The purpose of this project is to synthetize and to characterize green and yellow pigments used by the painters of Catalan Gothic period. The concerned pigments are the green, yellow typical 1 (which the chemical formula is Pb2SnO4) and yellow typify 2 (which the chemical formula is Pb (Sn, If) O3). To synthetize them, it is necessary to know their chemical compositions. It is so possible to reproduce pigments. Once pigments were reproduced, the objective was to characterize them. For that purpose, the spectroscopy in infrared was used at first. We put the sample in the form of capsule by applying it a strong pressure after the credit note to mix in some oxide of bromide. Secondly, the diffraction by X-rays used too. Pigments were sent in Grenoble, to the European Synchrotron Radiation Facility. It was thus possible to characterize them and to know their exact compositions. Other part of this study was to observe the reaction of these pigments mixed on one hand in some oil of it in and on the other hand to egg yolk according to time.