Documents can be forged in various ways, most common of which is the addition of letters, numbers, words or even whole sentences. The comparison between the ink that was used in the original document and the ink that produced the disputed entry is possible through a series of chemical tests. In the relevant literature of Forensic document Examination a number of ink analysis methods is thoroughly described. Ink analysis provides the possibility to ascertain whether a disputed entry is produced by a particular type of ink. Further on, it can be determined whether two or more entries were made by the same or different type of ink.

Consequently, any additions in documents, which were produced with different ink in comparison to the original document, can be discovered.