Over 108 samples of mural paintings from Teotihuacán, México, were studied by scanning electron microscopy, optical microscopy and X-ray diffractometry. The results show a sequence in the techniques employed to produce the mural painting's supporting plasters -made of lime and different sands. The technical stages found can be used as archaeological data to help understand the continuous evolution of 800-year mural paintings. The consequences of our study are discussed in detail.