"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 CONSTITUENTS 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 constitution, 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 circumstances 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.