The aim of the present study is the proposal of a non-destructive methodology for the identification of old inks used in Bycant ine and post Byzantine manuscripts. The proposed methodology relies on the recording of the optical behaviour of inks in the near infrared region (780 - 1250 nm) using infrared reflectography assisted by image processing techniques. Measurements of the diffuse reflectance of inks of known composition in the visible and near infrared region are performed with the help of the Kubelka-Munk theory. Identification of inks of unknown composition is achieved through the correlation of their reflectance factors with the reflectance factors of the standard inks using a mathematical simulation model. Because of the exceptional historical, artistic, religious and cultural value of Byzantine and post Byzantine manuscripts, the identification of their inks is a very useful tool contributing to the historical study, the documentation and the conservation of these documents of European and eastern culture. However, until now the application of analytical physicochemical methods for the identification of the chemical composition of inks requires the extraction of a quantity of some mg of the ink, that is in most cases undesirable. That' s why the proposition of a new non-destructive methodology for the identification of old inks is undoubtedly necessary. In the present study the attempt of a systematic and theoretically supported non-destructive methodology for the study and documentation of old inks is presented.