This is a Python code associated to a data treatment procedure first described as "Preconcentration" in the thesis : "Caractérisation physico-chimique in situ des matières colorantes à base d’oxydes de fer et de manganèse des parois des grottes ornées, ex. Font-de-Gaume (France)", Antoine Trosseau, 2021. This code allow to quickly perform a data treatment of X-Ray Fluorescence data used in the Preconcentration procedure. The data treatment consists in calculating the thickness index Tau, weigth the corresponding spectra by their Tau, calculate a cumulative sum of these spectra, normalize by the summed Tau. This treatment can be performed on intensity data provided by the user, or on raw spectra.