The investigations of the writer in this direction, while in some respects traveling the same road followed by others, diverged from them and has been more in the nature of a comparative a.n.a.lytical and microscopic examination of ancient with ancient and modern with modern doc.u.ments in connection with numerous chemical experiments, the manufacture of hundreds of inks and the study of their time and other phenomena.

To accomplish this, ancient doc.u.ments not written with "Indian" ink, but with those obviously containing combinations of iron and galls or other tannins, were selected and grouped into color families.

They began with the fourteenth century, continuing well into the nineteenth, to the number of nearly four hundred, each of them of a different date and different year. Some of them were so pale and indistinct as to be illegible, others less so and by gradual steps they approached to a definite black; many of them as rich and deep in color as if they had been written not centuries ago but within a few years. Signatures on the same doc.u.ment represented different degrees of color, so that the question of the material on which the writing appeared affecting the appearance of the ink, was not a factor; but the difference in the inks used to make the signatures was the determining factor.

At this point it may be noted that the investigations conducted by Mr. Swan before referred to and those by the writer and the resultant observations of each were substantially alike. Many of the writer's, however, preceded those of Mr. Swan's, for during the years 1885 and 1886, having had the custody of part of the Archives of the City of New York there were many opportunities to study this subject which were taken advantage of, before and after which time frequent examinations were made of writings much more ancient than those pertaining to New York.

a.s.suming a second premise was to a.s.sert that the inks employed in the writing of these doc.u.ments were "straight" or possessed some "added" pigment or color. Again, the vehicles to hold the particles or possibly preserving substances, might be factors.

All literature possible referring to ink formulas was examined to ascertain the names of materials recommended or formerly "added" to gall inks, because if the pristineness of the blacker inks was due to the added pigment it was a safe proposition that it was still existent in the ink, and that if it could be discovered part at least of the problem would be, simplified.

The "added" color compounds, excluding those of the aniline family which pertain to the more modern ink compositions, are of two cla.s.ses: those possessing tannin and color-yielding materials and those containing only a color-yielding material. Many of the first cla.s.s have been used in the manufacture of ink both with infusions of nut-galls or alone, while but very few of the second cla.s.s have been used for either purpose.

The decomposing action of light, oxygen and moisture on many of each cla.s.s placed them beyond the purview of consideration, while the dates of the discovery and the fact of the small percentage of tannin contained in others permitted them also to be discarded. For instance: vanadium, which is fairly permanent, was discovered only in 1830; chanchi, the ink plant of New Granada discovered in the sixteenth century, possessing excellent lasting qualities, does not a.s.similate perfectly with other const.i.tuents used in the manufacture of ink, but is best when used alone; Berlin blue (prussian blue) is well spoken of, but was only discovered by accident in 1710 by Diesbach, a preparer of colors at Berlin; logwood, more used for this purpose than any other material, was first imported into Europe in the sixteenth century and causes a deterioration of the durable qualities of the tanno-gallate of iron; Brazil-wood and archil, and their allies, are exceedingly fugitive; bablah, the fruit of the acacia arabica, myrabolams, of Chinese growth, catechu, and sumac which though used in the time of Pliny, each contains a percentage of gallic acid too small to meet the requirements.

Divi-divi, a South American product, came into use only at the end of the sixteenth century and has not stood the test of time.

This sifting process completely eliminated all but lampblack, madder and indigo in some form as a permanent "added" color pigment. Lampblack, which is we know forms the basis of "Indian" ink, is not soluble and requires a very heavy gummy vehicle to prevent its immediate precipitation, and while it could have been used in combination with tanno-gallate of iron as an ink, the fact that it was possible to chemically remove the ancient inks which remained black, was a sufficient demonstration that this carbon substance, which is not affected by chemicals, either as contained in the fluid ink or as dusted on after writing, could have formed no part of the ancient tanno-gallate of iron inks.

Madder is mentioned as of very ancient times and was cultivated in Europe as early as the tenth century; its addition to an iron and gall ink is said to be an invention of the year 1855; it is certain, however, that it was used for a like purpose as early as 1826, and a fair presumption that it was frequently employed in some form during the preceding four centuries. It has under certain conditions very lasting properties as the madder-dyed cloths found wrapped around Egyptian mummies demonstrates, but does not a.s.sist the tanno-gallate of iron to retain its black color; on the contrary it seems to lessen this quality.

