Subsoil effects on superficial fungal growth

(Some words are not readable in abstract) The effect of a nutritive subsoil on fungal disfigurement of water-borne acrylic painit ..... experimentally assessed. The experimental procedure included scanning electron microscopy of mouldy samples as well as comparative tests of fungal resistance of ... paints on nutritive gypsum plaster. From microscopic examination of the tested sample ... concluded that fungal defacement is a pure surface phenomenon ; no penetration of ...paint and unfinished gypsum was observed. These observations agree with previous examination of affected spots of finished plasters in a dutch dwelling. Fungal resistance tests were performed in small incubators, at relative humidities of 97 % and 86 %. It was concluded that subsoil nutrients may influence superficial growth remarkably. Furthermore, it was obvious that the susceptibility of a multilayered finishing system should not be judged by testing constituent layers separately. Some hypothetical explanations are discussed. With respect to the fungal species involved, the experiments confirm xerophilic moulds may well be causing fungal disfigurement of indoor finishes at a relatively low air humidity of 86 %. Contrary to 97 %, no contaminant species were observed. The fast discolouration of gypsum demonstrates that a minor water content is sufficient for fungal growth. Considering the fact that hyphae are not able to penetrate pores in the hygroscopic range, this indicates water adsorption is important in water supply of the fungus.