The applicability of penetrant inspection processes to registration of deterioration symptoms of ancient stained glass surfaces was examined. The examined surfaces were studied in parallel experiments by macro-and microscopic observations and by profilographic measurements. Commercial penetrant preparations were used. It was shown that penetrant inspection process allows a comparison of the deterioration symptoms on different stained glass surfaces. Penetrant inspection process is especially suitable in studying the porosity and roughness of glass surfaces. It also gives information on the type of deterioration symptoms, their distribution and density as well as on the fine network of surface fissues. The fluorescent penetrants have been shown to give much better results than solvent removable dye penetrants. The best were obtained with solvent removable fluorescent penetrants (e.g. 985-P2, Ardrox Ltd. , ZL-3, Magnaflux Corp.) without the use of any developer. The developer was useful only in examination of grisaille flaws. The best reproducibility of the results was obtained with post-emulsifiable penetrants, however, many symtomps of deterioration were not then detected. Glass surface relative porosity can be estimated by the use of solvent removable fluorescent penetrants in drop test. A complex examination of deterioration symptoms of stained glass surfaces should include the registration of surface deterioration with the use of fluorescent penetrants without a developer or with its use for grisaille surface, as well as the results of a drop test with a fluorescent penetrant to measure the surface porosity.