Antifungal treatment of paper with calcium propionate and parabens: Short-term and long-term effects

A deacidifying/antifungal mixture composed of calcium propionate, methylparaben and propylparaben was tested against Aspergillus niger, Cladosporium cladosporioides, Chaetomium globosum, Penicillium chrysogenum and Penicillium corylophilum. The preventive treatment of paper samples resulted in a complete fungal growth inhibition on 4 of the 5 tested species. The antifungal properties of the formulation remained unaffected for a minimum period of one year. The disinfecting treatment with the mixture led to a total elimination of all tested fungal species. The effects of the tested formulation on paper were evaluated in terms of pH, colourimetry, folding endurance, FTIR and XRD, using moist heat artificial ageing. Aside from plain paper, paper previously colonized by A. niger was tested to evaluate the potential of the formulation in preventing deterioration caused by fungal metabolites. In plain paper, an effective deacidification and long-term prevention of mechanical resistance loss were achieved, although a slight paper discoloration occurred. On previously colonized by fungi, the treatment effectively prevented the deterioration caused by fungal metabolites.