Study of Disappearing ink Writings on Different Types of Documents | ||
| Egyptian Journal of Chemistry | ||
| Article 25, Volume 63, Issue 2, February 2020, Pages 653-668 PDF (3.21 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ejchem.2019.13062.1816 | ||
| Authors | ||
| Nora M. Hilal* 1; Rania H. Twfiq2 | ||
| 1Chemistry depatment.faculty of science,al_azhar University,Cairo | ||
| 2Department of Forgery and Counterfeiting Research, Forensic Medicine Authority, Ministry of Justice, El-Sayeda Zeinab, Cairo, Egypt 11461. | ||
| Abstract | ||
| Disappearing inks are used in textile industry such as dressmaking crafts and as a kind of teaching material; for example, printed questions are visible and the spaces for an answer exhibit invisible disappearing ink. The answers only become visible using a coloring assistant. This research was conducted on the preparation of disappearing inks using different concentrations of thymolphthalein (Th-ph) and O-Cresolphthalein (O-Cph). The prepared inks were applied to different types of handwriting papers. It was found that the handwriting stability increased by increasing thymolphthalein (Th-ph) and O-Cresolphthalein (O-Cph), or alkali concentration. Deciphering of the faded documents was evaluated by different methods. Commercial paper C2 surfaces gave the more handwriting stability than other paper, the order of stability were C2 ≥ C1 > Azhar >Xerox > C3 >C4 > Edfo. All the faded documents were visible when treated with alkaline solution. When the faded documents surfaces are exposed to the thermal effect there is no change in all the faded documents. Disappearing inks have been used in different fields, but it may be abused in forgery and counterfeiting. | ||
| Keywords | ||
| Forensic medicine; questioned documents; disappearing inks; fading time; thymolphthalein; O-Cresolphthalein | ||
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