That indigo for added color was employed by ink manufacturers in the eighteenth century is shown by the formulas appearing in the literature of that time.

It was used alone as an ink long before, as well as contemporaneously with, those of the tanno-gallate of iron family. Its lasting properties are most remarkable if it be true that, used as a dye, there is still in existence specimens of it on cloth five thousand or more years old. The history of its use ALONE as an ink is difficult to ascertain back of a certain period; the writer has several specimens of it, one written in 1692 whose color is a green blue; another written about a century ago is believed to be as bright blue as the day it was placed on the paper; from 1810 to 1850 it was in common use particularly in hot climates where it was "home-made." Consequently if the old "gall" inks contained a lasting added color, indigo must have been the one, Dr. Stark whose investigations along this line for twenty-three years have already been cited has said that he preferred for his own use an ink composed of galls, sulphate of indigo and copperas (sulphate of iron); this means a tanno-gallate of iron ink with indigo for "added" color. Like formulas calling for different proportions of const.i.tuents both before and after his time in England and the continents of Europe and America are to be found in considerable number, proving that its use was more or less constant in this respect. To determine, then, whether or not the blacker specimens of the ancient writings contained indigo in any of its forms was most important, and the plan adopted most simple. Specimens of writing in ink of which the manufacturer's name was known as well as his formula and only thirty years old showed evidence of considerable "browning;" some of them when tested in juxtaposition with those of from fifty to one hundred years old which had turned completely brown, gave approximately the same results, and differentiated largely from the results obtained from jet black specimens of eighty to five hundred or more years of age. In a number of the browner ones indigo was found to be present while in many of the black ones it was not, demonstrating that the reason for the continuing blackness of the older inks is not due to an added color or pigment of any kind and furthermore that the "Stark" and corresponding ink formulas after the test of TIME did not retain their original blackness but deteriorated to a brown color; moreover, that their purpose as in the present day was to give an agreeable and immediate color result, a free-flowing ink, and to cheapen the cost of manufacture when compared with that of an unadulterated tanno-gallate of iron ink.

No disagreement being now possible as to the lasting color virtues of a properly proportioned tanno- gallate of iron ink WITHOUT an "added" color or pigment, there remained the sole question as to the vehicle utilized to hold this combination in suspension and whether or not it had to do with the continuing blackness of the older inks.

The answer must lie between the vegetable product known as gum and the animal product known as gelatine. The first disintegrates, quickly absorbs moisture and gradually disappears, while gelatine (isingla.s.s) "contains under conditions 50% carbon, although its molecular formula has not yet been determined. It cannot be converted into vapor and does not form well-defined compounds with other bodies; it is insoluble in alcohol which precipitates it in flakes from its aqueous solution. It is also precipitated by tannin, which combines with it to form an insoluble non-putrescible compound. Gallic acid, however, does not precipitate it." (Bloxam.)

Possessing an undisturbed and complete history it was the very substance employed long before the discovery of gall ink, and is found present in the earliest specimens of the "Indian" inks which remain to us.

It must now be evident that there can be no material difference of opinions as to what has been so clearly and conclusively established, viz. that ink which contains a base of tanno-gallate of iron (without "added" color) is a permanent ink, and the length of its durability and continuing pristineness can be disturbed only by inferior quality of const.i.tuents, wrong methods of admixture and its future environment. Hence any black ink with this combination missing is of no practical value whatever either for record or commercial uses.

"Indian" ink, except for specific purposes, belongs to the great past and will so continue with its virtues unchallenged and proven, until some solvent is discovered for the carbon which forms nearly the whole of its composition, at which time THE perfect ink can be said to have been discovered.

CHAPTER XVII.

INK PHENOMENA.

