C. Ainsworth Mitchell

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).

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.

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.