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ASCERTAINMENT OF A CORRECT INK FORMULA THE WORKOF OVER A CENTURY--CHARACTER OF THE EVIDENCE WHICH ESTABLISHES IT--THE INVESTIGATIONS OF THE AUTHOR IN THIS DIRECTION AND COMPARISON WITH THOSE OF COMMISSIONER SWAN--ELIMINATION OF THE "ADDED" COLORS AND THEIR ORIGIN-DISCUSSION OF THE RELATIVE MERITS OF LAMPBLACK, MADDER AND INDIGO--THE DURABLE VIRTUES OFINDIGO WHEN EMPLOYED ALONE--CAUSE OF THE BROWNING OF INKS--LONGEVITY OF INK DUE TO VEHICLE WHICH CARRIES IT--WHEN PERFECT INK WILL BE INVENTED.

TO ascertain the correct formula of a substantially permanent ink, as we have learned, has been the aim during a century or more, of able chemists, manufacturers and laymen. Their experiments and study of ancient and modern documents all point unerringly in the direction of an ink containing iron and galls.

Accumulated evidence may be said to establish itself in the light of investigation and experience and becomes more and more a certainty when considered, reviewed and discussed in connection with a chronological history of the "gall" inks since they came into semi-official and other uses centuries ago.

Descriptions of MSS. containing ink writings hundreds of years old, many of them as legible as when first written, are silent witnesses whose testimony cannot be assailed. Such information when assembled together minimizes many of the conditions which have existed and interposed in preventing during the last four decades a general adoption or re-adoption of such a tanno-gallate of iron ink, the lasting qualities of which some of our forefathers estimated would, and as we know have stood the test of time.

Assuming this character of ink to have been employed in past centuries, the cause or causes for the differentiations in respect to color and durability become of paramount importance.

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 analytical and microscopic examination of ancient with ancient and modern with modern documents 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 documents 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 document 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.

Assuming a second premise was to assert that the inks employed in the writing of these documents 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 classes: those possessing tannin and color-yielding materials and those containing only a color-yielding material. Many of the first class have been used in the manufacture of ink both with infusions of nut-galls or alone, while but very few of the second class have been used for either purpose.

The decomposing action of light, oxygen and moisture on many of each class 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 assimilate perfectly with other constituents 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.