THE increasing demands for ink, and the lack of interest as to its
composition during the eighteenth century, if viewed in the same lights which
prevail in our own times, permitted the general manufacture of cheap grades of
ink which possessed no very lasting qualities. The chemistry of Inks was not
fully understood, indeed we find Professor Turner of the College of Edinburgh
declaring in 1827:
“Gallic acid was discovered by Scheele in 1786, and exists ready formed in
the bark of many trees, and in gall-nuts. It is always associated with tannin, a
substance to which it is allied in a manner hitherto unexplained. It is
distinguished from tannin by causing no precipitate in a solution of gelatine.
With a salt of iron it forms a dark blue coloured compound, which is the basis
of ink. The finest colour is procured when the peroxide and protoxide of iron
are mixed together. This character distinguishes gallic acid from every other
substance excepting tannin.”
The general lack of information or knowledge respecting ink chemistry or its
time-phenomena was not confined to any particular country, and it does not
appear that any general or specific attention was scientifically directed to it
until 1765, when William Lewis, F. R. S., an English chemist, publicly announced
that he proposed to investigate the subject. His experimentations covered a
period of many years and their results and his theories as to the phenomena of
inks were published in 1797. The most valuable of his conclusions were that an
excess of iron salt in the ink is detrimental to color permanence (such ink
becoming brown on exposure) and also that acetic acid in the menstruum provides
an ink of greater body and blackness than sulphuric acid does (a circumstance
due to the smaller resistance of acetic acid to the formation of iron
gallo-tannate). Many of his other observations were later shown to have been
erroneous. Dr. Lewis was the first to advocate log-wood as a tinctorial agent in
connection with iron and gall compositions.
Ribaucourt, a French ink maker, in 1798 determined that an excess of galls is
quite as injurious to the permanence of ink as an excess of iron.
Pending the completion of the researches of Lewis, the Royal Society of
England, affected by complaints from all quarters relative to the inferiority of
inks as compared with those of earlier times, brought the subject to the
attention of many of its members for discussion and advice. Its secretary,
Charles Blagden, M. D., read a paper before the society, June 28, 1787, which
was published in the “Philosophical Transactions” and widely circulated. It is
so interesting that copious extracts are given:
“In a conversation some time ago with my friend Thomas Astle, Esq., F. R. S.
and A. S., relative to the legibility of ancient MSS. a question arose, whether
the inks in use eight or ten centuries ago, which are often found to have
preserved their colour remarkably well, were made of different materials from
those employed in later times, of which many are already become so pale as
scarcely to be read. With a view to the decision of this question, Mr. Astle
obligingly furnished me with several MSS., on parchment and vellum, from the
ninth to the fifteenth centuries inclusively, some of which were still black,
and others of different shades of colour, from a deep yellowish brown to a very
pale yellow, in some parts so faint as to be scarcely visible. On all of these I
made experiments with the chemical re-agents which appeared to me best adapted
to the purpose, namely, alkalis both simple and phlogisticated, the mineral
acids, and infusions of galls.
“It would be tedious and superfluous to enter into a detail of the particular
experiments, as all of them, one instance only excepted, agreed in the general
result, to shew that the ink employed anciently, as far as the above-mentioned
MSS. extended, was of the same nature as the present; for the letters turned of
a reddish or yellow brown with alkalis, became pale, and were at length
obliterated, with the dilute mineral acids, and the drop of acid liquor which
had extracted a letter, changed to a deep blue or green on the addition of a
drop of phlogisticated alkali; moreover, the letters acquired a deeper tinge
with the infusion of galls, in some cases more, in others less. Hence it is
evident, that one of the ingredients was iron, which there is no reason to doubt
was joined with the vitriolic acid; and the colour of the more perfect MSS.
which in some was deep black, and in others purplish black, together with the
restitution of that colour, in those which had lost it, by the infusion of
galls, sufficiently proved that another of the ingredients was a stringent
matter, which from history appears to be that of galls. No trace of a black
pigment of any sort was discovered, the drop of acid which had completely
extracted a letter, appearing of an uniform pale ferrugineous color, without an
atom of black powder, or other extraneous matter, floating in it.
