The present announcement is about the physicochemical study of the copy letters from the Heinrich Schliemann archive, located in Gennadius Library, Athens, Greece. The goal of this research is the suggestion of a methodology, based on the use of non-destructive diagnostic means, for the validation of the maintenance situation of the copy letters and for the record of the characteristics of the various types of inks that were used during the period 1845 and 1890. Chosen pages from the archive were studied with the help of ultraviolet reflectance photography, b/w and coloured fluorescence photography and infrared reflectography, in normal and macro modes from both sides of the document. The processing of the results was based mainly on the optical behaviour of the copy letters in the various wavelengths, in relation to their oxidation state and the quality of the copy, in order to classify the inks according to their characteristics.