To determine whether or not papers contain erasures the suspected document should be examined by reflected and transmitted light. Examine the surface for rough spots. Forgers after erasures frequently endeavor to hide the scratched and roughened surface by applying a sizing of alum, sandarach powder, etc., rubbing it to restore the finish to the paper.
Distilled water applied to the suspected document at the particular points under examination will dissolve the sizing applied by the forger. If held to the light the thinning will show. The water may be applied with a small brush or a medicine dropper. Water slightly warmed may be used with good results at times.
Alcohol, if applied as described for water, will act more promptly and show the scratched places. It may be well to use water first and then alcohol.
To discover whether or not acids were used to erase, if moistened litmus-paper be applied to the writing, the litmus-paper will become slightly red if there is any acid remaining on the suspected document. If the suspected spots be treated with distilled water, or alcohol, as already described, the doctored place will show, when examined in strong light.
Which of two inklines crossing each other was made first, is not always easy of demonstration. To the inexperienced observer the blackest line will always appear to be on top, and unless the examiner has given much intelligent observation to the phenomenon and the proper methods of observing it mistakes are very liable to be made. Owing to the well-known fact that an inked surface presents a stronger chemical affinity for ink than does a paper surface, when one ink-line crosses another, the ink will flow out from the crossing line upon the surface of the line crossed, slightly beyond where it flows upon the paper surface on each side, thus causing the crossing line to appear broadened upon the line crossed. Also an excess of ink will remain in the pen furrows of the crossing line, intensifying them and causing them to appear stronger and blacker than the furrows of the line crossed.
It is probable that ink and pencil alterations and erasures are more frequently made with a sharp steel scraper and ink-erasing sand rubber than otherwise. By these methods the evidence—first, the removal of the luster or mill-finish from the surface of the paper; second, the disturbance of the fibre of the paper, manifest under a microscope; third, if written over, the ink will run or spread more or less in the paper, presenting a heavier appearance, and the edges of the lines will be less sharply defined; fourth, if erasure is made on ruled paper, the base line will be broken or destroyed over the scraped or rubbed surface; fifth, the paper, since it has been more or less reduced in thickness where the erasure has been made, when held to the light will show more or less transparency. When erasures have been thus made the surface of the paper may be resized and polished, by applying white glue, and rubbing it over with a burnisher. When thus treated it may be again written over without difficulty. When erasures have been made with acids, there is a removal of the gloss, or mill-finish; and there is also more or less discoloration of the paper, which will vary according to the kind of paper, ink, and acid used, and the skill with which it has been applied. If the acid-treated surface is again written over, the writing will present a more or less ragged and heavy appearance, if the paper has not been first skillfully resized and burnished. It is very seldom that writing can be changed by erasure so as not to leave sufficient traces to lead to detection and demonstration through a skillful examination.
Upon hard uncalendered paper erasures by acid when skillfully made are not conspicuously manifest, nor when made upon any hard paper which has been "wet down" for printing, since the luster upon the paper would be thereby removed, and, so far as the surface of the paper is concerned, there would be no further change from the application of the acid. This applies to a wide range of printed blank business and professional forms.
A forgery consists either in erasing from a document certain marks which existed upon it, or in adding others not there originally, or in both operations, of which the first mentioned is necessarily antecedent to the last; as where one character or series of characters is substituted for another.
The removal of characters from a paper is effected either by erasure (seldom by pasting some opaque objects over the characters, painting over them, or affixing a seal, wafer, etc., to the spot where they existed) or by the use of chemical agents with the object of dissolving the writing fluid and affecting the underlying paper or parchment as little as possible.
If the erasure be effected by scratching or rubbing, this removes also the surface of the paper, which consists of some sort of "size" or paste with resin soap, which is pressed into the upper pores to give the paper a smooth appearance, and to prevent the writing fluid from "running," or entering the pores and blurring the edges of the lines.