“As to the durability of the more ancient inks, it seemed, from what occurred
to me in these experiments, to depend very much on a better preparation of the
material upon which the writing was made, namely, the parchment or vellum; the
blackest letters being those which had sunk into it deepest. Some degree of
effervescence was commonly to be perceived when the acids came into contact with
the surface of these old vellums. I was led, however, to suspect, that the more
modern; for in general the tinge of colour, produced by the phlogisticated
alkali in the acid laid upon them, seemed less deep; which, however, might
depend in part upon the length of time they have been kept: and perhaps more gum
was used in them, or possible they were washed over with some kind of varnish,
though not such as gave gloss.
“One of the specimens sent me by Mr. Astle, of the fifteenth century, and the
letters were those of an engrossing hand, angular, without any FINE strokes,
broad and very black. On this none of the above-mentioned re-agents produced any
considerable effect; most of them seemed to make the letters blacker, probably
by cleaning the surface; and the acids, after having been rubbed strongly on the
letters, did not strike any deeper tinge with the phlogisticated alkali. Nothing
had a sensible effect toward obliterating these letters but what took off part
of the surface of the vellum, when small rolls, as of a dirty matter, were to be
perceived. It is therefore unquestionable, that no iron was used in this ink;
and from its resistance to the chemical solvents, as well as a certain clotted
appearance in the letters when examined closely, and in some places a slight
degree of gloss, I have little doubt but they were formed with a composition of
a black, sooty or carbonaceous powder and oil, probably something like our
present printer’s ink, and am not without suspicion that they were actually
printed (a subsequent examination of a larger portion of this supposed MSS. has
shown that it is really a part of a very ancient printed book).
“Whilst I was considering of the experiments to be made, in order to
ascertain the composition of ancient inks, it occurred to me that perhaps one of
the best methods of restoring legibility to decayed writing might be to join
phlogisticated alkali with the remaining calx of iron, because, as the quantity
of precipitate formed by these two substances very much exceeds that of the iron
alone, the bulk of the colouring matter would thereby be greatly augmented. M.
Bergman was of opinion that the blue precipitate contains only between a fifth
and a sixth part of its weight of iron, and though subsequent experiments tend
to show that, in some cases at least, the proportion of iron is much greater,
yet upon the whole it is certainly true, that if the iron left by the stroke of
a pen were joined to the colouring matter of phlogisticated alkali, the quantity
of Prussian blue thence resulting would be much greater than the quantity of
black matter originally contained in the ink deposited by the pen, though
perhaps the body of colour might not be equally augmented. To bring the idea to
the test, I made a few experiments as follows:
“The phlogisticated alkali was rubbed upon the bare writing in different
quantities, but in general with little effect. In a few instances, however, it
gave a bluish tinge to the letters, and increased their intensity, probably
where something of an acid nature had contributed to the diminution of their
colour.
“Reflecting that when phlogisticated alkali forms its blue precipitate with
iron the metal is first usually dissolved in an acid, I was next induced to try
the effect of adding a dilute mineral acid to writing besides the alkali. This
answered fully to my expectations, the letters changing very speedily to a deep
blue colour, of great beauty and intensity.
“It seems of little consequence as to the strength of colour obtained,
whether the writing be first wetted with the acid, and then the phlogisticated
alkali be touched upon it, or whether the process be inverted, beginning with
the alkali; but on another account I think the latter way preferable. For the
principal inconvenience which occurs in the proposed method of restoring MSS.
is, that the colour frequently spreads, and so much blots the parchment as to
detract greatly from the legibility; now this appears to happen in a less degree
when the alkali is put on first, and the dilute acid is added upon it.
“The method I have hitherto found to answer best has been to spread the
alkali thin with a feather or a bit of stick cut to a blunt point, though the
alkali has occasioned no sensible change of colour, yet the moment that the acid
comes upon it, every trace of a letter turns at once to a fine blue, which soon
acquires its full intensity, and is beyond comparison stronger than the colour
of the original trace had been. If now the corner of a bit of blotting paper be
carefully and dexterously applied near the letters, in order to suck up the
superfluous liquor, the staining of the parchment may be in a great measure
avoided: for it is this superfluous liquor which absorbing part of the colouring
matter from the letters becomes a dye to whatever it touches. Care must be
taken not to bring the blotting paper in contact with the letters, because the
colouring matter is soft whilst wet, and may easily be rubbed off. The acid I
have chiefly employed has been the marine; but both the vitriolic and nitrous
succeed very well. They should undoubtedly be so far diluted as not to be in
danger of corroding the parchment, after which the degree of strength does not
seem to be a matter of much nicety.