CONDITION OF INK WHEN FIRST PLACED ON PAPER--ITS METAMORPHOSIS AND AFFINITIES--IGNORANCE OF THE FORGER AS TO ITS ORIGINAL ENVIRONMENT--TREATMENT OF OLD INK MARKS--HOW PAPER MAY DISCOLOR INK--THE USES OF ACID IN INK--VEHICLES TO HOLD INK PARTICLES AND PRESERVE THEM--INKS FIVE CENTURIES OLD DO PRESERVE THEIR GLOSS--SOME CAUSES OF INK DISINTEGRATION--WHEN INK BECOMES IRRESPONSIVE TO THE ELEMENTS-- DEMONSTRATED TRUTHS ABOUT INK CONSt.i.tUENTS AND COLOR PHENOMENA--NATURAL EVOLUTION OF AN INK MARK--LENGTH OF TIME REQUIRED TO BECOME BLACK--FIRST INDICATIONS OF AGE--DISAPPEARANCE OF INK QUALITIES--ARTIFICIAL AGING OF INK--TESTS FOR IT AND HOW TO CONFIRM THEM--BLEACHING AND REMOVAL OF INK FROM PAPER CRIMINALLY CONSIDERED-- CHEMISTRY OF SUCH MARKS--THEIR RESTORATION-- VARIATIONS IN METHODS WHICH CAN BE EMPLOYED.

ALL inks when first placed on paper are of course in a fluid state. Gradual evaporation of moisture causes a change not only in color but in the case of the iron and gall inks, in their chemical const.i.tution, being immediately affected by their environment, whether due to the character of the paper on which they rest, the kind or condition of the pen used, or most important of all, the elements. Those who use the black inks and chemical writing fluids will have noticed these characteristics. The pale brown, blue or green as first written, and the gradual change after a short period to an approaching blackness, are reactions due largely to atmospheric conditions, the oxygen uniting with that for which it has affinity and instantly beginning with TIME to make its march, producing natural phenomena, which can be only superficially imitated but never exactly reproduced. When we further take into consideration that the forger cannot always know of the circ.u.mstances which surround the placing of original ink on paper and that be cannot manufacture the TIME which has already elapsed, it is not strange that attempted fraud can often be made evident and complete demonstrations given of the methods employed.

With the pa.s.sage of time, the particles in some inks which are held together on the paper by gummy vehicles, commence to disintegrate and change from intense black to the brown color of iron rust, the "added" color which of itself is fugitive in character, soon departs; the vegetable astringent separating from the iron salt decays gradually and disappears and finally terminates in a mere stain or dust mark which can be blown off the paper. Sometimes, the written surface of such paper can be treated by carefully moistening it with a decoction of nut-galls or its equivalent in the presence of a weak acid, then if any iron be present, a measurable degree of restoration of color will ensue and remain for a short period.

Again, the discoloration of an iron ink may be due to the character of the paper; if of the cheaper grades and the bleaching compounds employed in their manufacture are not thoroughly washed out, then the ink not only begins to absorb oxygen from the atmosphere but the chlorine in the paper attacks it and the process of destruction is thereby hastened.

The introduction of acid into ink has two purposes, one to secure more limpidity, and the other to cause it to penetrate the paper and in this way bind together the const.i.tuent particles of both ink and paper. Most of the chemical writing fluids of this decade carry a superabundance of acid in their composition, which in time will burn through the paper and ultimately destroy it.

All tanno-gallate of iron inks require some vehicle to hold their particles in a state of suspension, otherwise there would be precipitation and such an ink could not be used. To meet this requirement a variety of gums are employed by manufacturers, gum acacia being the princ.i.p.al one. Its purpose is threefold--as before stated, to hold the ink particles in suspension--to prevent the ink from flowing too rapidly, and after drying WITHOUT blotting, to act as an envelope to encase the now fixed ink and prevent or interfere with its absorption of an excess of oxygen.

The longer these latter conditions obtain the longer will the ink retain its pristineness, its durability and permanence. The "time proved" ink-written specimens of five hundred years or more ago which continue to retain their original intense black color and "glossy" appearance, do not, however, yield any evidence of the use of vegetable gums in their composition.

Where such instances have been noticed the gloss is invariably missing. But, where ANY gloss is present, it was and is because of the employment of isingla.s.s (fish-glue) as the vehicle to hold the ancient ink particles.

Hence the variations of color seen in ancient paper writings, as already stated, were due not only to possible imperfect admixtures of the component parts of the inks, but to the use of vegetable gums in their preparation. In the course of time these have been absorbed by moisture which hastened disintegration, causing a gradual disappearance of their original blackness and gloss and finally a return to the rusty color of oxidized iron.

