ブックタイトルConservation and Restoration of Western Paper

概要

Conservation and Restoration of Western Paper

Conservation of Archival and LibraryPatrimony (ICPAL) Laboratory for theConservation of Library Materials, Rome) atthe Book and Paper Session of the AmericanInstitute for Conservation AIC Meetingin 2010 13 . Their search for an alternativemethod of wet- cleaning graphic art thatwould not alter topographical features―like surface texture, platemarks, and etched/engraved lines―led to early experimentswith gellan gum at ICPAL in 2003-2004.Gellan gum gradually releases moisture intoan adjacent substrate in a controlled way andleaves no residue. When used for cleaningor stain reduction, soluble deteriorationcomponents are transferred to the gelthrough osmosis. Iannuccelli and Sotgiureported on various treatments carriedout with gellan gum, including backingremovals, enzyme delivery, deacidification,and reductive bleaching. Inspired by theirfindings, conservators at LAC have usedgellan gum in a variety of treatments onobjects ranging from a book and threedimensionalmap to a vintage paper dress.The use of polysaccharide-based rigid gelsas the basis for highly controlled cleaningsystems for painted surfaces was firstintroduced by Richard Wolbers in 2000 14 .Altering pH and incorporating a range ofother ingredients, like surfactants, chelatorsand enyzmes can produce tailor-maderigid gels for specific cleaning applications.Paper conservators have customarily usedgels based on cellulosic thickening agents,like methyl cellulose, ethyl cellulose, andsodium carboxy methyl cellulose over thelast 40 years as poultices for cleaning, or formixing with other active ingredients, likebleaches and enzymes. The application ofrigid gel treatment systems to paper artifactsis of great interest to paper conservators,permitting a superior degree of control bylimiting capillary action and the movementof cleaning agents held within the gel matrixduring the course of treatment.Gellan gum finds application asa thickening or gelling agent in thebiomedical, pharmacology and foodindustries, and is biodegradable and nonhazardous(Photos21a-c). The generalchemical structure is a straight chain of fourlinked monosaccharides (ie: simple sugars),including one molecule of rhamnose (plantderivedsugar), one molecule of glucuronicacid, and 2 molecules of glucose (Diagram 7).Studies conducted by by Sottgiu andIannuccelli of various rigid gellan gels(Phytagel gellan, Gelrite and Gelzan CM)concluded that Kelco gellan gum was themost effective and economical product 15 .In their tests gellan gum also comparedfavourably to agarose gel, with highertransparency and greater water retentionproperties.Gel formation is influenced bytemperature, concentration, thickness of thecast layer and by the presence or absenceof mono or bivalent cations. Gellan gumis available in two grades: high and lowacyl content, which form soft and hardgels respectively. Deacylated, or low acylcontent gellan gum is used for conservationapplications. It forms a stronger gel, andsets at a much lower temperature range?between 30 and 50 degrees Celsius?71