This treatment fixes the appearance of the spread lines and colored spots in the space that has been washed and renders more noticeable the stain caused by a partial sizing.  In this manner apparently white paper on which at first no traces of characters could be found showed a yellow tinge, denoting the presence of previous writing, and on the application of gallic acid and an infusion of nut-galls became sufficiently distinct to permit the erasure and forgery to be detected.

When an erasure is made on the surface of such a paper, the mineral and organic materials of the sizing and loading are removed, and the fibres of the paper which they unite are deranged in form and position.  Such a surface exhibits invariably the teased-up ends of the fibres, and generally shows by the agreement in their direction in what way the scratching was done.

Even in cases where a substitute for the sizing has been so successfully added that no change in color or surface is observable, the fibres will show by their unusual positions that they have been disturbed.  When an attempt has been made to write over the place without sufficiently restoring the sizing, the effects can be seen in the running of the ink between the fibres and the staining of the body of the paper to a considerable depth from the surface and to a considerable distance from the spot.

Erasures in parchments produce prominences on the opposite side of the sheet.  The ink placed upon such erasures has a peculiar bluish tinge.  It happens at times that a whole page is taken out, either by scratching or rubbing with pumice (which was the practice in the eleventh century, when a parchment became so valuable that it was common to keep up the supply by erasing the writing on old parchments) or by washing.

When the latter method was used, the writing as in palimpsests can be made to reappear by warming.  The parchment can be either laid on a hot plate or pressed with a hot flatiron between two sheets of paper.

Where the supposed writer of a document was a bad or careless penman the interlineations or additions are generally distinguished from his handwriting, which they simulate, by greater clearness and precision, as has been said above; for when a man will risk being sent to jail for forgery it is not likely that he is willing to lose any prospective advantage which his felony will bring him by lack of distinctness in the characters by means of which it is perpetrated.

Considering the number of fraudulent additions or interlineations which are constantly made, the number of mistakes in spelling or in following the method employed by the supposed writer in forming the same words is surprisingly great.  Several instances are recalled where the name of the supposed writer was not only mispelled but spelled in two different ways in the same instrument.  It occasionally seems as if the forger’s attention is so earnestly directed to overcoming the difficult parts of his task that he neglects the simpler and more obvious parts.  A forger generally leaves some telltale marks to make his detection certain.