“The method now commonly practiced to restore old writings, is by wetting
them with an infusion of galls in white wine.”
(See a complicated process for the preparation of such a liquor in Caneparius
De Atramentis, A. D. 1660, p. 277)
“This certainly has a great effect; but is subject, in some degree, to the
same inconvenience as the phlogisticated alkali, of staining the substance on
which the writing was made. Perhaps if, instead of galls themselves, the
peculiar acid of or other matter which strikes the black with iron were
separated from the simple astringent matter, for which purpose two different
processes are given by Piesenbring and by Scheele, this inconvenience might be
avoided. It is not improbable, likewise, that a phlogisticated alkali might be
prepared better suited to this object than the common; as by rendering it as
free as possible from iron, diluting it to a certain degree, or substituting the
volatile alkali for the fixed. Experiment would most likely point out many other
means of improving the process described above; but in its present state I hope
it may be of some use, as it not only brings out a prodigious body of colour
upon letters which were before so pale as to be almost invisible, but has the
further advantages over the infusions of galls, that it produces its effect
immediately, and can be confined to these letters only for which such assistance
is wanted.”
The Society of Arts in 1830, received a communication from Dr. Bostock, in
the course of which he stated that the “tannin, mucilage and extractive matter
are without doubt the principal causes of the difficulty which is encountered in
the formation of a perfect and durable ink and for a good ink the essential
ingredients are gallic acid and a sesqui salt of iron.” Owing to his working
with galls he was unable to make decisive experiments, but he concludes, and
that rightly, that in proportion as ink consists merely of gallate of iron, it
is less liable to decomposition and any kind of metamorphosis.
In 1831 the Academy of Sciences in France took up the matter and designated a
committee composed of chemists with instructions to study the subject of a
permanent ink. After long research it reported that it was unable to recommend
any better ink than the tanno-gallate of iron one then in use, but “it should be
properly compounded.”
Peddington investigated, 1841-48, the ancient MSS. collected by the Asiatic
Society of Bengal, Calcutta, and published the results in “Examination of Some
Decayed Oriental Works in the Library of the Asiatic Society,” which are of much
interest as relating to “mineral” inks, the “gall” inks being unknown in Asia
after the twelfth century.
Up to thirty-five years ago, the manufacture of “gall” inks necessitated a
complicated series of processes and long periods of time to enable the ink to
settle properly, etc. It was Professor Penny of the Anderson University who
suggested the way to avoid one of the processes pertaining to ink-making by
utilizing the known fact, that tannin is more soluble in cold than in warm or
hot water. It was adopted all over the world and revolutionized the manufacture
of ink, by doing away with boiling processes and hot macerations of ingredients.
With hardly in exception the best tanno-gallate of iron (“gall”) inks are now
“cold” made.
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LACK OF INTEREST AS TO THE COMPOSITION OF INK DURING PART OF THE EIGHTEENTH
CENTURY—THE CONDITIONS WHICH THEN PREVAILED NEARLY THE SAME AS THE PRESENT
TIME—CHEMISTRY OF INK NOT UNDERSTOOD—THIS LACK OF INFORMATION NOT CONFINED TO
ANY PARTICULAR COUNTRY—LEWIS, IN 1765, BEGINS A SCIENTIFIC INVESTIGATION ON THE
SUBJECT OF INKS - THE RESULTS AND HIS CONCLUSIONS PUBLISHED IN 1797--THE ROYAL
SOCIETY OF ENGLAND IN 1787 RECEIVES COMPLAINTS ABOUT THE INFERIORITY OF INKS -
ITS SECRETARY READS A PAPER THE SAME YEAR—THE PAPER CITED IN FULL—DR. BOSTOCK IN
1830 COMMUNICATES TO THE SOCIETY OF ARTS WHAT HE ESTIMATES TO BE THE CAUSES OF
IMPERFECTIONS IN INK—ACTION OF THE FRENCH ACADEMY OF SCIENCES—COMPLICATIONS
SURROUNDING THE MANUFACTURE OF INK ONLY THIRTY-FIVE YEARS AGO.