and old writing up to about the
sixth day, after which the black pigment has attained sufficient intensity
to prevent further differentiation until after the lapse of two or three
years or more, when the provisional pigment will have faded or have become
fixed by the iron tannate.
In most cases the provisional pigments used offer greater resistance to
the action of chemicals, but are infinitely less stable than the iron
tannate when exposed to the action of light and air, and eloquent
testimony to this difference is given by the comparison of certain
manuscripts of the seventh and eighth centuries with typewritten matter in
aniline ink, which has been put aside for a few years.
Thus it happens that when characters written in blue-black ink are kept,
the blue pigment will gradually fade out, leaving the black pigment; and
when this stage is reached the ink in old writing is readily distinguished
from ink that has been freshly put upon paper.
Prior to this, however, the blue provisional colouring matter appears to
become enveloped in the particles of iron tannate so that it no longer
reacts rapidly with chemical reagents.
Thus, if writing done within the last year or two be treated with acetic
acid there is an immediate diffusion of the blue pigment, whereas in the
older writing, diffusion, if it occurs at all, is very slow and limited in
extent.
A still more useful reagent for this purpose is a saturated solution of
oxalic acid, which causes the pigment of relatively fresh writing to give
an immediate smudge, but has very little, if any, effect on writing six or
eight years old. The differences in the behaviour of old and relatively
recent writing are seen in the tests here illustrated, in which the old
writing of 1898 was hardly affected by the reagents, whereas the writing
done in 1908 gave the results shown.
Both writings were in the same kind of ink and the tests were applied
simultaneously.
Speaking generally, a writing done with blue-black ink ceases to show such
diffusion after five to six years. When slight diffusion occurs in an
older ink it is seen under the microscope to differ in character and only
to affect the surface of the letters, whereas the diffusion in an ink
written within the last two or three years affects the whole of the
pigment in the letters.
The first occasion on which chemical evidence as to the age of blue-black
ink has been given in the law courts was in the recent forgery case, in
which Colonel Pilcher was accused of forging his cousin's will. This will
was alleged to have been written in 1898; and assuming this to have been
the case, the ink should only have reacted very slowly with the different
reagents; there should have been little or no diffusion with oxalic acid:
and if any slight diffusion occurred it should only have been upon the
surface of the letters.
The ink upon the will, however, gave an immediate reaction with the
different reagents, the blue pigment diffused at once with oxalic acid,
and the diffusion extended throughout the whole of the letters. There was
thus no doubt but that the ink upon the will had been written within the
last year or two--certainly within the last six years.
Cheques written by the deceased lady during the last thirteen years were
also subjected simultaneously to the same tests, and while those written
quite recently gave an immediate diffusion, the ink upon those written in
1903 showed only the slightest diffusion in the heaviest writing, and no
diffusion at all was obtained upon the cheques written in 1901.
The general adoption of blue-black ink for the old iron-gall ink has made
it a simple matter to distinguish between old and new writing, for it is
easy to differentiate the two kinds of ink by tests which show the
presence of the blue pigment.
The test has been found useful of late in checking the statements of
certain claimants of old-age pensions, who, as a proof of their age, have
pointed to the entries of date of their birth in old family Bibles.
In more than one instance the results of a scientific examination of the
inks have failed to support the claim, for they have proved conclusively
that the ink was of recent origin.
It is a simple matter to distinguish between the ancient types of ink that
were in use during the early centuries of the Christian era until they
were gradually replaced by iron-gall inks and modern writing inks. For the
basis of all these ancient inks is lampblack, or some other form of
carbon, which is very resistant to the action of reagents. It is for this
reason that printing ink, the pigment of which is carbon, is so much more
stable than any ordinary writing ink can be. In fact, in order to increase
the permanence of writing inks it has frequently been recommended to add
a small amount of some carbon ink.
The most easily obtained preparation of the kind is the commercial Indian
or Chinese ink, which consists essentially of a mixture of glue with
lampblack in the finest possible state of division.
In order to distinguish between a carbon ink of this nature and an
ordinary writing ink all that is necessary is to apply a dilute bleaching
agent. The blue-black pigment of the writing ink will then gradually
disappear, whereas the fine particles of carbon in the other ink will show
little, if any alteration, and may still be discerned under the microscope
as minute black granules resting upon the fibres of the paper.
It was by a method similar to this that Sir Humphrey Davy proved that the
writing upon papyri found in the ruins of Herculaneum, which was destroyed
in A.D. 79, had been done with a carbon ink, of the same nature as that
used by the ancient Egyptians and by the Chinese and Japanese at the
present day. On none of the Herculaneum MSS. could any trace of iron ink
be detected.
The same tests may be applied to determine whether the writing upon a
document has been lithographed or has been written with ordinary ink.
An amusing instance of the kind came within the present writer's
experience. A sheet of paper upon which was some writing that was believed
to have been written by Nelson had been handed down in a family for
several generations as an heirloom, and had always been looked upon as a
genuine document. The ink had the faded yellow tone of old iron ink, and
there was nothing to show that the writing was not what it professed to
be.
Its present owner, however, happened to notice in a museum what appeared
to be a duplicate of the manuscript in his possession, and when a chemical
test was applied to the ink upon the latter the pigment was quite
unaffected. Hence there could be no doubt as to its being a copy of the
original reproduced by lithography.
Cases in which it is necessary to distinguish between iron-gall writing
inks and printing or other carbon inks occur from time to time in criminal
investigations. As a recent example a case that was tried a few months ago
may be mentioned. The chief clerk of a firm of merchants had for a
considerable time been defrauding his employers, and when suspicion at
length fell upon him, endeavoured to conceal his doings by falsifying the
entries of previous years in the ledger.
In order to do this it was necessary to abstract certain pages in a
particular part of the ledger and to substitute the necessary alterations.
Then, finding that the ink of the writing would appear too new, and thus
invite inquiry, he added a small amount of Indian ink to an ordinary
writing ink, and thus obtained a mixture, which gave an immediate effect
of age to the writing. To the naked eye there was nothing to show that
these pages had not been written on the dates mentioned on them, three or
four years previously, but on applying a weak bleaching agent the fraud
was at once made obvious. The iron-gall part of the pigment faded away,
but the particles of carbon that had formed the basis of the Indian ink
were left, and their nature could easily be recognised under the
microscope. The entries on the other pages in the ledger, which had been
written in ordinary writing were completely bleached in the test.
A very curious illustration of the difficulties that beset the forger of
ancient documents was afforded by the trial of Humphreys in 1839 in
Edinburgh.
The prisoner was the claimant to the earldom of Stirling, and in support
of his claim had produced a number of documents supposed to date back to
the seventeenth and early eighteenth centuries. One of these purported to
be a portion of a charter granted by King Charles I to the first Earl of
Stirling in 1639, permitting the succession to the earldom to descend
through the daughters of the house.
As witness to this there was appended the signature of Archbishop
Spottiswood described as "our Chancellor," whereas as a matter of history
the seal had been handed to the Marquis of Hamilton a year prior to the
date of the pretended charter. There were also various other anachronisms
in the document, such as margins in red ink, which were not used before
1780.
Scientific evidence was also given that the ink upon the pretended charter
was not old ink, but ink that had been treated in such a manner as to
appear old.
Similar inconsistencies were shown in the other pieces of documentary
evidence, and scientific proof was given that the date upon an engraved
map, upon the back of which were memoranda supporting the claimant's case,
had been added at a later period.
The jury unanimously found the prisoner guilty of forgery.