It therefore follows, my observations and deductions being correct, the older a writing made with tanno-gallate of iron ink, where isingla.s.s is the binder, and which has not been "blotted," the harder and more impervious and irresponsive it becomes to the action of the natural elements or of chemical reagents.

The truths demonstrated in this proposition cannot be denied. They fortify as certain that a properly proportioned mixture in water of an infusion of nut- galls or gallo-tannic acid and sulphate of iron, with isingla.s.s as the vehicle to bold the particles in a state of suspension, if written with on good paper and allowed to dry without blotting, in a short time becomes encased or enveloped in such vehicle, which is thereby rendered substantially insoluble and absolutely prevents any extensive oxidation. Also, as a further consequent result, there is chemically created an unchangeable and continuing black color more permanent and durable than the substance on which it appears.

With a sample of standard commercial chemical writing fluid, write on "linen" paper without blotting it; in thirty hours, if exposed to the air and from three to five days if kept from it, the writing should have a.s.sumed a color bordering on black; it becomes black at the end of a month under any conditions, and so continues for a period of about five or six years, when if examined under a lens of the magnification of ten diameters, there will be a noticeable discoloration of the sides or pen tracks which slowly spreads during a continuing period of from ten to fifteen years, until the entire pen marks are of a rusty brown tint. A species of disintegration and decay is now progressing and when approximately forty years of age, has destroyed all ink qualities.

If, however, "chemical writing fluid" is first treated by exposure to the fumes of an ammoniacal gas, a "browning" of the ink occurs, not only of the pen tracks but of the entire ink mark. If examined now with a lens, the ink is found to be thin enough to permit the fibre of the paper to be seen through it, thus indicating artificial age. Furthermore, if a 20 per cent strength of hydrochloric acid be applied, the "added"

color (usually a blue one) is restored to ITS original hue; alike experiment on "time" aged ink gives only the yellow brown tint of pure gall and iron combinations, the "added" color having departed caused by its fugitive characteristics. Again, if a solution of chlorinate of lime or soda be applied, the ink mark is instantly bleached, where in the case of honest old ink marks, it takes considerable time to even approximate a like result.

To confirm the chemical tests which may be employed in the determination of the artificial aging of ink marks, photographs made by permitting light to transmit through the paper and to interfere with its rays by filtering them through a "color" screen containing orange and some green, will indicate the presence of a fugitive substance in the ink, usually the "added" color employed in its manufacture.

The process of bleaching or "removal" of ink marks from paper is frequently employed in the attempted eradication of words or figures and the subst.i.tution of others on monetary instruments, commonly called "raising." Its purpose is usually a criminal one and some observations as to the modus operandi and its chemistry are not out of place here.

Ink marks made with a compound consisting of the combination of iron and an infusion of galls or its equivalent (a tanno-gallate of iron ink), as treated with certain chemicals, change from a compound with color to a chemical compound, with no color. Nothing has in fact been absolutely removed or eradicated, but it is a mere change of form, a sort of re-arrangement of the particles, the ingredients which formed the original color being still present, but in such a condition that they are invisible to the eye. A restoration of the invisible ink marks so that they can be observed, becomes possible by the use of chemical reagents and is the reverse of the one of erasure or bleaching, and changes the const.i.tuents again into a compound which has color from the one which had none. It does, not, however, reproduce the exact composition originally existing. Such a reagent simply goes to the basis of the material as first used, takes up what was left and reforms the particles sufficiently to make them abundantly recognizable. An apt ill.u.s.tration of these chemical changes of color is found in what is known as the phenolphtalein test solution, which is colored deep purplish-red by alkali hydrates or carbonates, and then by the addition of an acid rendered colorless, to be again reddened by an over- plus of the alkali and so on ad infinitum.

A popular material for the purpose of making chemical erasures is chlorinated lime or soda, which becomes more active by first touching the ink mark to be removed with a one half strength solution of acetic acid; this hastens the liberation of chlorine gas, THE active agent which causes the "bleaching"

to take place. Hydrogen peroxide, also a bleaching compound, is less rapid in its action than chlorinate of soda; the same may be said of combinations of oxalic and sulphurous acids.

