Over a 10-year period, 15 paintings by Claude Lorraine and Gaspard Dughet were examined by stereomicroscopy, polarized light microscopy of paint cross-sections, microchemical analysis, electron microprobe analysis with x-ray diffraction, gas-liquid chromatography, and scanning electron microscopy in an investigation of blanching. Although Dughet's paintings have only one or two paint layers while Claude's have many superimposed layers, both painters used a mixed, water-in-oil medium and hydroscopic pigments. The investigators examined the holes and pits in the paint layers, but found that although numerous pits make paint films look more opaque or white, porosity alone cannot explain blanching. They found that paintings with blanching had inherent paint film defects which were worsened by cleaning and relining. The study is accompanied by many photographs and a chart providing a detailed comparative analysis of the paintings.