Efficacy of dielectric barrier discharge (DBD) plasma in decontaminating Streptomyces colonizing specific Coptic icons

Eight Streptomyces isolates were collected from three deteriorated icons dated back to 18–19th centuries. Streptomyces isolates cause different deterioration symptoms such as disfiguration, blackening of red lead and thinning of linen fibers in the canvas. Dielectric barrier discharge (DBD) plasma were used in decontamination Streptomyces colonizing icons and a period 8 min was sufficient for decontamination of most isolated Streptomyces and the distance 3 mm was more effective than other distances. DBD plasma treatment for different periods (4, 8, 10 min) for different distances (3, 5, 10 mm) did not cause any visual chromatic alteration for irradiated pigments of red lead, cinnabar HgS, PbCO3, black carbon, copper acetate (CuCOOH, H2O), hematite, limonite and Egyptian blue. On the other hand, FTIR spectra indicated no modification in the structure of tested binder in the grounds. Finally, DBD plasma did not affect on the tensile strength of linen canvas.