The most effective re-agent for the restoration of a chemically "bleached" iron ink mark is the sulphide or sulphuret of ammonia (it has several names). This penetrating chemical blackens metals or their salts, whether visible or not, if brought together. It must not be used by direct contact, the best and safest plan being to place a quant.i.ty in a small saucer, to be set on the floor of a closed box; to fasten to the box lid the specimen to be operated on; in this way the restoration is due to the fumes of the chemical and a possible danger of destruction of the specimen much lessened, especially if the marks are very light or delicate ones. The restoration of color under particular conditions may also be obtained by treatment with tannic acid, pota.s.sium ferro-cyanide (acidulated) or a weak solution of an infusion of galls.

CHAPTER XVIII.

INK CHEMISTRY.

SOME OBSERVATIONS AS TO CHEMICAL EXAMINATION OF INK MARKS BY ALLEN--ERASING OF INKS BY CHEMICAL MEANS--APPROVED CHEMICAL TESTS IN THE ASCERTAINMENT OF INK CONSt.i.tUENTS.

A COMPILATION of the methods of Robertson, W. Thompson (Lord Kelvin), Irvine, Wislar, Hoffman and others, relative to the chemical examination of ink marks, is to be found in "Allen's Commercial Organic a.n.a.lysis." Their experiments, however, date back many years ago, a few of them before the time of the use of the "anilines" for added color. The so-called "alizarin" ink referred to has now become obsolete.

The following is the citation in part:

"In chemico-legal cases it is sometimes of importance to ascertain the nature of the ink used, to compare it with specimens of writing of known history, and to ascertain the relative ages of the writings. A minute inspection should first be made with a magnifying power of about 10 diameters, and any peculiarities of color, l.u.s.tre, shade, etc., duly noted, and where lines cross each other which lie uppermost. The examination is often facilitated by moistening the paper with benzine or petroleum spirit, whereby it is rendered semi- transparent. The use of alcohol or water is inadmissible.

"Valuable information is often obtainable by treating writing or other ink-marks with reagents.

Some inks are affected much more rapidly than others, though the rate of change depends greatly on the age of the writing. Normal oxalic acid (63 grammes per litre), or hydrochloric acid of corresponding strength, should be applied to a part of the ink marked with a feather or camel-hair brush (or the writing may be traced over with a quill pen), and the action observed by means of a lens, the reagent being allowed to dry on the paper.

Recent writing (one or two days old) in gallic inks is changed by one application of oxalic acid to a light gray, or by hydrochloric acid to yellow.

Older stains resist longer, in proportion to their age, and a deeper color remains. Log-wood ink marks are mostly reddened by oxalic acid, and alizarin marks become bluish, but aniline inks are unaffected. With hydrochloric acid, logwood ink marks turn reddish or reddish-gray, alizarin marks greenish, and aniline ink marks reddish or brownish-gray. The treatment with acid should be followed by exposure to ammonia vapors, or blotting paper wet with ammonia may be applied.

Thus treated, marks in logwood ink turn dark violet or violet-black. The age of ink marks very greatly affects the rate of their fading when treated with dilute ammonia, the old marks being more refractory. The behavior of ink marks when treated with solution of bleaching powder is often characteristic, the older writings resisting longer; but unless the reagent be extremely dilute, writings of all ages are removed almost simultaneously.

Hydrogen peroxide acts more slowly than bleaching solution, but gives more definite results. After bleaching the mark by either reagent, the iron of the ink remains mordanted on the paper, and the mark may be restored by treatment with a dilute solution of galls, tannic acid, or acidulated ferro- cyanide. The same reagents may be used for restoring writing which has been faded from age alone.

"When ink marks have been erased or discharged by chemical means, traces of the treatment are often recognizable. After effecting the erasure the spot is often rubbed over with a powdered alum or gum sandarac, or coated with gelatin or size.

The bleaching agents most likely to have been used are oxalic, citric, or hydrochloric acid, bleaching powder solution, or acid sulphite of sodium.

Moistened litmus paper will indicate the presence of a free acid, and in some cases treatment with ammonia fumes will restore the color. The presence of calcium, chlorides, or sulphates in the water in which the paper is soaked will afford some indication of bleaching powder or a sulphite having been used. Pota.s.sium ferro-cyanide will detect any iron remaining in the paper. Exposure to iodine vapor often affords evidence of chemical treatment, and other methods of examination readily suggest themselves."

M. Piesse, in the Scientific American, is authority for a method of removing ink, found on "patent"

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