ANTIFUNGAL PROTECTION AND SIZING OF PAPER WITH CHITOSAN SALTS AND CELLULOSE ETHERS. PART 1, PHYSICAL EFFECTS
MARIA DEL PILAR PONCE-JIMÉNEZ, FERNANDO A. LÓPEZ-DELLAMARY TORAL, & EZEQUIEL DELGADO FORNUÉ
This article examines materials for sizing mold-damaged paper supports. The work is divided into two parts. The first part deals with the sizing behavior of chitosan salts and cellulose ethers on the physical and mechanical properties of Whatman no. 1 filter paper. The second part covers the antifungal protection offered by these same substances against a select group of fungal strains.
The paper conservator is sometimes confronted with the problem of restoring documents that have fungal deterioration. A wide variety of fungi inhabit libraries and archives, and many are resistant to changes in humidity and temperature. The enzymes in fungi gradually destroy the cellulose, hemicellulose, lignin, and other substances that make up documents, books, and works of art on paper.
The depolymerization of cellulose results in visible deterioration in the form of staining and weakened fibers. Therefore, the paper conservator who wishes to recover the object must add structural stability and then reinforce it. Even after fumigation, dormant and airborne spores may recontaminate the paper, so sizing and preservation against recurring attacks are necessary. The conservator may also apply an auxiliary backing so the paper can be handled safely without risk of further damage. It is important for the conservator to explore solutions and suggest those that are most effective in conserving the fungidamaged paper-based materials while simultaneously protecting the paper base against future fungi and bacteria attacks.
Various methods can be used to solve the problem of paper weakening. Many polymers applied as a coating can improve the strength of paper, although, over time, micro-organisms can still damage materials treated in this fashion. There are some products, however, that are both effective for sizing and resistant to fungi attack. For example, polyethylene-coated paper shows no evidence of micro-organism growth, and parylene has been shown to protect paper and improve its biostability (Dobroussina et al. 1996). A multitude of studies have revealed a variety of efficacious materials. This article will evaluate chitosan, which has not been previously analyzed for conservation use.
Chitosan is a substance obtained by deacetylation of chitin, the principal component of many living forms, including fungi, insects, and crustaceans (Muzzarelli 1977). Chitosan is a whitish, amorphous powder with a crystalline structure similar to that of pure chitin. It is an interesting product because of its properties, abundance, and multiple uses, but until now there have been no investigations into its application to paper conservation.
Cellulose ethers have been widely studied as consolidating agents for paper (Feller and Wilt 1990), obviating the need to describe their advantages and disadvantages in this article, though it is noteworthy that cellulose ether–treated papers can be prone to fungi attack, depending on storage conditions. In this study, we compare some properties of Whatman no. 1 filter paper samples consolidated with 2% aqueous solutions (w/v) of three cellulose ethers (sodium carboxymethylcellulose [CMC], methylcellulose [MC], and hydroxypropylmethylcellulose [HPMC]) and with three 2% aqueous solutions (w/v) of chitosan salts (acetate [AQ], butyrate [BQ], and propionate [PQ] of chitosan).