A critical study of old manuscripts and treatises on painting from classical antiquity to 1850 has made it possible to produce a reference manual of more than 25 hide glues and one bone glue from cattle, sheep, elk, rabbit and fish. It became obvious that the technical properties of animal glue vary with the kind and amount of fat it contains. The fatty acids which can be analyzed by gas chromatography can be used as a fingerprint of what kind of animal and/or tissue the glue comes from. Since it is only necessary to calculate the relative composition of two saturated fatty acids, namely 16:0 and 18:0 (palmitic acid and stearic acid) this kind of analysis can be performed when the glue has aged and the unsaturated fatty acids are more or less degraded. This method of analysis is the main subject of this paper. The project was a cross-scientific one entitled Old Materials and Techniques in Painting . The cooperating institutions were the Institute of Art History and the Chemical Center, at the University of Lund, Sweden. -- CAL