Electron paramagnetic resonance is suggested for investigating museum pieces to obtain information on their microstructure. Analysis of EPR spectra shows that they are due to paramagnetic ions of manganese, iron and other elements that are components of the main material or impurities and radicals. Dependence of the EPR spectrum on different factors (light, temperature, radiation) has been investigated. Aging of substances has been connected with the presence of radicals. The EPR method is suggested for control of microstructural changes of the material on the electron level. The authors are interested in scientific contacts in the investigation of the EPR method.