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

概要

Conservation and Restoration of Western Paper

considered a direct threat to the permanenceof the paper substrate. However, as iron (III)ions are considered a future hazard, becausethey can be easily reduced to iron (II) ions,the test can be modified to also identifyiron (III) ions. 15 To modify the test, it isnecessary to reduce iron (III) ions to iron (II)ions, for the indicator bathophenanthrolineto react with them, so a reducing agent isused on the test paper once the result foriron (II) ions has been registered.Thus, inks with higher concentrations ofiron (II) ions in the bathophenanthrolineindicator paper are potentially more corrosivethan inks with lower concentrations. In theirproposal for risk assessment, Tse and Wallerconsider an approximate concentration of25 ppm of iron (II) ions as a high risk ofink corrosion. 12 So, from that approximateconcentration it is riskier to perform anyaqueous treatment on the document, unlessa chemical stabilization treatment is alsoconsidered.D. Iron (II) ion test strip color chart 16This color chart, developed at the CanadianConservation Institute (CCI), is usedwith the iron (II) ion indicator paper, todocument the result of the test, comparingthe color obtained in the indicator paperwith the color strips of the chart. It consistsof four magenta color strips, in whichthe tone is intensified as the estimatedconcentrations of iron (II) ions increases.The chart can be obtained directly from theCCI.Risk groupsFrom the study of the mentionedinformation generated by research indifferent countries, and the analysis andassessment of their own collections, theCanadian specialists propose four riskgroups, in which a document with iron gallink can be classified. 12? Group risk I: No immediate risk.? Group risk II: Risk of ink fading.? Group risk III: Risk of ink corrosion.? Group risk IV: Risk of mechanicaldamage and loss of material.In addition to the risk assessmentmodel, Tse and Waller propose anothermodel for the control options for theidentified risks of the determined grouprisk (I to IV), including both chemical andmechanical stabilization treatments, pluspreventive conservation measures. Finally,they present a treatment options model,which incorporates aspects evaluated in theprevious models to facilitate the decisionmaking process. 12In my experience, the Canadian modelshave been of great help in order tounderstand the priorities in the assessmentof documents with iron gall inks. Theapplication of these models implies theconsideration of the current and potentialrisks; therefore, they provide an excellentoverview of all the variables that caninfluence ink corrosion. The Spanishtranslation of the three models (withpermission of the authors and the CCI)has been a big help for their application inMexico, and hopefully, it will be useful tooin other Latin American countries. 1152